W 0 R L D M E T E 0 R 0 L 0 G I C A L 0 R G A N I Z A T I 0 N INSTRUMENTS AND OBSERVING METHODS REPORT NO. 40. WMO/TD-No

Transcription

1 I W 0 R L D M E T E 0 R 0 L 0 G I C A L 0 R G A N I Z A T I 0 N INSTRUMENTS AND OBSERVING METHODS REPORT NO. 40 WMO/TD-No

2 WORLD METEOROLOGICAL ORGANIZATION INSTRUMENTS AND OBSERVING METHODS REPORT NO. 40 WMO INTERNATIONAL RADIOSONDE COMPARISON - PHASE III - Dzhambul, USSR, 1989 Final Report by A. Ivanov, A. Kats, S. Kurnosenko, N. Nash, and N. Zaitseva WMO/TD-No

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4 -1- FOREWORD Phase III of the WMO Radiosonde Intercomparison was carried out from 1 to 26 August 1989 according to a recommendation of the ninth session of the Commission for Instruments and Methods of Observation (CIMO). This intercomparison of radiosondes used in Regions II and VI with link radiosondes used in the previous phases of the Radiosonde Intercomparisons was hosted by the USSR in Dzhambul. Phase I was carried out in 1984 in Beaufort Park, UK and Phase II in Wallops Islands, USA in The aim of these intercomparisons is to compare the relative performance characteristics of radiosondes used operationally. The results of the previous intercomparisons have been published in the Instrument and Observing Methods Report series as No. 28 (1986), No. 29 (1988) and No. 30 (1987). On behalf of CIMO I should like to express a deep gratitude to the management and staff of the USSR State Committee for Hydrometeorology for hosting this intercomparison and to all those who took part in the intensive campaign in Dzhambul. I am also very pleased to thank for their excellent work, including the evaluation and preparation of the results, the authors of this report and the members of the International Organizing Committee for this phase. I am confident that Members of WMO will find this report very useful, especially for improving the homogeneity of their upper-air data sets when several types of radiosondes have been used in the network to obtain the upper-air observations. (Jaan Kruus) President of CIMO

5 -2- Table of contents Table of Contents List of Tables List of Figures 1. INTRODUCTION 2. RADIOSONDES AND SYSTEMS USED IN PHASE III 3. FIELD PHASE FULFILMENT 4. METHOD OF ANALYSIS 5. COMPARISON OF SIMULTANEOUS MEASUREMENTS 5.1. Geopotential height 5.2. Pressure 5.3. Temperature 5.4. Relative humidity 5.5. Wind 6. COMPARISON AT STANDARD PRESSURE LEVELS 7. ANALYSIS OF TEMP MESSAGES 8. CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

6 -3- APPENDICES : A. Photographs of radiosondes B. Distribution of different systems at Dzhambul site C. Flight rig configuration D. The software description E. Radiation correction procedures F. The equation of the pressure calculation for radar radiosounding systems G. Data of the new Chinese radiosonde SMT H. Analysis of angle dependence on the radar measurements of height I. List of participants in the Phase III

7 -4- List of tables Table 2.1 Table 2.2 Table 3.1 Table 3.2 Table 3.3 Table 5.1 Table 5.2 Table 5.3 Table 5.4 Table 5.5 Table 5.6 Table 5.7 Table 5.8 Table 5.9 List of participating radiosondes. Sensors of radiosondes used in Phase III. The observational programme fulfilment. Dates, times and sun elevations of flights. Numbers of flights used for statistics at constant pressure levels at the times indicated. The reproducibility of geopotential height measurements. The reproducibility of pressure observations. Simultaneous nighttime temperature sensor comparisons, Finland-USA. Examples of simultaneous midday temperature sensor comparisons, Finland-USA. The reproducibility of temperature observations. Distribution of simultaneous humidity differences (% RH) relative to FIN within different temperature and humidity ranges. Means and standard deviations of humidity differences relative to FIN (% RH) in following pressure layers , , , hpa. Means and standard deviations of humidity differences relative to FIN (% RH) within different temperature and humidity ranges separately. Means and standard deviations of humidity differences relative to FIN (% RH) within different temperatures and humidity ranges.

8 -5- List of figures Fig Simultaneous height comparison data. Fig.S.S-5.8 Simultaneous pressure comparison data. Fig Simultaneous temperature comparison data. Fig Vertical profiles of relative humidity. Fig.5.16 Fig.5.17 Humidity sensor's perfomance. Vertical profiles of wind parameters. Fig.5.18 Scattering diagrams of wind data differences for time 18. Fig.S.19 Histograms of wind differences for time 18. Fig.5.20 Scattering diagrams of wind data differences for time 06. Fig.5.21 Histograms of wind differences for time 06. Fig Geopotential height differences and standard deviations at standard pressure levels. Fig Temperature differences and standard deviations at Fig.7.1 standard pressure levels. Time variations of air temperatures (from TEMP data). Fig.7.2 Time variations of geopotential heights (from TEMP data). Fig.7.3 Fig.7.4 Fig Time variations of tropopause heights. Time variations of tropopause temperatures. Fragments of temperature profiles constructed from TEMP messages and minute data.

9 -6-1. INTRODUCTION Radiosondes are one of the main sources of data on the state of the troposphere and lower stratosphere. The accuracy of radiosonde measurements of temperature'il, pressure and relative humidity and of upper wind observations is of great importance to operational meteorologists. For instance, the accuracy of the observations limits the accuracy of the forecasts obtained from numerical weather prediction models. In addition, the systematic bias.between observations by different radiosonde types must be identified if optimum progress in scientific studies of atmosphere remote sounding techniques anq also of long term changes in the climate of the troposphere and stratosphere is to be obtained. Laboratory tests and flight tests using specialised reference equipment reveal many of the perfomance characteristics of radiosodes. However, these tests do not always identify all the typical errors in actual operational observations. For instance, operational software of the radiosonde ground $YStem often differs from that used in specialised tests. Methods of -observation in. operational measurements often differ from those used in specialized tests. In the laboratory, it is difficult to simulate fully the conditions experienced by a radiosonde sensor in operational flight, e.g. with respect to the infra-red radiation environment. Thus, the current series of the WMO International Radiosonde Comparison were initiated in 1984 with the purpose of producing direct comparisons between observations from operational radiosonde systems flown under operational conditions. The results obtained are directly relevant to a limited set of flight conditions (e.g. nighttime, daytime with certain solar elevations). However, they may be used to verify the results from other types of tests and may also be used to check the adequacy of operational quality evaluation techniques [11 ]. Phases I and II were performed in the United Kingdom and USA in 1984 and 1985 respectively. As many as five operational radiosondes types were flown in simultaneuos operation, suspended about 40 m below a single balloon. In most cases 20 comparisons flights were made at each nominated flight time. Satisfactory

10 -7- comparison data were obtained between operational radiosondes from Australia, Finland, Federal Republic of Germany, India, United Kingdom and USA. This report presents the results from Phase III of the WMO Radiosonde Comparison. The primary aim of the Phase III was to determine the systematic biases between observations by the most widely used radiosondes in the USSR and China and by the radiosondes used by Finland and USA in Phases I and II. It should be noted that some information about the relative perfomance of the radiosonde systems from Finland and the USSR is available from earlier comparison tests performed in 1984 and 1985 [4,5]. Phase III field work was carried out in August 1989 at the Soviet Aerological Station of Dzhambul of the Kazakh Republic Administration for Hydrometeorology. The station details are as follows: WMO Index Coordinates: 'N, E. The altitude: 652 m. The scheme of the station location is shown in Appendix B. Dzhambul is in the semi-desert region of South Kazakhstan near the Tien Shan mountains. In August mean air surface temperature is 22.6 C, absolute maximum temperature is 42 C (1979, 1984), absolute minimum temperature is 1 C (1942), mean value of precipitation is 5 mm and mean maximum is 49 mm (1895). The precipitation is very rare during this period. The predominant winds are west and south-west.

11 -8-2. RADIOSONDES AND SYSTEMS USED IN PHASE III The radiosonde systems compared in Phase III were submitted by the USSR, China, Finland, USA and United Kingdom. Both, the USSR and China, supplied two types of radiosondes. This allowed the radiosondes in widespread operational use for more than 5 years and also more recently developed radiosondes to be compared. The characteristics of all the radiosondes and ground systems can be found in Table 2.1. Photographs of the radiosondes are included in Appendix A. The radiosondes flown in Dzhambul represented the instruments in use at more than 90 percent of the upper air stations on the Global Observing System USSR systems Two main systems are used in the upper air network of the USSR. The MARS (MRS) radiosonde is flown with -the Meteorite secondary radar ground system. This radiosonde was first introduced into operational use in At some Meteorite-2 stations automatic data processing has been provided by the OKTAVA system. This has been installed at 40 stations since 1988 and was used in Dzhambul. The MRZ radiosonde is used with the AVK-1 secondary radar system. Operations commerced in 1986 and the AVK-1 was in use at 102 stations by the end of Meteorite-2 - MARS-2-2 (MRS) system The MARS-2-2 radiosonde senses temperature using a white painted rod thermistor of approximate length 10 mm and diameter 1 mm. The connecting wires to the thermistor are formed into a rectangular framework and this framework attached to the end of a plastic support. As a result the temperature sensor is hold about 200 mm to the side of the main radiosonde body. Laboratory testing indicates that the time constant of response of the thermistor at normal ascent rates (from 5 to 6 m s- 1 ) shortly after launch is about 7 seconds. Specialised flight test comparisons with a fast

12 LIST OF PARTICIPATING RADIOSONDES Table 2.1 Country Name of Type of Frequency Sensors Wind find. Processing Radiation Weight UA system radiosonde MHz temp. rel.humidity pressure equipment correct. (g) USSR Meteorit-2 MARS ±8 thermistor goldbeater's no secondary automatic yes 300 (MRS) skin radar AVK-1 MRZ-3A 1782±8 thermistor goldbeater's no secondary fully automated yes 300 (MRZ) skin radar (semi-autom. for minute datal CHINA Type-701 SMA-TC-1 400±4 thermistor hygristor no secondary fully automated yes 300 (SMT) radar Type-701 SMA-GZZ 400±4 bimetal goldbeater's aneroid secondary semi automated yes 800 (SMG) skin capsule radar FINLAND DigiCORA RS80-15N 403 ceramic humicap aneroid Omega fully automated yes 210 (FIN) ( ) chip capsule I t..o I USA VIZ= rod carbon aneroid - manual strip no 1000 (USA) thermistor hygristor capsule chart with PC reduction U.K. AIR-3A-RT IS-4A 1680 rod carbon aneroid radio fully automated no 200 (AIR) thermistor hygristor capsule theodolite www 5300)

13 -10- Table 2.2 Sensors of radiosondes tued in Phase III Radiosondes Temperature sentor Type Diameter, ID Accuracy, c Time constants, sec Type Humidity sensor Accuracy, XRH Time- constants, sec J!RS l!rz ~ Rod thermistor I Bi.metall Gold beater skin to SH'l' Rod thel'llis tor carbon hygr is tor FIN Bead thei'iiocap Hwlicap 2 1 USA AIR Rod thermistor U carbon nygrfstor Notes: 1. This information Yas presented by the participants. 2. Time constans are at surface. 1 thicknm

14 -11- response platinum resistance thermometer showed that this time constant of response increased to about 50 seconds at 10 hpa for normal ascent rates [10]. The relative humidity sensor uses goldbeater's skin (tambour-shaped). The goldbeater's skin is linked by a mechanical coupling to a rheostat. The sensor is mounted on top of the radiosonde and is protected from rainfall by a cardboard cover. There is no pressure sensor, since the Meteorite system computes pressure from its radar height measurements (see Appendix F) and the radiosonde temperature and relative humidity observations. The MARS radiosonde electronics comprise an electronic commutator (multiplexer), a "resistance-frequency" measuring transformer and a super-regenerative transponder on a frequency of 1782 MHz. The multiplexer cycle takes about 100 s and is divided into 4 equal periods. Temperature is sensed for two periods during the cycle, relative humidity and a reference signal for one period each. The temperature and relative humidity measurements are checked in an external screen prior to launch. The sensors are used if the temperature difference from the screen temperature is less than ±1.5 0 and the relative humidity difference is less than ±20 percent. The ground check measurement is not used to modify the calibration employed in the operational observation. The Meteorite-2 secondary radar operates at a carrier frequency of 1782 MHz. This frequency falls outside the band MHz assigned for meteorological observations by the International Telecommunications Union. There are historical reasons for the use of 1782 MHz in the USSR, but in future secondary radar developments a frequency in the allocated band will be used. Slant range is measured from the time lapse between the radar pulse transmission and the response from the radiosonde. transponder. Computations of operational observations are made from the raw data on the print from the radar. On this print radiosonde position coordinates are printed at 30 s intervals and radiosonde telemetry data at 5 s intervals. In Dzhambul, the computation were automated using the OKTAVA system. In this case the radar output was transformed into digital code by the OKA-5 device and then

15 -12- transmitted through a RS-232C serial interface into an IBM-type PC. Winds are computed using the following averaging intervals : 30 seconds up to 3 minutes into flight, 60 seconds up to 10 minutes into flight, 120 seconds up to 40 minutes into flight and 240 seconds for the remainder of the flight. Height observations are smoothed with 5 samples used to compute the average value reported in the TEMP message. The PC system used with OKTAVA allows TEMP and PILOT messages to be generated and provides a hardcopy of the observation results AVK-1-MRZ-3A (MRZ) system The MRZ-3A radiosonde uses the same temperature sensor as the MARS radiosonde. However, in the MRZ the plastic support is shorter and the temperature sensor is located about 100 mm to the side of the main radiosonde body. The relative humidity sensor is similar to that of the MARS radiosonde but the sensor is protected from rain by an aluminium cover. It is located on top of the radiosonde. Pressure observations are computed in a similar manner to that in the Meteorite system. The MRZ radiosondes are built using more modern electronics than the MARS radiosonde. The carrier frequency is frequency modulated. The duration of the commutator cycle is much shorter than in the MARS and usually is either 21 or 27 seconds. The AVK-1 secondary radar uses the same principles of operation as the Meteorite-2 radar, but the equipment is constructed from modern radio and other electronic components. The processing of radiosonde telemetry data by the AVK system is fully automatic. This is achieved using an A-15 micro-computer with the software stored in ROM memory. In contrast to the Meteorite system, wind observations are calculated with an averaging period of 1 minute. In operational use the AVK system can output TEMP messages without operator intervention following launch as long as the upper wind conditions are such that the AVK radar tracking is expected to be reliable. In other conditions, the operator must monitor and sometimes correct the radar tracking.

16 -13- A hardcopy printout with values of slant range, vertical angle, azimuth, height, temperature and relative humidity may be also generated in a special working regime of AVK. The possible intervals of data are of 30 or 60 seconds during flight. The positional coordinates on the printout are accurately timed, but the timing of the temperature and relative humidity observations is determined by the radiosonde commutator cycle and may differ from the printed time by at least 20 seconds. As the AVK software is in ROM it was not feasible to modify the operational software to produce the exactly timed temperature and relative humidity samples requested for the comparison. Thus in Dzhambul, the AVK data for Phase III were computed from the hardcopy printout of the AVK-1 ground equipment. The PC software applied similar corrections to those used in the operational system, e.g. the same radiation corrections for temperature, the same refractive index and earth curvature corrections for height, but the temperature and relative himidity samples were determined exactly at minute intervals through the flight by linear interpolation between the data samples available from the printout Chinese systems SMA-GZZ (SMG) The SMA-GZZ radiosonde has been used at most of the operational radiosonde stations in China for many years. Temperature is sensed with a thin bimetal spiral (0.2 mm thick). The sensor is mounted on a vertical duct at one side at the radiosonde body. It has been shown that the time constant of response of the sensor, at normal rates of ascent, shortly after launch. is about 5 s The relative humidity sensor uses goldbeater's skin of similar size and shape to that of the MARS and MRZ radiosondes. The goldbeater's skin is held vertically in a duct to one side of the radiosonde, whereas on the Soviet radiosondes the skin is held horizontally on the top of the radiosonde. Pressure is sensed using dual aneroid capsules manufactured from phosphor bronze. The calibration of the sensors is revised

17 -14-- after delivery from the factory using the results from tests in a pressure calibration chamber at the upper-air station. This revision procedure was performed on site in Dzhambul. All the sensors have mechanical linkages to a rotating drum encoding device. Morse coded signals are transmitted to the ground. type of radiosonde design was used in the Soviet A-22 This radiosonde and in the Graw M60 radiosonde tested in Phase II. In China radiosonde is ground checked in an external screen prior to launch and the sensor calibration curves are altered using the results. In Dzhambul this calibration was performed indoors. The radiosonde is tracked using a type 701 secondary radar which operates at 403 MHz. To avoid the interference with the Finnish system, a separate transponder suspended 20 m below the balloon was used for wind measurements. The antenna of this radar consists of a Yagi array with 16 elements. The specification for the radar indicates an accuracy for slant range of m and 0 an accuracy for azimuth and elevation angles of The minimum elevation for satisfactory tracking is controlled by flights. two 0 observations is 8. operators during The Morse coded signals are received at the ground the Antenna operational station and then processed by a semi-automatic method. The raw data are input manually into a computer and then processed using software developed by SMA. Wind observations were computed using averaging periods similar to those in the Soviet Meteorite-2 radar system. Wind observations were submitted for the first 32 flights in Dzhambul. Starting with flight 33 a fault in the secondary radar developed and any further wind observations by China were always with SMT radiosonde. associated 2.2.ZSMA-TC-1 (SMT) The SMA-TC-1 radiosonde brought to Dzhambul by the Chinese team was not yet ready for full operational production. Some stations use this radiosonde in China, but no observations have been issued into the GTS from this equipment. The SMT temperature sensor is a white painted rod thermistor, length 10 mm, diameter less than 0.5 mm, held at the end of a long

18 -15- length of connecting wire at one side of the radiosonde. The time constant of response of the sensor is less than 2 s at a rate of ascent of 7 m s- 1 shortly after launch and is about 12 s at a height of 30 km. Relative humidity is measured by a carbon hygristor manufactured in China and mounted on a vertical duct at one side of the radiosonde. In Dzhambul, the SMA-TC-1 did not use a pressure sensor. Pressure was computed from slant ranges and elevation angles measured by secondary radar together with the radiosonde temperature and relative humidity measurements. The SMT radiosonde was designed for use with the type 701 secondary radar and a type 701-TC ground system using a PC computer. The software used with this system allowed fully automated processing. The number of flights with the SMT radiosonde in Dzhambul was smaller than originally intended. This was primarily because the system would not operate in a satisfactory manner if the Vaisala RS80 radiosondes was operating at the same level on the flight rig (even if operating frequences were offset by 10 MHz). As observation~ from the Vaisala radiosonde were essential to link the Phase III observations to Phase I and II observations the Vaisala radiosondes could not be omitted from many flights, so in most occasions SMG obsevations were substituted for planned SMT observations Finland system (link radiosonde to Phases I and II) In Dzhambul, the Vaisala RS80-15N radiosonde was used with DigiCORA ground equipment. The DigiCORA MW 11 Automatic Rawinsonde set is a dedicated ground system for use with Vaisala radiosondes. It has replaced the MicroCORA ground system used in Phases I and II. The electronics uses more modern processors and electronic displays than MicroCORA. Software has been revised or improved in some areas, but main processing has been shown to be similar to that of MicroCORA. The software system incorporates automatic control of data quality. The RS80-15N containes the following sensors: pressure - capacitive aneroid with measuring range 1060 to 3 hpa, resolution of 0.1 hpa; temperature - capacitive bead with measuring range +60 C.to 0

19 C, resolution of 0.1 C; humidity - HUMICAP thin film capacitor with measuring range 0 to 100 % RH, resolution of 1 % A difference in temperature measurements compared to previous phases can be expected because of the revised daytime corrections associated with the "1986" correction scheme now by DigiCORA. The RS80-15N radiosondes have the temperature used capability to retransmit navigational aid signals received from Omega and Sigma stations to DigiCORA. Wind speed and direction are then computed from these signals by DigiCORA, using an averaging period of about 4 throughout the flight. minutes 2.4. USA system (link radiosonde to Phases I and II) The VIZ 1392 radiosondes flown in Dzhambul were from the same set of radiosondes used for the VIZ flights in Phases I and II. The radiosondes had been stored in the USA for five years prior to use in Dzhambul. The VIZ 1392 is not currently used-in operational observations in the USA. The manually operated ground equipment used in Dzhambul is much more difficult to operate than the automated ground system used at upper-air stations in the USA. The equipment used in Dzhambul was chosen to provide the best link reference back to the equipment used in Phases I and II. VIZ Corporation manufactures the majority of the radiosondes used operationally in the USA, and the current radiosonde design has the same temperature sensor as the VIZ 1392, the same relative humidity sensor (but mounted in a different duct) and a pressure sensor with similar calibration characterictics to the VIZ 1392 but different orientation within the radiosonde and modifications to the referencing used in the switching sequence. A detailed comparison of the more modern VIZ radiosonde types can be found in [ 12]. The VIZ 1392 radiosonde uses a white coated rod thermistor of length 25 mm and diameter 1 mm. This is suspended by thin connecting leads on outrigger. The outrigger holds the thermistor about 170 mm to one side of the radiosonde body at a level above the top of the radiosonde. The relative humidity sensor used is a

20 -17- carbon hygristor, i.e. a small plate covered by hygroscopic carbon powder. The resistance of the plate changes as the relative humidity varies. The sensor is mounted within a horizontally oriented duct on the top of the radiosonde body. Pressure is sensed using a Nispan-C aneroid capsule. There is no direct readout of pressure from the radiosonde, but a baroswitch' system is used, i.e. mechanical linkage to the ca-psule operates a switch which controls whether information from the temperature or relative humidity sensors, or reference signals, are transmitted to the ground equipment. The operation of the baroswitch means that in the troposphere information on temperature and relative humidity is transmitted to the the ground equipment at intervals of about 10 s for T and 5 s for U near the surface (a reference replaces every 5th U sample). At 100 hpa, T is sampled for about 30 s and then a reference for about 15 s. At 10 hpa, T is sampled for about 200 s followed by reference for 90 s. Baroswitch switches alternately at 3 and 7 hpa intervals near the surface, at about 2 hpa intervals at 100 hpa and about hpa intervals at 10 hpa. The ground equipment used in Dzhambul differed from that in Phases I and II since an AIR radiotheodolite was used to receive the radiosonde signals, rather than the GMD radiotheodolite which was too large to transport to Dzhambul in the time available to prepare for the experiment. The revision to the ground system has been thoroughly checked, both prior to shipment, and after the subsequent return to the USA to ensure that data processing was unchanged. The generation of TEMP messages and data sampler from VIZ system was.semi-automatic in Dzhambul. Data samples were extracted from the chart recorder output from the system and then entered into lap-top PC systems to compute all the operational observations. Measurements of wind with AIR represent operational wind observations attempt was made to derive wind radiotheodolite positional coordinates. radiotheodolite do not in the USA and so no observations from the

21 - /fj United Kingdom system The United Kingdom supplied an AIR Intellisonde system for testing at Dzhambul. This system has been purchased to provide operational observations from the British Antarctic Survey, Halley Bay station, beginning in It will replace an Omega Navaid windfinding system that failed to provide satisfactory wind observations, because of poor geometry and quality of the Omega transmissions at the location. The equipment was operated by a joint team from the United Kingdom and representatives from AIR (Atmospheric Instrumentation Research, Inc., Boulder, USA) with the permission of the USA. The temperature sensor used by the AIR Intellisonse IS-4A was the same rod thermistor as that of the USA system. However, it was mounted on outrigger which holds the thermistor about 60 mm to the side of the radiosonde, about midway between the top and bottom. The relative humidity sensor was also the same as that of the USA system, but the duct in which the sensor placed was much smaller than that of the VIZ 1392, although located in position on top of the radiosonde. a similar The pressure sensor was a dual diafragm capacitance type aneroid capsule manufactured by AIR. This provides continuous readout of sensed pressure unlike the USA system. A CMOS microprocessor in each radiosonde sampled and processed the sensor measurements into the digital data stream transmitted from the radiosonde to the ground equipment. This is transmitted to the ground at 1680 MHz. The two phased modulation of the generator by Manchester code minimises errors on signal reception. A Manchester decoder feeds the radiosonde telemetry data into a PC processing system. The AIR-3A-RT radiotheodolite was used to track the radiosondes. This system can track automatically from radiosonde launch in many situations, but in Phase III the tracking was initiated manually. Once in flight, the radiotheodolite tracking and ground system processing is fully automated. The radiosonde information are combined with the azimuth and elevation observations from the radiotheodolite to compute winds and directions. AIR wind averages over 90 s from surface to 5 km, 120 s 7.5 km, 150 sup to 10 km, 180 s to 15 km, 210 s up to

22 -~- 20 km, 240 s for remainder of flight. Generation of TEMP messages was fully automated but displays of the significant level selection on VDU plots of the observed meteorological variables allowed modification of the significant level selections by the operator at Dzhambul. Occasionally, large variations in the main power supply caused the PC system to crash during flight. AIR produced specific software for the Dzhambul test to allow the initiation of the flight from the common timing pulse. Unfortunately this software module had a flaw, which was identified after returning to the UK. This caused the PC operating system to crash if the signal reception from the radiosonde was poor on launch. This often happened because of the large numbers of people close to the flight rig at a launch. When this occured, the PC system could be restarted and satisfactory pressure, temperature and relative humidity observations were obtained for the remainder of the flight. However, the UK team decided that the data gaps near the surface meant that geopotential height and wind observations were not representative of AIR typical perfomances in these flights and information for these variables was not submitted to the comparison data base.

23 FIELD PHASE FULFILMENT The participants installed their equipment and performed some preliminary test flights during the first week in August A signal to synchronize timing of participating systems at the start of each flight was provided. As far as it could be checked, the time divergence between different systems was less than ~1 s during flight. The field observations were carried out during the period from 7 to 26 of August The configuration of the flight rig is shown in the figure of Appendix C. Up to six radiosondes were released in every flight The programme fulfilment The first flight of the Intercomparison was performed at 06 GMT of 7 August. The daily programme included from 4 to 5 flights. Most flights were performed at the standard operational times for the Dzhambul station, but in order to achieve the recommended number of flights in the darkness, two flights were made during the night on several occasions. The numbers, dates and times of flights are shown in Tables 3.1 and 3.2. Because only 44 TOTEX TA 3000 g high altitude ballons were available, the other flights were made with Soviet N 200 balloons. The 10 hpa level was reached in about 83 % of all soundings. 66 flights were made in total. They can be grouped as follows: a) 19 flights in darkness (near local midnight); b) 18 flights during large solar elevation angle (near local midday): c) 29 morning and evening flights, i.e. when the solar angle was from 5 to 20 (00 and 12 GMT). Table 3. 3 indica ~es the numbers of flights with radiosonde observations at 100, 30 and 10 hpa at the different times Comparison procedures Surface observations were produced from the Dzhambul station. Observations by the duty aerologist were delivered to the

24 -21- Table 3.1 The observational programme fulfilment FIN AIR OS! MRZ MRS CHI H H H H ! H H I I I~ ' ~ ~_j 133_~~~~~ ~_t~z~_:_~ am1 I I ' ~_1_~,~-6_!.~_138 i : il 11 I I I I 8 ~ 34 I I " I

25 -22- Table 3.1 ( continuation ) ,, 43 FIN AIR USA MRZ HRS CHI 111 t ' i P. H , ~ Jj l I I I ! For all systems the 1st column contains the dtiration of the launch, min; the 2nd one is the last presspre level, hpa and t.he third - height, m.

26 -23- Table 3.2 Dates, times and sun elevations of flights Bf I f if FlDat FIGHT HSun Hf 1 FlDat FIGHT f6 f2 7 f f7 7 f f f f f8 0 9 f f to to to to 18 -JO H u 6 6f u f f 0 u f8-3t H:! f HSun f8-28 -Jt f f f Jf Rote: angles of the sun elevation are given ior the time 1 hour later a launch moment

27 Table 3.3 Number of participant's :radiosondes used fo:r statistics at constant p:ressu:re levels at the times indicated Times(GMT) Participant Radiosonde (label) (100 hpa I 30 hpa I 10 hpa ) FINLAND (FIN) RS 80-15N /16/13 13/12/11 19/18/13 USA (USA) VIZ...;, /12/11 16/15/12 15/14/12 18/18114 I l'\:) ~ I USSR (MRZ) MRZ - 3A 12/12/ /10 16/15/11 18/17/13 USSR (MRS) MARS-2-2 p/3/3 12/12/8 12/1019 9/9/7 China (CHI) SMA - GZZ 6/6/5-13/12/9 8/8/6 17/17/12 UK (AIR) Ai:r 6/6/5 13/13/10 13/10/7 "'18/17/11

28 -25- participants half an hour before la\xnch so that radiosonde gro\llld checks could be performed. The teams from Finland and USA performed gro\llld checks on the top floor at the Dzhambul station building and used an independent precision aneroid barometer for pressure observations. This barometer had been checked against the Dzhambul station instrument to ensure that ground calibrations were of identical quality for all systems. On most flights five or six radiosonde types were in simultaneous operation. The two Chinese radiosonde types were not flown together. The radiosondes were tied to the flight rig, a cross made from lengths of wood of rectangular cross section (about 20 mm wide). This cross was usually suspended about 30 to 40 m below the balloon, but on occasions the suspension length was increased to 50 m to facilitate launch. With the cooperation of all the participants, it proved possible to launch practically every comparison flight within a 5 minute la\lllch window allowed by the Dzhambul Airport Air Traffic Control. During the comparison flight, each team operated independently in accordance with the respective national operating procedures. The project leader checked the timing synchronization periodically during several flights, and no major discrepances were identified. The operational frequences of the radiosondes operating in the same frequency band (VIZ-AIR, SMG-RSSO, MRS-MRZ) were usually separated by 3-4 MHz (more than 10 for SMT). In some flights interference problems occured between the MRS and MRZ systems. The Chinese SMT radiosonde experienced a large amount of interference from the Vaisala RSSO radiosonde even when operating frequencies were separated by 10 MHz. In the Phases I and II other 403 MHz systems had no problems in operating within 3 MHz of the Vaisala RS Data processing All the participants submitted to the project management the following data for each successful flight: - coded TEMP messages, - standard pressure level data, - simultaneous samples obtained at 1-minute intervals

29 -26- throughout the flight. The TEMP messages were delivered in printed form and the standard pressure level and simultaneous minute data were submitted using floppy disks. Operational problems in Dzhambul hindered the rapid submission of data by some participants. This was undesirable and participants in future comparisons should ensure that data are submitted shortly after the completion of each flight. The validity of data submitted were checked by team leaders following the comparison. The USSR supplied eight diskettes containing all the flight data to the participants for this purpose Evaluation of Comparison Data Sets The comparison data set includes the following numbers of flights: Finland- 61 (FIN), USA- 63 (VIZ), USSR- 63 (MRZ) and 38 (MRS), U.K. -52 (AIR), China- 44 (SMG) and 9 (SMT). In some flights, procedural problems occured that prevent the use of the comparison data in the processed statistics. Flight number Problem 7 No start pulse received, possible time shift 16 Rig broken in launch 20 Rig strings got tangled in launch, rig in wrong position No sta~t pulse ~eceived, possible time shift Rig broken in launch During the later flights of the SMT radiosonde the Finnish sondes were suspended 30 m below the flight rig. At those flights the Finnish system was sta~ted about 5 s after release of the flight rig in order to compensate for the height displacement. The flights concerned were 59, 61, 63, 65 and 66. After completion of field work, the initial data set was edited and reduced to a unified format. This could not be corrected until the error reports from participating teams were received in May Specialized software for visual review and data correction was developed by the USSR as well as software for

30 -27- the statistical analysis of the Phase III data. A summary of this software is included in Appendix D. The reasons for changes_to the initial data set are described below Soviet data Data samples at minute intervals were not directly available from the AVK-MRZ ground system. Team members from the USSR keyed data into the comparison data base. manually, using the printed output from the AVK system computer. However, the time assigned to the temperature and relative humidity observations on this printout was not the actual time at which the sensor was sampled. Thus the data samples, although occasionally correct, were mostly incorrectly timed with timing errors up to s. The data samples were subsequently reprocessed to eliminate the timing errors using additional timing information of the multiplexer cycle of the radiosonde, also available on the AVK printout. Copies of the original AVK flight records had been supplied to Dr. J. Nash, as project coordinator, and corrections derived independently in the United Kingdom confirm that timing shifts have now been effectively eliminated from the MRZ samples. The MRZ wind observations reported in the original data base were also incorrectly timed. The wind reported at a given time was an average for the preceding minute and thus centered 30 s in advance of the data samples from other systems. This timing error has also been eliminated in the final data set. Some parts of the MRZ and MRS data were excluded for technical reasons, e.g. interference between radiosondes, bad reception of the radiosonde signals, uncertain tracking and failures of printer. Rather large data gaps occured in flights 30 and 66, so that data were eliminated from the standard pressure levels files for these flights. Some mistakes in manual input for the MRZ system were identified and rectified. It should be noted that the standard AVK procedure does not control data quality and therefore wrong or doubtful data may be included in operational TEMP messages.

31 Finnish data data. Finland did not request any corrections to their submitted Chinese data The Chinese data were revised for the following reasons: a) Some mistakes occured in the process of data key-in. b) The base-line check of the SMG radiosonde in routine use in China, is performed in an external screen. However the baseline check was performed indoors (in a conditioned working room) in Dzhambul. The base-line corrections for temperature were not made for the original flight data in Dzhambul because it was considered that the baseline check within the room might be unreliable. The average difference between the readings from the temperature calibration curve and the readings from the standard thermometer was about -0.5 degree which is very close to the mean difference between the SMG temperature and the mean temperature of the USA-FIN near the surface. Thus, China requested that the base-line check corrections should be added to the temperature data. c) The correction procedure for solar radiation temperature error used operationally in China uses a fixed correction table. Corrections are selected according to solar elevation and pressure level but the method assumes that the rate of ascent is m s As the rates of ascent in Dzhambul were generally less -1 than 6-7 m s at upper levels, the Chinese team attempted to modify the radiation correction table to take account of the different rates of ascent. The computation in Dzhambul contained an error, so the daytime temperatures and geopotential heights were recalculated in Beijing to eliminate this error. d) The pressure value for the Chinese SMT system was calculated using the range and elevation measured by the secondary radar. In order to reduce radio interference from Finnish sonde, the radio frequency of the SMT system was temporarily adjusted to a frequency about 3 MHz lower than the normal value. This resulted in a significant error in the elevations measured by the radar and thus a large error in the calculated heights and pressures.the Chinese team was unable to revise the computer program in time to add the required correction (+0.3 degree) to elevation values

32 -29- measured by the radar during Phase III. The error was subsequently corrected during reprocessing in Beijing USA data Small corrections for errors introduced by operator errors in data reduction from the ground system chart recorder were applied to a small number of samples UK data (AIR) On those occasions when the AIR ground PC system had restarted following launch, only pressure, temperature relative humidity observations should have been entered into comparison data base. Some geopotential height and wind data eliminated from the original data set for this reason. The elevation angles in comparison flights at Dzhambul to be and the were were often lower than had been predicted prior to the comparison. The AIR radiotheodolite was poorly sited for tracking at the lowest elevations (a site on a flat roof is to be preferred). The UK team decided to eliminate all wind observations when the tracking elevation was less than 20. Thus wind observations were eliminated from parts of 14 comparison flights. The problem of obtaining accurate wind observations at tracking elevations 0 lower than 16 is a typical characteristic of the present AIR radiotheodolite antenna design, and has been demonstrated on many occasions on tests in the USA and United Kingdom Final data set At the invitation of the Central Aerological Observatory of the USSR State Committee for Hydrometeorology, the meeting of team leaders was held in Moscow during the period of October 1-6, Team leaders reviewed their data by means of software developed by the host country. A limited number of data samples were revised and corrected. It was decided at the meeting that no other changes will be made to the final data set.

33 METHOD OF ANALYSIS As ~n previous phases, a multiple regression technique was used for the statistical calculations of the differences between the radiosondes compared. The estimates of systematic biases could be obtained using the mean value (sampled average)... Hi,}:; _!_ A~ k = I (y. -yk ) N. k ~. j =I ~ J J ( 4. 1) of all the levels (points) where the measurements j were received by both radiosondes. But the Dzhambul comparison data base has ' occasional large gaps where systems failed during flight or erroneous observations were obtained. Also at some flight times certain radi6sonde were only flown on a limited number of the possible flights. Therefore the application of the sampled average as the estimate of the systematic biases does not guarantee consistency of the results for the Dzhambul data base. The equation (4.2) "' A;'" = A.. - V [> ~ J 'A. J}; is not satisfied at all levels (subscripts i,j and k can refer to any three different systems under investigation). Due to this fact, noted in [8 J, the regression e.stimation technique which guarantees the consistency is used.

34 -31- The multiple regression technique is described in details, for example in [9]. We shall use it to calculate the random vector where components are the systematic errors of the compared systems. If the result of the measurement of meteorological variable, j, by radiosonde, i, is expressed as the sum of the true value, xj, the systematic, et., and random errors, ~'~ j, i.e. y ~ j = x j + e~ + E; ~ j, (4.3) then the calculation, to find the required values of e~, given independent between e~, requires the weighted sum of the squares of the random deviations to be minimized, as in H M p = l l m~ j w~ E; ~ :) m in I,.j (4.4) ~ = l j = l where wt. - the weighted coefficient which is the inverse of the a priori variance associated with the measurement by radiosonde ~. m~ j = ' 1 - if the data of radiosonde ~ were received for the meteorological variable j; { 0 - if otherwise.

35 The detailed deduction of the equation is contained in the paper [8]. We shall show the final conclusion: m l m~ j j = 1 w;, }I l mkjwk[<ylj-ykj)-(e~~ek)] ~~~ = 0 l'l (4.5) Here, the subscripts k and k refer to the radiosondes types and j - to number of measurement. A system of N equations results but its class does not surpass N-1. The degeneracy of the system is a simple consequence of the fact that the systematic errors of' the radiosondes in the comparison may not be estimated using this model. As the systematic difference of two systems is the difference of their systematic errors we may lower the order of the system by working out the regressive equation in respect to systematic differences. Given the requirement for consistency (4.2) the final equation will have the following form: ( "" "" T A 11 a~ j A I 16). = ( b1 '... b )'l' (4.6) w 1 z ' $ ~.j=1,5 "' Here, the A 1 k is the estimate of systematic differences between system I and others Ck=2,6).

36 -33- w. \ when i. =j-1 ~ = 1 a~ j J (4.7) H l m~ t. m j + 1, ~ L =I 1 otherwise l b. = ~ l m~ ~ mk ~ w k ( Y k ~ - Y j t. ) k = 1 I L = 1 ~ l mkt. wk ); = 1 (4.8) Here M is number of measurements which are the background for estimating systematic biases. means. measurements of meteorological variables, t., by system i. Multipliers mi. L, as earlier, show the presence or absence of data for system i at the point 1. wk are systems weighted coefficients. The equation (4.6) was used for the estimation of systematic biases both for the measurements on the standard pressure levels and for simultaneous samples. For the standard deviations the sampled dispersion was used: 2 N 11 ~ 8i " 1 k 1_. [. = 1 o! k = (4.9) N(N-1)

37 -34- Here 8 1 tl=y 1 L-ykL is the difference between the measurements of two systems at the point l. N is number of points where we have data for both systems. The selection of one of the systems as the reference one (marked by index 1 in equation 4.6) is not critical.the final presentation of results for this Report follows the recommendation of the International Organizing Committee and is made relative to the average of the data from Finland and the USA. Inside each category simultaneous data sets are 'subdivided ~nto 13 pressure bands according to table 5.1 from [7]. However, the boundary between the first two layers was moved to 800 hpa. thus increasing the sample size in the lowest layer (in Dzhambul usual surface pressure was less than, 9412! hpa). The analysis of the standard.pressure levels data.follows the above technique.

38 COMPARISON OF SIMULTANEOUS MEASUREMENTS Statistics have been produced separately for each meteorological variable at each observation time, i.e. night (18 GMT), early morning (00 GMT) with launch shortly after sunrise, midday (06 GMT) and early evening (12 GMT) with solar elevation decreasing as the flight progressed. The results for the various pressure bands are presented as vertical profiles of the consistent differences relative to the average of the observations from the two link radiosondes, those of Finland and the USA. This fonows the practice used in the presentation of the results from Phase I and II of the WMO Radiosonde Comparison [6]. A table to the right of each plot shows the number of samples for each data band used in the computation for each radiosonde type (lower number) and the resultant consistent difference (upper number). The standard deviations of the direct differences between observations by different radiosonde types were also computed. They can be'seen on figures marked by "a". Note: the data band centered at 10 hpa always has smaller sample sizes than the data bands at higher pressures (lower levels), so that consistent differences for this level will have larger errors than at other pressure levels. At the Moscow meeting in November 1990 the team leaders reviewed the systematic biases between the measurements of different radiosonde types. Mean differences in the temperature and pressure observations of Finland and USA in Phase III were larger than in previous phases. The team leaders from Finland and USA reported that radiosonde instruments and data processing in Phase III have been checked and were expected to produce similar quality observations to those used in Phases I and II. Additional AIR and Vaisala comparison data made by Dr. John Nash in 1990 also confirmed the differences. Therefore an additional test data which might help to understand a reason is quite desirable. Nevertheless the team leaders agreed that presentation of results for the Report on Phase III follow recommendation of the International Organizing Committee and should be made relative to the average of the data from Finland and USA.

39 Geopotential height The consistent differences between simultaneous observations of geopotential height by the different types of systems are shown for the four different times in figures 5.1 to 5.4 respectively. At pressure lower than 100 hpa the MRZ observations should have been the most consistent throughout the comparison and may be used to refer between the different observation times. To understand better the sign of difference one should bear in mind that the Finnish radiosonde show larger height values than USA. At most pressure levels, the Finnish geopotential heights had a larger positive bias relative to those of the USA than in Phases I and II. In figure 5.1 representing the night measurements, difference between the USA and Finnish sondes reaches 970 m at the 10 hpa level. At the other times of observations the divergence of heights between FIN and USA is considerably smaller. At the same time one can see that radar ~ystems (MRZ, MRS) and Chinese SMG sonde (CHI) show rather close results. The MRZ and CHI data are particularly alike because the the differences between those radiosondes do not exceed 15 m until the 100 hpa level and reach the values of m only at upper levels of 15 and 10 hpa. Data of all three systems are much nearer to the Finnish sonde. In relation to Finnish sonde their deviations are not. more than 30 m until 100 hpa and not more than 200 m until 20 hpa. The behavior of the MRZ and MRS deviations relative to FIN is rather stable and synchronic and besides their devations are approximately similar at all times. The results between hpa confirm that the AVK-1 radar observations were within the accuracy specification for the Soviet radars. The Meteorit-2 (MRS) geopotential height observations were typically 20 m and higher than the AVK-1 measurements between the surface and 200 hpa and about 40 m higher at pressure less than 100 hpa. (The occasions when MRS and AVK-1 tracking were clearly less than optimum were eliminated from the data set before computing these differences.) The Chinese geopotential height observations were very close to those of the AVK-1 (MRZ) radar between the surface and about 30 hpa (typically within 15 m from the surface to 100 hpa). At levels above 20 hpa there was considerable variation between different data sampj.es, see Figs to 5.4. with a general tendency towards a significant negative bias relative to the MRZ radar observations.

40 The data of AIR radiosonde are worth of a special attention because of the original behavior of the curves. AIR geopotential height observations show a characteristic variation with height relative to the Soviet radar height observations at all observation times. At pressures lower than 320 hpa a substantial negative bias relative to the radar observations developed, with a maximum value of about -100 m at 140 hpa. However, as pressure decreased further the bias reduced to a small positive bias at 32 hpa but at even lower pressures the negative bias increased again to 600 m relative to the radar observations at 10 hpa. The origin of this variation is primarily in the radiosonde pressure sensor measurements. In conclusion, the largest differences between simultaneous geopotential height observations in Phase III were smaller than in Phases I and II. This was because in each of the earlier Phases there was at least one radiosonde type with systematic pressure errors of at least 3 hpa. Estimates of the reproducibility (ls.d) of the geopotential height measurements by the different systems can be found in Table 5.1. Values for the Chinese SMT radiosonde have been included in this table although the sample size available was very much smaller than for the other systems. The reproducibility of the Finnish observations in Table 5.4. is similar to that deduced from the comparison of Finnish observations with measurements by high precision tracking radar at Wallops Island in Phase II [6,7]. The reproducibility of the American observations appears slightly poorer than that found at Wallops Island. The worse reproducibility of the height measurements of both link radiosondes at the lowest pressures in the stratosphere may be a consequence of the random variations in the radiosonde pressure sensor measurements. The reproducibility of the Chinese and AIR observations degrades to a greater extent than the link radiosondes at the lowest pressures. The reproducibility of the MRZ (AVK-1) measurements above 100 hpa must have been of the order shown (certainly) better than 50 m since the standard deviation of the difference between Finland and MRZ was 64 m at 32 hpa). The MRZ values could not be quatified accurately without a more reproducible height reference than was available at Dzhambul. The significant change in the

41 -38- reproducibility of geopotential height measurements between 320 and 100 hpa for both Soviet radars shown in Table 5.1. is explained by the influence of the random tracking errors in radar elevation as the slant range increased from about 15 to 50 km. The reproducibility of the tracking available from the Chinese Type 701 radiotheodolite + transponder was not as good as that from the Soviet radars at Dzhambul, but did appear to be consistent with the equipment specification. In summary, the radiosonde systems of Finland and AIR produced more reproducible geopotential height observations than the secondary radars in the lower troposphere. However, with weak winds in the stratosphere, as at Dzhambul, the radars are able to produce more reproducible height measurements at pressures lower than 100 hpa than the operational radiosondes using pressure sensors. Table 5.1. Received from Phase III estimates of the typical reproducibility of geopotential height measurements at given times into flight. (Estimated from the standard deviations of the differences between simultaneous geopotential height observations for selected data bands). Units: m. Approx. Pressure (hpa) FIN AIR USA MRZ CHI MRS SMT Note: The reproducibility of the radiosonde observations of geopotential height at pressure around 10 hpa is of similar magnitude or larger than the consistent differences found above. Thus, the variation from flight to flight in the heights assigned to temperatures at these pressures is significant for remote sensing studies in the stratosphere.

42 -3:1- P, hpa ' Differences of geopotential Time rf:q~ r.,. l 'IT 1 r -r.. :~r =':_~~l~>- I.. ""="~...I I., : ,K u.:..:t: ~..!t....!.. r?.. :.. I i l! \.,. ;---t----j-~ J i!,/! l :... ii..j... :... : n 'f"!... t-,... :... l.. :! i [\, i i I Y\l /1/ i i !... '!'... :...!.. "t.. :... : ''\''' f!...,.. T'... :...!.... I i i i : \:! \~\:I 50l r r.. r iv... l l! 'l'.!tit... F... i... T l i i i i ~ i M P i i i i l l l\ /l rl\./ l l l 1001'' :... -r... r.. :... /f r r 'fl/f'. -r... r... '1'... :! : :! ~! I i I!!! I j i i i l r i 1/ J i l l ~ r r l r.,. r Jt r r r : -r 'i-.j Jt7.,. r ~.. r \ll rr:.... j... r... :.. I : : ' ' ' 1\ ' ~if 'I : : : 200,. 1 : r ~ :.... r.. r.. ~ I. i. i \!J.~/ i i i 5001'.. :.. 'j'... '''j'... '!... '!''... ''Rf'''f(''!... j... ''!'... '!.... I ' i 1 1 l l ~lb l l i i ,...,...,... ljjffi't!!...,..... i i i I I il I i i l l rija; * - FIN 0 FIN AIR CHI fl( li lu i lu St. us { AIR. V - CHI " - MR.S A - MR.Z MRS MRZ USA tlll lli2 152 lh lllll ss & ( Ill ( A - USA Fig, 5.1 Simultaneous height comparison, nighttime (gpm).

43 -fro- Stand. deviations. Geopotential Tirne 18 P, hpa 10.l l~ 'R/'... : T F... ~1~,;.1:_:~-~~~,;}? ~.r~-~~->r~~)~~~~~r')t l l... I! \ /{\! : : !..,;...-- : 14 r... i' rt-r o,:.. i' 11 : } : \ : : -+- : : : : ::~ {tj~i~j~ t r J t : Ill FIN AIR CHI MRS MRZ USA lJ lll ' lli il.~>r ~ r 1 r r ~ lli ~ i lli0 l::r lrf r J r : r t ~. ~.~(...:...!... i...:...:...!... i... i i JJ ~ ~!!.!!! j 200~fi, r, : r. T r ::: ~i I! I u, I t I t I t I! nr 111.., :... :! : :. : : : 'i'..., r... j... r... j.. ~ 850F... I - FIN Cl 4 * 10 AIR " - CHI MRS u U lu i lib (1) lli lis 70 MRZ A - USA Fig. 5.1a standard deviations.

44 -'-11- Differences of geopotential Time 06 P, hpa FIN AIR CHI MRB MRZ USA A ~:~~~\V I ;~~: ::;: ::::: :::: r r- T r r rv<~-~- ~~~1l T &7. ~ ~ l l \ i l l >~1~ +-1~~>~ 82. I ~ ~ ~ ~ ~ ~ ~ ~ \ I \ 1 \ l 189 1=:0 1..., ~... ~ ~ ~ i,..., ~... i,...,:...\1\11 1 V' rn... ~ 29 1: " : '! l : l : : ~ 1 i 111 1::!::::1:::::: i:::::::r:::::j::::::j::::::r::::j:::~~ l :: 14., I : : : : : : : ij :'-{I ~ 199. :...:... i...:... J 200, : l ;... I l 1 ~~ t :... tj. h r. :;; I : : : i : ~ ~ ~ \~.. 11\J.. r 1! r r r r r i 1Jl r 1:! 320 1=:00, 1...;... \... \... j...) :....) () : : : : : : : : 1; NI f.: : : : : : : : : UtuJ( 1001 i!!!.;..; qj)t 20.! cf.rr.,. r! 12. I : l l l l l l l ljji / l ~ 1!. 1 : u lil lis ~3-1 1 * 10 - FIN c - AIR V - CHI "" - MH.S.. - MH.Z H a- USA ss Fig. 5.2 Simultaneous height comparison, daytime ( gpm l.

45 -42- P, hpa! Stand. deviations. Geopotential Tirne 06 ::~ ~ ~ vr:--:c~:1l-±:-~~ 11 ~ ~ /; 1 ;...---~.i.---::::> -; ; ; i 2011''... -~... ~..,...,...,7~-~~~::p... ~... ;... ~...! ; i/ ; ~:::t"< ~ i ; ; ; 11 i V ~:::.---~ ---k_. i ~ i ::r ~r1~f1~ r. r : ~ f I I I I I l::r i;i~~~ 140 ~-..Jr.:.f!... l.. t... t f..., 200 ~....ll~v. i... L 320r}f 11 \i;}f ~ i i i f ~ ~ ~ + 1 r : I j I i t...!... )... -~...[.. ~-..[ ~-'?{ r)! : ~.... ~ : ~! uiu 11 ~ ' ~ i ~ i l i Ill I If i. i. i i 700ftl x 1 r r 1 r r ; 1 e FIN AIR CHI MRS MRZ USA e. 99 e llli r ll..f i i i = ~~= * 10 1 FIN 0 AIR CHI "' - MRS 459. se l'l ! r.s lis e. 21!9. 341i li e'l & ! lie U:l li ( Ill ll2. 89 lili lib u. ll lll. Ill fill li'1 MRZ A - USA Fig. 5.2a Standard deviations.

46 -43- p' hpa. 10 & r.. Differences of geopotential Time 00,..,,..,,. ~. ---f--... l l i! rv~---..! I i ffi.,,.,..., ~:1, I:1~r;t~IJl< ,...,...,.. :r ,r.,. ~;~ I ~ ~ ~ ~ l ~ l ;---~ ~ \ I i!! i! i 1 i r \ _./ ~ ~ l: l l\!jl\/ 1':0,...,...,...,...,.. <...,. {> <.. J ~ \)! i!! )! I! l,. 1 \\!!! ~!.I! i! \ ! 1! 1..! ?t<.r! r I : : : : : : I : I il : I I!:!: :! :!!:!: I V 11\! /J )',: 1001! : 1! 1! 1 p, ''f'i'' ;. r I \ \ : \ \ l If J 1\ / 140,.. T.. ;... r- r.. r... r... 'frr-r.,-r ; r.. I!! i!!! I \ i I I I i I 2001'...!... f "t... l"...!... -t t;d--'f::,. ; }... I :!!!! l I, \! h' f 320l l! l l l! \ rrf~'r! l...;... i-...;... -j--...;... 4in r I : : : : :! \ :1/ }' I : l ~! ~!! 1.! / f I! I ~! i : l! f:l.l I ~ 100,... : r... r..... T... r... r... rrt "'.. T I. ~. ~. ~ \..\.\ i' '.\ I.:.5-3 c - AIR FIN AIR CHI MRB MRZ USA u ! u. ' Ill * FIN V - CHI "' - MRS u 1. -'1' ts 119..( ( (2-3.( IL (.( us t. lb ' & u Ull. 71. li ( li ! t ( (8 u 92 8.( i MRZ A - USA Fig, 5.3 Simultaneous height comparison, morning time (gpm}.

47 -41;-- Stand. deviations. Geopotential Time 00 P, hpa FIN AIR CHI MRS MRZ USA.i 10 ~ r : r 1;.~'" i r J-~~:-r-,;?~~~~t~ IL ! ! l2 ( ( ~:l txttmfn r r l 32 r... ~t..,... 'F ;...v,.. ~.!.. ~ ~ ~! t ~ 1 11 ~I f ;!i,../ : ~..., i... : i ~ : ~ ~ : 50 ~ ~t1 j : l j! i t j 70r.. l"rlf\j... r.. T.. T... r.. r... r... i... r.. r r.. 11 :.1111 \ : ~ : : ~ : : : ~ ~ 10011'... H ~ ~r.. ~....!...!.. r... ~ !.... t.... : f I t l: 1 ~ : : : : : : : : : 140 r rv: l i!... : J :... i j J 200 ~. IYlT !'... r... i... r.. r... T... i... i..... r... T t ~f \! -l- l l f -l- l!! -l- l ll/ ~1: ; ; : J ~ : : : : : : : : : : : ; 500 rrmn : : r 1 1 : r r 1 r r ~ :...!....:... r r.:.. : 1 850j' * 10 FIN Cl - AIR T? - CHI T - MRS ' '18 ll u l. 2& '1 6's (8 87.!Ill 18..u li UJS ' Sl ss. 85 ss S lli '1' 44 MRZ A - USA Fig. 5.3a Standard deviations.

48 -45- Differences of geopotential Time 12 P, hpa FIN AIR CHI MRB MRZ USA! 10 r-~~~~.:.l.. r... us us (0 li r _1;;:r~ \ i ;~;.. r... -r? 141! j l ~r~~"tc-t~. ~~tt: :...!... :...! !V.:...:.. 'l"'tl'-:_:.!.. r.. -~,.-..!..... ; ~ ; ~ ~ ; ~ -----~R. -.i... _ ~~ V ~ I 1 I 1 I l>"l11~\l 50H... r...!... l... l... r...:... r... -r r Krr... I' : : : ' ' ' : : I l' \11 I' 70 'f r.,. r.,. r.,. r.,. ill' l ~.. : :!.. r..! :! :..! fi' 1 'r r r \ \ \ \ \ \ \ : 1 \ \ 1~ \ h 1401[... l...;...!...!...(... l...!.....j.. t9 i...,.t-it.. I' ' ' : : ' : ' ' \I: lff '' 200 [ ,... -j.... i J i l l +~.!--~ -f : : : : i i : : : \ \/1u: 320,...,...,...,...,... -t.. = rfr f j I L I j i L I \~H 7001: j i < : ; i j : ~f i 8501l f'. ; ~8 ~6 ~4-2 0 * 10 0 FIN - AIR V - CHI MRS lf/ DS (8. DB & ( ( ( ( ( ( -u. 57 -BD ) 82. 8'1 lll. lid & - -.( lf/11. 7l ' u. ' (. l.t. -u ( 184 & u ( ( llll5.u ( J ' /IJ Ill 1.(2 18/IJ 182 ' /IJ ' (0 lil 54 MRZ "' - USA Fig, 5. 4 Simultaneous height comparison, evening time Cgpml.

49 Stand. deviations. Geopotential Time 12 P, hpa FIN AIR. CH I t-1ri3 HRZ UBA ~:) Y.d;-~z. f ~-t=~f 20 r I r /?' 1 ~./ r..... L~~-~>r r.... t..... r ::twvlr;r~] t. J i r rr, ~, A,.,,,,,, If J \ Jl!i! i i i i i l:uuvr r r r 1 r r ft I [ I 'I : : : : : : : ~=I~ I r! l I r T 32011' Mf f..... i.....!.... -~... ).....!... -~......!.. n!jit i /H i i i. i i : i 500 r;-... \. - ; l - -~ \.. \ -~ 7001~-~ l...:... i...!....!.... i...! -~ 850 ~l t t l t l i. ; t. I FIN 0 - AIR CHI "' - MRS.._ - MRZ ' n I lib 86 '18 98 u I ' '1 97 1!1. 2'1. '18. ' ' us I. SI U'J ! '1 97 e Ill ' li 48 * USA Fig. 5.4a Standard deviations.

50 -4~ 5.2 Pressure The pressures reported by the two Soviet systems were computed from radar geopotential height measurements plus the radiosonde temperature and relative humidity observations from the surface to the level considered, see Appendix F. In the other systems pressures were sensed directly using aneroid capsules of various designs. The consistent differences between pressure observations for the four flight times in Phase III are presented in Figs to 5.8. At nearly all levels there is a small variation with launch time in the systematic bias between pressure observations. An exception is found in the data bands centred at 850 and 700 hpa. At 08 and 12 GMT the USA pressure observations were 1.8 hpa higher relative to the other systems than at 18 and 00 GMT. These differences were not present to a significant extent in data bands at lower pressures. This day-night difference in USA observations was not observed in Phases I and II. It should be noted that in previous two phases the differences between link radiosondes did not exceed hpa and variation from Phase I to Phase II was not more than 0.5 hpa. And for all that in Phase III the dispersion of pressure differences USA-FIN happened to be in the range of 0.5 hpa. An additional comparison test was performed at Wallops Island in spring VIZ 1392 radiosondes similar to those in Phase III were flown using the ground system from Phase III. Vaisala and AIR radiosondes were also flown with similar ground equipment to that used in Dzhambul. This test will be designated SITE-4 in future publications, but some preliminary results may be mentioned in this Report. At pressures lower than or equal to 320 hpa the differences between USA and Finland in SITE-4 were similar to those found in Phase III. Therefore, the positive bias between USA and Finland in Dzhambul at these pressures did not originate from operator error or errors in test procedure, or because of specific flight conditions in Dzhambul. At 700 hpa SITE-4 and Phase III results disagree. Thus, pressure errors occured at pressures of 700 hpa and higher in Dzhambul which have not been observed in the other tests considered here. The radar systems (MRZ, MRS) where pressure is derived by the

51 -48- static equation from direct height measurements and SMG sonde show approximately identical results: considerable decreasing of 3-4 hpa at the lower levels hpa which corresponds to larger discrepancy of height measurements up to m. Further to higher levels the pressure values become uniformally more close to values of other systems. And already from the hpa levels the differences decrease in most cases up to hpa. The exceptions are the MRS sonde with bad statistics in the morning (fig.5.7) and SMT sonde also at 00 GMT (the same figure). The last one shows the differences of 0.9 hpa at the levels 15 and 10 hpa. Finally, it may be concluded that the radar systems, especially the most reliable MRZ, provide rather acceptable estimates of a pressure when measurements of height and temperature are also good. The AIR pressure sensor observations had a more complex variation with height than the other pressure sensors in Phase III. Figs to 5.8. demonstrate that the AIR observations were generally close to those of Finland between the surface and 320 hpa but at 200 and 140 hpa the observations were higher than Finnish observations by 1.6 hpa. The positive bias relative to Finland decreased at pressures lower than 100 hpa until AIR pressures were very close to those of Finland between hpa. As pressure decreased again the positive bias relative to Finland increased to about 0.9 hpa at 10 hpa. Similar variation in the vertical relative to Finland was also found in subsequent SITE-4 and UK tests. The variation in calibration in the vertical is primarily the consequence of errors introduced by the conversion from engineering units to pressure by the CMOS microprocessor in the radiosonde. The polynomial used in this processing was not of sufficiently high order to fit the sensor calibration to better than + -1 hpa accuracy. In a subsequent AIR radiosonde design where the conversion to pressure is performed by the ground stat.ion software the difference from Finnish measurements at 10 hpa was similar to that in Phase III but it did not change significantly between 100 and 10 hpa. Table 5.2. contains estimates of the typical reproducubility of pressure observations deduced from the Dzha.mbul data set. and

52 -49- Table 5.2. Estimates of the reproducibility of pressure observations in Phase III of the WMO Radiosonde Comparison, derived from the standard deviations of the direct differences different systems in Phase III. Units: hpa. between Layer FIN AIR USA MRZ CHI MRS the Near the surface the reproducibility of the AIR and Finnish radiosonde pressure observations was clearly better than the other systems. Whilst the reproducibility of Finnish pressure observations was similar throughout the flight, the AIR pressures were less reproducible at lower pressures. The variation of the reproducibility of USA pressure observations with height is typical of that obtained with current operational radiosondes in the USA, see [12]. The Soviet systems have relative poor reproducibility of pressure observations close to the surface, but at the lowest pressures the MRZ observations were expected to be the most reproducible of all the systems.

53 -50- Differences of pressure Time 18 P, hpa J. 10r -:- -:- r -1 : \r n _./f.r : 14li... :... L...:...(... i 1 -~ Ll:.. J...:... r '. /1 t-r! ' 1 1 _.. "t " ; -~-.,. ~- : l T.r -rr l : I' : / /l v: I : 32 1r-... r -~ -. r _... >( v.. >/.,.... t\ r 50 IC r T : r "Ll. :.:l1:... l. 1"\; : 70 tl...(...!-'... t... j... '!'f. -~J; <iii >b;<.:... '... j. -~...:... r ~ = ~ ~ il ~ l ~ ~{_ ~ \ ~ 1001:--... j...:... :... b~~::r... y!f.. [... -~- : :--:q~-l- ~~-~-.. ~~ ~ ~ ~ ----~-- \._ ~ / V ~ ~ ~. -~--... \._~ 140lr r l r /' r r: -~r-,~ - l... r r r.t 200 t, : fkj;' 9 l ' -~r:-j:'"~r r -J~~;:~J~~~~?~~- 1 1 :\>> r l 1 )t 500 r ~- ;l!"'l!:. ly f ; 1 a.:~~~- -~ -~- ~-.t:- ~- IL- _,... ~---~-:;~-~-- :. l r~-\--._l. l : / l 700 r~~:st~2ji~~cr]_. <t~::-t... Jl...,... FIN.AIR CH I -.s SB -.11 llili s lsl -.7 U : :0.-'f' n,~>-a ;_: jil -.1 li : i5.:..5 5 * 10- J. - FIN c - AIR " - CHI,.. - MRS li ss lli U li us l:l !iS l.t li li St i l li 50 t-1rb MRZ UBA.._ - MRZ A - USA li B Fig. 5.5 Simultaneous pressure comparison, nighttime (hpal.

54 -51- Stand. deviations. Pressure Time 18 P, hpa 101!' i.. \.. -t"~ -~ r -<: ~ -~ ~ ~ \ I\: : I \ ' : : : : ll \! \) i./ \ i i i i i 14 ~-- ~\~J<~~\- ;r - r /l --- 1! r 20 r v< \:v T : -~ - r ; r it i,i\ \\i l ~ j ~ l i 3 2,... ~< T;_:_ r;;~... T. <... ~...,...!... ~.... rl, ' -~\' \,,,,, l! ' -.., "f\... \ :. :. : 50 ~.. :.. r-ti~lr..... :..... r....:.. :- 11 : /~V.1-r~----: : : ~ 10 rr t...?1'i\ 1.. ~....c<:... r r p : I : I\! :,---- : 11 i I i I \,1 i i ~--~--- :. 10@!r"... '"f... 'If' ~ T.:~j..,...!... ~...,... ~ i I i f\ ~j i :. 140 ~ 'i1"... ~.-;.r )"Tl... -: :- 200 il...,... '"\{..,... i:~;~c:~>y... 1 l1 ' I ' \ ' " I ' ' ' '... [... <. FIN AIR CHI Sf.l ss lll U l.lil "' UC:l t-irs HRZ USA s & B ! !! i :::~ > l 10ii~+<, r 700 ~... i.../~.. j...)... > ~ l.> ;~-~f"t.:._:~>~<... i...' il.../ ~ \ ~ ~-~~ ~-_:~ i 11 / \ r... : -,:::---_. 850 '!',~&~ I ' ' * :10-~ l41i 1: "' Ill FIN Cl - AIR CHI,.. - MRS I& - MRZ l.li U lil lli 6C:l 70 a- USA Fig. 5.5a Standard deviations.

55 -52- Differences of pressure Time 06 P, hpa A 101 r r r :- -r ----,.-:-,.-rv : - - ' : : : : : I : I 1,~1 : 141..:... -~... -~...:...:... -~.:. }4+...:... I :. ' : : I '1P. I I : I :.. : :!/ill I : 201 ; -.. -~.... :.. r :-.... r:-rr;r :.. - : : : -'' :J" V 1 ~. ~ /f ~ 1.A ~ 3 z -.. ~....:......,....,....,... 9r ~'Yr'.., : : : ltll,t:\1, : l : ; tl,i ; ~ j : 501" -~... :... :... -~... :... -~ :-,;r.:r...,.... I : r.,\y/ I. I : : : l"fl \ : 701'. -:......;... >.... -~ :... iftt"i ''f... :. I~ : ~,1/.. -~,...._'t l.. : :..., IF :\ ' -\. ~..., : j.._.. LR_...,. : : : /i-- - : \ \ : I l ~ ~-~--17 ~ \\! r : ,.-..,...,~::..:~~r...:... -.:xr : :-.. _J~~;:~>~r 1... ~)>~~0.. 4~-.: ". ~...:...'.. ~~:.l;.t :~-~~=;:~>~~ lk<<...: :. >,\ I : ~---~-:~:::~ ~? :...=:~---- :..._:... :--:~-_:.._, '"~~--...: "-.r,:<- \ " ~-~-.. ~.,... - I ; -...\ _ ----t\ i '\:~\. / ::J~=--~~'"'rJ=_/_>=-Pf I \ ;., ~{, FIN' AIR CHI fl 71 D2 li ! li !i li ls!i ' l.li L FIN Cl AIR CHI "~' - MRS.._ - MRZ MR.S HR.Z D2.4.2 ll4 94. s Ill.Ill 97 Hl Hl !ill S.li ne b. - USA USA Bill s il Fig. 5.6 Simultaneous pressure comparison, daytime lhpai.

56 -53- Stand. deviations, Pressure Time 06 P, hpa FIN AIR CHI M.RS MRZ USA 10 rr lrr r r r r r r r r 11 lw\ i I!!!!! i 14,.,,. r,~; r r r r r r r r I i'\ ~ i I 1 i i i i i 20 rr r nr<<r r r r r r r r 32 rr... ~J \-<f>t. "!-.. -!-... "!-... :... l... l... n v.., 'k i 1, ~ : ; ; ; : 50[... ~....l,\ rr\"; \ 1 r r r r r r :\ : I,: : : : : : I!1, 1 i I \ \. i 1 : 1 : 701 rr r r r r r r~;~j~~~~~i r~\ I, \, 1<::---' I,,,,,, 100 fib... ;... "f 1. 'ljl'f' }. T.:_:.. :... :... :... :... ;...,,. i '.,! i/ /1,,1! :! i I! liv/i 't, i!!! 140 r... r.. t('<~.:.r.. rr r... r... r.... r ~... ~...(.. ~,~~ :f,...{... j......j... j... ~ ~ ~~-~. ---r\(.. \\ ~ \ i i :! 3201P'... ;... ;... p.a.-~~ :. 'l'.. '1'... :... '1'... : '. \... +-~"' ~ L 1 l ~ \\ \ ~ I ---r---r----~---j ~::r tji r 1:~~-l-A~ 850 ~~ ~.- FIN [J - AIR V - CHI 'I' - MRS I! e ' * 10-l ( I! li I) Uli i lis l.s ( ( MRZ i>. - USA Fig. 5.6a Standard deviations.

57 -54-- Differences of pressure Time 00 P, hpa FIN AIR CHI MRS MRZ USA.i 10,. r : r :....:. : i::,:::::::::,:,::::: :::rl.~~~~,,_!i;_._,p~;;~--,,, : : : : 14j"i"... )... t... :... T~-: -.. '~0,!. ). -~ -~ ; L.:.>~~]~hv<f.._[,,_:_:::::: ! ; 0 1 :21! I,,, {1 ifr1+ ~,, I ' ' ' I,.,!1 I u11 I' ' ) / 11! I : : 501"!' r.... t... ~.... J_.>s~:;r ;,?-:-.. 4<... '!'..... :.. I ~ ~ : ~.. / ~-\// i \! ~ :.. :.... -~ -~/1"'.:.:-~"".. : _.P;r.. :... <tj : I!! :.-t~+----~---: /{/ t.\, ; :.... :.. :.. ;.f -~ :.,..,.";<.. : Q< : <t r i!! <- I!! I! --~--+ -~-~~:~ -.J \,. 1401'... :_:.J~::::~:~-)~-: :... J.-~-:..:~ '1'... _:,)~-~--~,~--:.~--~.:.t_~ i"! "\:"',f" ""'f"""' f''"ll!.''!"""':'"'"'.:>-~:.:..:..:~:..:.'f""f'/ ' -1.2! : \ / : ' \ : J~---=~ : :./ J.-~~,.:/ " <..::.~-.:.._..,... _l'>'1~... 'jk~..:....,...,... -r ~~X! ~ --~~--::::.::-r ~ ~ v,/> ( ~;sill 500 r<:.. : _.7 ~ r r ~?--<"I!{:..,. :-..~'-.. :. -.s :::r I r : : /!! - ---<h y1 :,l :;: 94 '~~;-~r I : : u ~5 5 * FIN C! - AIR CHI " - MRS (8 -A u.1.( lhl a-.Ill Ill.1 4ll s ( ( B B l!i Ill MRZ ;;, - USA Fig. 5.7 Simultaneous pressure comparison, morning time (hpa}.

58 -55- P, hpa A 10 w.:..~~1 t~z1 Stand. deviations. Pressure Time 00.. l >p.. r... r..... r.... -:-... r 11 r--.t--_v i i i i i 14 rr. 'lr 1'\'' 71' r... :... r... -r... : \ \/ I \ \ \ \ \ 20 fll""'t'+ < t.. '9'""...,...,...,...,..., r--~t-~ I I l I \ l 32 w.c:~ rj" ' rr.;...!"... l... t.. -:-... t... I! \~--...:\',!\ j i : j j 1':0,... "A:..i.:_" ,'''?'...,...!"'... ~... :...!'.... ;;70 ~~~... 1.~~~~-\~~:~->L... l l ::~ r 200 ~...! l... : '1\ '\ \. : ;_ ; : : : t:''\., \ : : : : : NU r I=T-~~:~~... >J~~<~T l.p~~ ~~t~>> ;... I 11 j j,.\.. 1 ~./.- : >---- : : 32011''... i....:_l;c-. ~l... i...,-:-:-~. f i i A i i,/ i i i 500 ~:~l i (}::i:t.t r r 700 rr x r.,. r r '\<J 'Y -r f ~. --. I ~ I : : : / : \: : : CJ : : :"" : T : : * 10-1 FIN AIR CHI.Ill 1.2.Ill (2 n 28.Ill (6 ( u Ill Ill Ill " u l.l Ill Ill llli.0 " Ill H FIN CJ AIR CHI... - MRS - MRZ MRB MRZ UBA u.(2.( & /11 11/ !;. - USA u Fig. 5./a Standard deviations.

59 -56~ P, hpa Differences of pressure Time 12...,....., ""["""!" '"j' nrrr: l/"!"'"1"'.i 10 1' '1"" r.., i :. i i i I Ill 'i'i. i i 14 I.. ~... :...:.... ~... :....!... ~...:.....:..., JH'.F~Y... ~... ~.. : : : ' li '1 V 'I ' ' I ' ' ' '... i 201''. j...!...!.....;... )... i ~/! ~. i!... ~-.. :. : '!'!' :t r- ;'t...!'... < I.. ' : : J VI IF. ' 321:,,,.. ' '... ',...,,~)ff}\' &::01'. <.". :-... -:...,...,...!... -~.. -r~... r;if.:... i!... j... j.. v I! :! ' :! I: ::.: i,/i,/'y j: \i.: r T...,...,.. l.~-----:_:j~-:~-~->::>~ :-',.:\:.1... r<:.. :..:.... ~ J ;...,...,... v~>r> y +... \ \ ~...,....,...,....,... Y... t~... ~,...,...;.. ij!""'t"1.. 1 : '.,../ '.~....//_:_ il! :_:.,l '.:. : i : : '!. : 1 I : ~~ : _.-- < ;/ ' ;,.---. ' \ : ~l~.. l,. l... ~_:_ '"~"' "i"""i'"' t-~y'-}'7""!'~_>'" ~ :,..,...,. _, ""! ~ 3"01 i : v>:;> ---I ~)/.; J.>--~----..,... ~...,...,... } 5;0 1 :.1 :,r:~--~~---_-_:_-_-_.:_!_t.i,...:_,.).i,/' ",_~_.,)\\ ' ' ' '! ~-.~<.~. c.:_:..!/ ~... ~ ~ / ~ ~~. l 700 r.:..:.'f:::::::-:.:..:;:..:_:_:_j.i.:_~"i' ":",?. <it...;.. "" l "" I" "''". l ' ---'---T---"--i.::::--i--.L : ' - -<_ -,:.._[...-,...: i. ~----~-2-..i.../ T--+---_1_::~ I rv~,o,,.._"!==""'""!'a! ' l * FIN AIR. CHI MRS FIN AIR CHI l-1rs MRZ U ll H~l " a.0 93 " s fj'/ ! se "'- MRZ t:..- USA USA l..( Fig, 5.8 Simultaneous pressure comparison, evening time (hpa1.

60 -57- P, hpa Stand. deviations. Pressure Time ' ~-r\1\ : \< r y r : : r 8( 11 I \ \ i \.i ~ i i i i 14 r r ~--~.; -:-.. r.. x r -r.. -:... l... 10S 0 11 \ i \ 1, i I I i i i i i 'J0 ftl'"t < T.:t!...'1"... 9"'"'"'..,...,...,..., J--~ f \ \ I I \ \ \ \ \ 11../l i \ i I I i i i i i 32 rr.:..:..:..:.1 -~.. tt :... Y.. 9 :... : ~... : r.. 11 \\-----~-- I I ~! ~! : 50,... ''.-~~-".. '-~.:: -:-.,._~.. ' "9+... '' j... j... ''.. ~.. '... -~... '. '. 11 i -,, i\!\., I i i i i i 70 ~-... j... >~n-...:.. v:j.:...:... j... -~... ~ : ii i \/ l i i i i : 11 i l: I : ;\ I i i i : :.,'\~-<... r :... r rr... :....,_t ~~--.. ;. I! i i '\ --~.! i \ \,_ i : i i 1401!'.. j....! "\_;.p r ~-:.:.. :... -~.... :... r i i./\)l! --.,_: i i i 200 ~... j... ;.,(<.. ~}... *... l\<:.:.".. ). '... '!..... i' '..... li i :... :y l\ i -.., i : : u ~ ~ \ 1\ ~ \ ~ ---~... 1 ~ ll' IN AIR CH I.0 98.iil ::[ r ~A2~~ti k~r : :... : 7 00 ~...,.. ~(-:-: ~:... c-~--~~->-~;:\t-~--~-:-:-~-hy~~~ \...[ i I i i i - ~J.., i -:-~-- : 99 9 ~ 0 11 : I 'f.._ ',, : --r--~ '?--?! ~.iil I : : : s i * FIN 0 - AIR. V - CHI "'- MRS ( \ ( ( ( i _- MRZ MRS l-1rz USA (7.(5 63.li a ( 1.( ll ( l.li l\ l.li li (.(4 48 A - USA Fig. 5.8a Standard deviations.

61 Temperature The temperature measurements at the one-minute synchronized intervals are absolute for all the participating radiosondes because they do not depend on the other parameters. They are determined only by the sensor properties, the telemetry peculiarities and by calibration procedures with the corresponding corrections. Four main types of temperature sensors were used in Phase III. The two Soviet radiosondes used a thermistor (10 mm length) attached to a metal support frame at the end of a plastic outrigger. The thermistor was held closer to the radiosonde body in the MRZ radiosonde than in the MRS radiosonde. The USA radiosonde used a longer rod thermistor (about 40 long) suspended from an outrigger. The connecting wires were thinner than those used with the Soviet thermistor. AIR also used rod thermistors supplied from the same manufacturer, VIZ. In the USA radiosonde the outrigger held the thermistor above the level of the top of the radiosonde, but in the AIR radiosonde the sensor was held much closer to the radiosonde body and in Phase III could not be above the level of the top of the radiosonde. Finland used a thermocapacitative bead mounted on an aluminised outrigger. The outrigger held the temperature sensor above the level of the top of the radiosonde. The Chinese SMG system used a bimetal spiral mounted at the side of the radiosonde. The sensor was surrounded by two radiation shields. The consistent differences between temperature observations for the four flight times in Phase III are presented in Figs to These are purely the result of differences in temperature sensor output including differences introduced in the conversion from engineering units to temperature by the systems Link radiosondes The same as for other parameters, the divergence between two reference radiosondes FIN and USA was larger in Phase III than in two previous ones. Thus, at night (fig. 5.9) the temperature

62 -5.9- differences at the level of 100 hpa was equal to and fluently increased up to at 10 hpa. Correspondingly, these differences were on the average of previous comparisons equal to and 3 0. At daytime (06 GMT) the obtained differences are at 100 hpa and 2 0 at 10 hpa. The summarized data of two previous phases were essentially smaller that is and 1 0. It is characteristic that at the intermediate times (00 and 12 GMT) as well as in previous phases the divergence of reference sondes was considerably smaller and, even in stratosphere, was equal to Table 5.3. summarises the differences between simultaneous nighttime temperature observations by the link radiosondes in Phases I to III. In theory, nighttime measurements should be easier to reproduce from test to test because there is no need to compensate for solar heating of the temperature sensors. Every effort was made to perform as many night time flights as possible in Dzhambul, to provide a reliable link back to Phases I and II. In practice, differences between nighttime simultaneous temperature observations by Finland and USA in Phase III were larger than in Phase II by 0.4 to at all pressures lower than 200 hpa (higher levels). Table 5.3. Simultaneous nighttime temperature sensor comparisons Finland-USA. Units: 0 0 Approx. Finland - USA Press. Ph I Ph II Ph III (hpa)

63 -60-;- Discrepancies in Phase III (compared to Phases I and II) were largest.between 100 and 32 hpa. Additional tests in the USA and in the UK have been used to investigate the origins of these discrepancies. Nighttime comparisons between link radiosonde temperatures in 1990 produced results very similar to those from Phases I and II. This suggests that there were substantial anomalies in the nighttime link radiosonde temperatures in Phase III. Changes in nighttime temperature sensor observations may have been caused by a change in s~nsor calibration procedures or by some other changes in sensor (radiosonde) properties. However team leaders of USA and Finland reported that radiosondes used in Dzhambul were of the same properties as in previous phases. About half of the nighttime flights in Phase III had rates of ascent smaller than 5 m s- 1 at pressures lower than about 300 hpa. These smaller ascent rates might be expected to produce larger thermal conduction, (self heating if present) or infrared radiative exchange errors than those typical of operational use. Detailed analysis of the nighttime data set obtained in Phase shows that the difference between the link radiosondes in low rate -1 of ascent flights (3-5) m s was larger than that found with -1. more typical rates of ascent (5-6.5) m s by less than 0.1 K at hpa, 0.2 Kat 30 hpa and about C at 10 hpa. Thus, the differences between the link radiosondes in the complete Phase III nighttime data set were III probably larger than for typical operational use by amount 0.1 C at 30 hpa and 0.2 C at 10 hpa. A possible additional source of ambient temperature error i.s temperature change caused by the balloon wake (or wake from the cross members of the flight rig in the case of comparison flights). In Phase III the radiosondes were hung at least 35 m below the balloon and this should have been sufficient to avoid significant balloon wake errors, as demonstrated in Phase I. However, the radiosonde suspensions from the support cross were much shorter than was the case in Phases I and II. The USA radiosonde was always suspended centrally under the support in Phase III and was the radiosonde most likely to be cross influenced by errors in ambient temperature from the flight rig wake. In future comparisons, suspensions of.at least 2 m should be used so that the possibility of ambient temperature errors from the flight rig is minimized.

64 -61- The summary of comparisons between midday temperature observations in Phases I to III can be seen in Table 5.4. Table 5.4. Examples of simultaneous midday temperature sensor comparisons Finland - USA. Units: C Approx. Finland - USA Pressure Ph I Ph II Ph III (hpa) Solar. El. There were more variations from minute to minute between daytime link radiosonde temperature observations in Phase III than in the previous Phases. It had been possible to check for this during the trial, the suspension lengths of the radiosondes from the wooden cross would have been lengthened to minimize shadowing from the wooden cross. The rates of ascent during the day were more uniform than at night and the results obtained should be typical of normal operational ascent rates. The reasons for the differences between link radiosondes in Phase III require further investigation. Nevertheless the analysis was performed according to the standard procedure Soviet, Chinese and AIR observations Nighttime Until the infra-red cooling errors of the USA and AIR

65 -62- temperature observations are more accurately quantified, the most reliable method of referencing Phase III observations to typical Phase I and II observations must be through the nighttime measurements of the Finnish radiosondes, given that these are 0 probably warmer than in Phases I and II by 0.3 C when observing temperatures lower than 220 K (-53 C). Although the Soviet radiosondes used temperature sensors selected from the same batch the output temperatures from the ground systems showed much larger differences than expected. temperatures at night were 0.6 C warmer than MRZ temperatures between 700 and 500 hpa, and about 0.3 to 0.4 C two MRS colder than MRZ temperatures between 100 and 32 hpa. In fact, MRS observations were warmer than MRZ observations by about 0.6 C between hpa at all the flight times. In the Minsk tests in 1984, an average of daytime and nighttime MRS radiosonde observations was. 0.2 C cooler than Finnish observations between 700 and 500 hpa [4]. At these pressures in Phase III the MRZ radiosonde observations had a similar difference from and Finnish measurements but the MRS observations were 0.5 C warmer than those of Finland. Errors may have been introduced into MRS observations by the Oktava software employed with the MRS system in Dzhambul or there may have been a change in MRS temperature sensor performance since Further work is required to identify whether the Oktava software was in error or whether these discrepancies are typical for all current operational MRZ and MRS systems. The discrepancies between the Soviet systems could be explained to a large extent if there were a timing error in sampling the output of the MRS temperature sensor by the Oktava software. The Dzhambul data set has been checked very thoroughly and the data samples at each minute in the test are consistent with the data used in generating the TEMP message by the Oktava software. Therefore, the discrepancies were not the result of faulty intercomparison technique. The algorithm used to convert engineering units to temperature in the AVK-I ground system represents the temperature sensor calibration curve more accurately than the computational process used by the Oktava software, but errors from should be less than ~0.2 C. this source The time constant of responce of the Soviet temperature sensor has been measured in the laboratory and also in special balloon flights by comparison with measurements from a thin wire

66 -~platinum resistance thermometer. It was found to be about 7 s at normal rates of ascent near the surface, and about 50 s at 10 hpa, i.e. between 2 and 3 times slower than the thermal response of the link radiosonde temperature sensors. In Dzhambul, the MRZ thermal lag errors relative to the link radiosondes should have been t0.2 C for the data bands centered between 500 and 140 hpa, near zero at 100 hpa and between -0.1 and -0.2 C at 70 to 32 hpa. If the consistent differences in Fig are adjusted to compensate for the difference in thermal lag relative to the link radiosondes, the MRZ and AIR nighttime observations are almost identical between 700 and 140 hpa. However, as pressure decreases below 100 hpa the MRZ observations gradually become warmer than those of AIR, by about 0.4 C at 32 hpa and 1.1 C at 10 hpa. MRS observations adjusted for thermal lag show the same trend in the vertical as USA observations between 700 and 140 hpa, but do not cool as much as USA observations as the lowest pressures. As with the USA and AIR radiosondes, the magnitude and variability of infra-red cooling of the Soviet temperature sensors require further investigations so that errors in various atmospheric conditions can be more accurately determined. In the long term the infra-red cooling needs to be taken into account in radiosonde error determination, as has already b~en attempted in [ 10] The Chinese nighttime temperature measurements varied in a similar manner to those of Finland as pressure decreased between the surface and 100 hpa, but at even lower pressures the Chinese measurements cooled significantly relative to the Finnish measurements. The Chinese temperature sensor has a time constant of response of about 5 s at normal rates of ascent shortly after launch. Thermal lag relative to the link radiosondes should not be as large as for the Soviet radiosondes. Using the same assumption as with the Soviet radiosondes, the cooling of the Chinese measurements between 320 and 10 hpa is estimated to be 1.9 C. This is not caused by infra-red cooling but is associated with the increasing time constant of response of the temperature sensor and poor ventilation through the vertical duct. A similar cooling with height was found with the Graw M60 radiosonde in Phase II [6]. This also had a bimetal sensor mounted in a vertical duct. The AIR temperature measurements differ significantly from the USA measurements in Phase III although the same type of

67 temperature sensor was used by both radiosondes. In earlier phases, Beukers and the Australian radiosondes agreed closely with the USA temperature measurements [6]. There may have been changes or errors in the recommended algorithm for deriving temperatures from VIZ sensor output, or differences may have arisen because of differences in the sensor mount and the effect this on infra-red cooling or heating of the temperature sensor. The infra-red cooling between 320 and 10 hpa was smaller for AIR than for the USA. Further investigations are required to identify the origin of the AIR-USA discrepan.cies in Phase III Daytime Details of the radiation correction procedures applied to Soviet and Chinese daytime temperature measurements can be found in Appendix E. AIR observations were treated in the same manner as USA observations and no cooling were applied. Analysis of the time series observations in Dzhambul corrections for radiative heating or indicates of :MRZ that geopotential height day-night differences in MRZ temperature observations were probably consistent to better + 0 than -0.3 C between the surface and about 30 hpa. Thus, the Soviet radiation corrections were producing satisfactory consistensy between daytime and nighttime measurements, but nighttime Soviet measurements do have some infra-red cooling errors, as noted earlier. In the layer between 30 and 10 hpa the 0 daytime temperatures were lower than at night by at least 0.7 C on average. The difference plots in Fig suggest midday temperatures were probably too low that the :MRZ relative to nighttime 0 measurements by about 1.0 C at pressures lower than 20 hpa. Towards the end of the flights at 00 and 12 GMT the solar elevations were similar at both flight times. Observations by Finland, USA and AIR are clustered together at 10 hpa in both Figs and At 00 GMT the MRZ and MRS observations were close to those of the link radiosondes but at 12 GMT the Soviet radiosondes output temperatures about 2.0 K lower than the linl! radiosondes. At 00 GMT solar elevation was increasing fairly rapidly throughout the flight whilst at 12 GMT solar elevation was decreasing throughout the flight. The AVK-1 ground processing assumes a fixed solar elevation for a flight, with the time of

68 -~launch determining the solar elevation used in choosing the radiation correction. At 12 GMT this procedure applied much too large a correction to the MRZ temperatures at pressures lower than 20 hpa. The Oktava software used with the MRS system was supposed to update the solar elevation as the flight progressed to aviod this type of error. In practice, the MRS observations indicate a similar fault to the MRZ observations. Chinese midday observations were similar to those of the MRZ radiosonde. Reference to Appendix G shows the very large corrections for radiative heating that must be applied to Chinese temperature measurements at pressures lower than 20 hpa. The correction depends critically on the pressure indicated by the radiosondes, so that errors in pressure sensor perfdmance directly impact the reported temperature. Chinese SMG data samples at 00 GMT and 12 GMT were smaller than for most of the other systems, since the SMT radiosonde was often flown instead of the SMG radiosonde. At 00 GMT the Chinese SMG observations were warmer than all the others from the surface to 100 hpa, but at 12 GMT the Chinese SMG measurements were significantly cooler than the others at all pressures lower than 500 hpa. At low solar elevations the consistency of the SMG radiation corrections was not as good as those of the Soviet radiosondes. On the whole it may be stated that the radiosondes MRS, SMG and especially MRZ, have shown a sufficiently good quality of temperature measurements in the Phase III. The slightly more accurate determination of the radiation corrections is desirable. The daytime temperature measurements at pressures lower than 20 hpa in operational Soviet and Chinese radiosonde ascents may not be as low as indicated from the Phase III results. This is because in the USSR and China the radiosondes are usually flown with a 10 or 15 m suspension beneath the balloon. Thus, heating from the balloon wake may provide warmer observations than those found in Dzhambul. The magnitude of balloon wake errors using 10 or 15 m suspension requires further investigations. AIR daytime measurements show similar positive temperature biases relative to nighttime observations as the USA observations. At low solar elevations, the AIR temperature sensor is much more readily shaded by the radiosonde body than the USA. For this reason, particularly at pressures lower than 20 hp a, AIR

69 -66- temperature observations at 00 and 12 GMT were much closer to those of the USA than at 18 and 06 GMT Reproducibility of the temperature observations Table 5.5. contains estimates of the typical reproducibility of temperature observations in the Dzhambul data set. In general, the variation of the reproducibility of the temperature measurements in the vertical was small. The Chinese measurements were an exception, but degradation at pressures lower than 20 hpa is to be expected with this type of sensing system, e.g. compare the reproducibility of Graw M60 observations from Phase II [6]. Table 5.5. Estimates of the reproducibility of temperature observations in Phase III of the WMO Radiosonde Comparison, derived from the standard deviations of the direct differences between the different systems. Units: C. Layer FIN AIR USA MRZ CHI MRS

70 -6?- Differences of temperature Time 18 P, hpa FIN AIR CHI MRS MRZ USA l<f~..-::~~~~1:~~ l... l.' H 1. -r. 1.. r..., ~)>~ r.. 1<.. : T -r-1.::<.1.. tr:.. r... i r :-.. r 1 >f r :, >\r I r >t~:~~ >< -1- l l l l/f r l 321,... N r! NK\ : t n i! ~:j. I I. J\) JTI~~~~ LI IT r.. :.. T : -r :.. r.... r-trir : r T r r :,...:,...:,...:,...:,... '4 \\ :...:,...:,... 9'l'ii-li' V\ ::../ i:..., :... :,..., :... :,... : =... ' I 1 I I I : I I \.. i I l,~l: J{ / I I I I I! 200,.. r r.. r -r r.. r ~.: r t )r;: r.. r..;.1.. ;... -:-... I : i i i i i \ i / i /l A i i i i i : 320 i.. :... ~... ~.. i'.. ~... :. 'ft.. tp V f' ~- '( "1'.. :... i"' ~..:... I = ' : \ : : : :. : : l r l n n \ : ::1 rr I: 1: I: \: : : : : : tjllj!q~yjjti JT I lili U lili 14t.l ( U lll9 us.311..(0 1S lli ( ( U )2.12.lili us li!iij.21.li us.lis li H li Uli :Clf~VI: ; I,,, i0 ~6: -2' 2 6 i0 i4 * 10-J. - FIN Cl AIR V CHI,.. - MRS (9 62 a - MRZ i :1. - USA Fig, 5.9 Simultaneous temperature comparison, nighttime (dgs}.

71 -68- Stand. deviations, Temperatur-e Time 18 p, hpa FIN AIR CHI MRS HRZ USA A 1011''... ' ~-... -~... -~. ''\'. ~ '<'t.. :... 'j'<,'... ~... O,... :... '5.;-V. 11 i. i \. i \ :./ :_: : ---~~--:---t : 11 : : \: \. ' ~ ::i J : r t(jlij;j~r r 11 : 1 : \..,:J :l. : \.\ : //!! i 3 z r... r....\.. :...r\: 1,>:~~~->P ;.. ;.. r.. r -... 'I -. ~-l: JJ1. -r. -..., r...,... -.,... I! :!! l! \ 'If~ ~! ~!! 50[... r..., 70 ~-,. -,.. -r _:_J-:;~;rK._., : - = -~- - ~::r,, J'{X r r : I r ::: ~ :! '}\V1; : :,, '! :...,-:,_y.. -r-t--.e.<r... :... ~... --;-... ~... -~... i r -, I :I \..,.,,.....:._- -~.. ~-.. r :.. ~.. I! '. I ) I p,... ~- : 9 r-~.i'f : &: 11 : l I l t'\ l -->--~ ; : l & ! lie & fll t;=v~il.- '*{ : ; : : i0 * 10-1 FIN D - AIR V CHI '\" - MRS llll Ill liS & li ill.46.li Sli ss i ' \ as Sii i MRZ ~ - USA Fig. 5.9a Standard deviations.

72 -6J- Differences of temperature Time 06 P, hpa. FIN AIR CHI MRS MRZ USA ' ::ft~~~~e~},_j J, A OY -;::: 3 21'.. r.. r.. :..... '\!'A.:. Ill.. ~... ;... ;.. r:.. ~ "?1' s I i : i \,-;\ i\ i i 1 i 1 : 189 1::1 J I I ~~~l f ill ~:~: I : : : : : \' l : I : :' : 109 ~::1 > T L T ;y~ix p{ I ~~: > r l f'i\jt(r > r ;a:' 5001 : - r -r -:- r,;t ";:;: r r ~2~ :::j :..! f l... r v ~ j ~ ~~ i0 * 10-l ( u l.u Ul ! lsiil Ull u -.15.lilf fill FIN!J - AIR V - CHI "' - MRS A - MRZ A - USA Fig Simultaneous temperature comparison, daytime (dgs}.

73 -70- Stand. deviations. Temperature Time 06 P, hpa! 10r!... r : r r >;:r.. r : /r r J>-r c~,l.>'~ 11../!!../: ; )''! _i.-----! l_...a' 14 rr.. 1,.. :..! r.. ~""..:.. : : ~P:.. :.. ~x L>v,.. ~.. ~ : : I' / ' ' ); : :.I:-<": : : : 11 : : : p /:.!,/:. )/! ' -.,} :. : 201f".!... :...!.. :;.; 't' :... :.. );;". '!".. :)T' :... J.:.:.:."T'.. :...!'.. ~ r I' : : : J : I : : / : :.- ~ -~:..-- : : : : :..,. + :{ r~")p<~ 1 ~;:~~T.. I...,... :... j... j... L.j. \.j. j..j. 50~ L \4.\ ~(~ '\+<~.\..j..-~h,.[ 11 :. :\ f ).l f h)----t----: : :. : t j 10 rr!' : : A.:._!- : :.. ~ '\,. : : :!'!.,.!' : 11 : : : b<r : \.; : : :, : :, 100 [' r. J : Jt-r :./,r: > r r 1 -r,.. : r r... rr ~r. r : v"~f~-~~~~j"''[' -r :.. r 'j'"'t 200 t : ]i t*\'ii~p> i : :, 3 20 rr ;.. r rr.. r 500 ~ l H~.:Ai.~~~~~~I~~r.... lr: : r r :.. -:- T.. : r r.. :- i -:-,. : : l r... -:- "' :.y~;rt L~l-~~~~~L~~t~-~...:.. :... r 11:!'(V!.. ':--_, '-_:'... 78:00 [''' r ;:) I..... ;.... FIN AIR CHI MRS MRZ USA llli.01! 109.1! ! (.lllil 121.lilll il 1.09 l u ss & ( ! ( ( ss lsii H.( (7.6.( ! : : : i * 10-:i D V.._ FIN AIR CHI ~- MRS A - MRZ lili.48 u liS U ! (6 71i lll8 11!8.60.lili lll 11!8 _.(8.(8.ss Sli lil.38 Ill ( (9.53.ss ! (2.31i 8.( (.(0.till.(1 li9 67 A - USA Fig. 5. f oa Standard deviations.

74 -71- P, hpa Differences of temperature Time rr-<~~~l ' : r r : r r... { r-:~t~:~1~ r I! :-----_!!!!!!\/! 't\--..! 141"!" r -r-~~<~j" 1 ~:>~~i~~~~l~-! r ' l -r 1 -~~- r tt 11 \tr "/)J I:!! >-...!!! : L! t\ \ 321"\'"'''''j'''''"]'"''''"i"'''"'['"'"'j'"'''''j"'''~,]- <..,J.i\; ~ 1: : : : : : : : -... y.; 1 n 1::11111 t I I Jt~~ :...,... l... i...:... V ff ~~.. 200!""... ~... \...,... ~... ~...,...!..'i':f'p.. _l. "V.... I~ I j f ; i V /l )f /j li!.. :!!!lf/!jl/! 3 20 r-.... r ~... : : ; :.... : w : -~n-~ r : : ' : : : :u: w: I!!!.!!!!.//1!!I/! 500 n... r... T... r... ;... T I: : : : : ' : 'i! I : I\ :... : l'ft"'i''l\.. ;. 7001'['... t... \... [... t... i ?f.. 'f_:.:j.:.:..,?. i.... I' : : : : : : *""--\ : 11. I! j ' ' ' l f. \ j // FIN AIR CHI MRB MRZ USA -. 2.( i BB ! SB u I j, rr-"!-"'' 4! l -2: * 10-~ Cl - FIN AIR CHI " - MRS.._ MRZ ss li ll lli !18 41i IJ. - USA Uli Fig. 5. i1 Simultaneous temperature comparison, morning time (dgs}.

75 -72- Stand. deviations. Temperature Time 00 P, hpa FIN AI.R CHI HRB HRZ USA ' 101!'. ~- : -~ : t~';;.t : p : j! -~.:.. v n ~ ~ : i t.-~--~ _ i = ~ _; : : : : : >-. ~---_; : : : 14 [...,... I... f... r -:.:.~;::~--~-:[.:.. ~~J -~<<{:.....!... l 20 [. r ;.. : -:-.. 1 ~<<I ;...::;z.. T>~"L~~~+:_~~'-r 11 : : : : :1 : /_:;: r : : : 32 r,... j... t... :... r... r..:.r-f t>~~: T... :-... \... r : :. :!,...-: L/~ \' : : 50[...,... I... I~~~--(-~jf.. J-~7 <:.!... jl... ]'... I 70 ~- : : ;r : r t 1,;~:;><~... r.... r : : i 100 ~,.j. ~".. i.... j. k;v(~. :.. t... P j. \ f 11 : :\ : )l' "",.. t-... : : /' :. : : ~::~ r (J~1~I?~ 1. r.00 ( liS li u l.ll IH 5» ( lj S li u Ji :::[ r \lt't ~ i 11. : \j --:,,k,l :. >. : >! : :. : : 11 : ~\!'~,~~: : :. :...:... I... i rr... :... :... rj :.. :.. :f.:.. ;rr-:.;,...!... :..., 8 50 ~ : ;::bl~..:.<..,..,""'!----!-""!--!'-~~--;. I ' ' * 10-l. 11! [J FIN AIR V - CHI MRS A -.sa !H liS MRZ!>. - USA Fig. 5.11a Standard deviations.

76 -73- P, hpa ' Differences of temperature Time f. ~-<~~~~-~~~~~F~~~~-~-1~... I~~>~~+~~~;-~~-.) r< r r r<~:-~ :.,.<-~.- :~'\' 1 r/'1. I \!!! --...;, \... \ \ \ I/ \ 'f<.~~.. :.. 1..! J;.-<~~<L., :.... ~<.1'.... I : --- : : : ~- : -.I : I... i \ >~-~ \ l "l- ~-l~. \ l ' -~ ; r -~-<.l. : : l~ : r 1 q; I!! ; -...! i I \'-... l!! \ 501"'.. -~... -~... ~ v<... ~... t.. -~ ""<"-~'... f-'..!"... r.. : I i i -- -.!. l \ \}::\/ : 1..:... :...!... r~-<. r ~'\.. ri~~ r.. r 70 r 100! I., : I.. >'\.~_1 rli l\1 >~-- 140,1... -~... -~... j... :... \... -~ j.l.. t!... '~'..... I I < l~ : : : : 'I \:I I l I l l! [ [I b I/'! :::1, r r : z r~l\ 5001"'"'"!'...!... "'!"'"""'"!""'"'""'"!'~... -:If~,... ~... T""" I ) ) ) i ) \..,//1 i l! I I : : : : : i'" l! : I : I r- T.. : :..: >j,i'\.l Ll... ~ I ;/../ 11 /~ ~ y ~ 8 50! p:;-v"*7ll.-";--,. I ' ' -~0 -i0 ~ * i0-1 FIN AIR CHI MRB MRZ )7 IH -."" Sii.ss u i ss i -.09.liS i !112 -.lib.li0 -.(/J ll ss 30 4li lis - FIN c - AIR CHI "' - MRS.a. - MRZ t. - USA UBA u H/J li4 Fig Simultaneous temperature comparison, evening time (dgs J.

77 Stand. deviations. Temperature Time 12 P, hpa FIN AIR CHI MRS MRZ USA i 10 rr r T"l' r r.. r.. r >rpj>t r r -r.. r... r.. : r r T.00 1> Ul UJ ! lil u rr r r :\ : /tl r : :.. : r -r r r.. r r.. r r 100 ~, r fftffrr' 'r I! r' I : :- r ~ : 1 r Jlr r r : l -~... r r r :.. r 11 : :.1.m r: : : : : : : : = : = : : 200 ~- '! : 1~M-~:~.r r l -~ : :,. r l 1 r r.,. 320 n r :.. :rl~>~r -:-... r : : : : -:- :..:.. :.. : r.. r r r r '~Y Jr : \., :.;. \.\..;..; I!'.; 11 : : 1\l ; j' : : : : 7001l'",... 'f!/.',,..., ~ "'!...,...,... :... -~...,...!...!'.. ; i j /.. f+----l\ : : :.... il : /' \\ : :-M>;:-.i ;. 850 Jll : '\""!-'l~a'!=a,-!,-~~-!'--'-'!-...""'!--!-~-!-""'!-=p I ~ 4 : ~ 8 10 i ie * Ill FIN D AIR "l - CHI "' - MRS - MRZ l H llll Ill ; ;, - USA Fig. 5.12a Standard deviations.

78 Relative humidity The accuracy of relative humidity measurements is known to depend on the value and sign of the gradients of temperature, relative humidity and pressure and other factors such as influence of cloud's water and solar radiation. During a radiosonde comparison test the relative humidity in a given range of pressure levels in the troposphere sometimes varies over a wide range of values. The analysis techniques used for other meteorological variables (grouping simultaneous comparison data purely according to pressure level) do not take into account this variation in relative humidity. More characteristics of detailed analysis is required if the the relative humidity sensors are to be adequately examined, see Table 5.9. The distribution of conditions experienced in Dzhambul during the comparison can be judged from the statistics in Table 5.6. Relative humidity near the surface was always low, as could be expected in a semi-desert region. Relatively dry conditions predominated at other levels although in a small percentage of flights the radiosondes did ascents through clouds. This contrasts with conditions in Phase I when about to per cent of the comparison flights ascended through clouds. The relative humidity sensors used by the radiosondes in Dzhambul were of three main types. Finland used a thin film capacitor sensor (Humicap) mounted on an external boom. USA and AIR used the same carbon hygristors manufactured by the VIZ company. These were mounted in ducts at the top of the radiosonde, but there were significant differences in the size and shape of the ducts. In the more modern operational VIZ radiosondes the duct design has been changed [12]. All these sensors have time constants of response of the order of 1 s near the surface at normal ascent rates. The Soviet radiosondes and the Chinese SMG radiosonde used goldbeater's skin sensors. The dimensions and shape of the sensor surface was the same for all three radiosonde designs. In the Soviet radiosondes the sensors were mounted on top of the radiosonde with the sensor held horizontally. The protective cover of the sensor differed between the In the Chinese radiosonde the sensor surface was vertically in a duct at the side of two the radiosonde. constant of responce of the goldbeater's skin sensors designs. The mounted time has been

79 -%- shown by laboratory experiments to be between 6 and 10 s near the surface at normal ascent rates, with the response depending on a variety of conditions. For instance, the time constant of responce has larger values when observing in moist conditions than when observing at 50 per cent relative humidity. The time constant of responce of all widely used humidity sensors has a strong temperature dependence and pressure dependence. The response is also influenced by several other factors. Thus, the typical time constant of response of relative humidity sensors increases much more rapidly than that of temperature sensors as the radiosonde ascents, e.g. time constants of response for relative humidity at 200 hpa can be shown to be more than 100 times larger than the time constants near the surface, whereas the time constant of response of temperat~e sensors at 200 hpa is typically about twice as large as at the surface. All the statistics discussed below were calculated relative to FIN Effects of differences in speed of response of the relative humidity sensors Although conditions in the Dzhambul test were relatively dry, many comparison flights showed significant variation of relative humidity in the vertical. Examples from individual flight records are shown in Figures At low levels where temperatures were higher than -10 C the vertical structure indicated by each radiosonde system was similar in most flights. Flight 45 was not so typical because the radiosondes ascended through a thin layer of cloud, with enough liquid water content to cause wet-bulb cooling of the temperature sensors above the cloud. Neither of the goldbeater's skin sensors was able to respond rapidly enough on emerging from the cloud top to accurately define the hygrolapse above the cloud, see minutes 12 and 13 of Fig This was probably the result of slower response in moist conditions and also possible moisture contamination of the sensor mount and covers. The effects of the slower response of the goldbeater's skin sensors at relative humidity close to saturation can also be seen between minutes 5 to

80 -77-8 of the same flight. The differences between the Finnish and USA/AIR measurements above the cloud top, minutes in Fig. 5.15, were often observed in Phases I and II in ascents that encountered liqiud water in clouds. In these flights the carbon hygristors indicated lower values than the Humicap by between 10 and 20 per cent R.H. for many minutes after entering the dry layers above a cloud. It is not yet clear whether this is because of an error in the USA or in Finland measurements. When the radiosondes did not pass through a cloud, these two types of sensors normally indicated similar values or in very dry layers the Humicap usually indicated lower values, see Figs and At lower temperatures, from -10 C to -40 C, errors introduced because of the larger thermal lag of the goldbeater's skin sensors become more easy to identify, see minutes 21 to 28 of Fig and 21 to 25 of Fig In both cases, the time constants of response of the Soviet and Chinese sensing systems were to be in the range 1 to 4 minutes. At even lower temperatures and pressures in Fig. estimated 5.13 and 5.14 the relative humidity indicated by Finland drops to near zero, but all the other systems indicate substantially higher values. This was typical of all flights in Dzhambul and was also found in most flights in Phases I and II. Finland relative humidity observations would only remain at values significantly larger than 5 per cent in the stratosphere if the radiosondes had ascended through heavy rain or icing conditions. The time constant of response of the goldbeater's skin sensors was estimated to be between 5 and 10 minutes when it was assumed that the rapid decrease in relative humidity indicated by Finland was real. This speed of response for goldbeater's skin at these temperatures and pressures is consistent with laboratory evaluation of the sensor characteristics. Thus, there is no reason to doubt that the changes indicated by Finland were real. Comparison of measurements by the goldbeater's skin sensor of the UK RS3 with those of Finland indicated similar time constants of response for goldbeater's skin in Phase I. The response of the carbon hygristors to the decreases in moisture, between minute 30 and 32 in Fig and minutes 24 and 26 in Fig. 5.14, suggests time constants of response of 2 to 3 minutes. These time constants are

81 -7cf- 2 or 3 times larger than those estimated for Finland from earlier tests. This contrasts with the situations a few minutes earlier in the flights where the speed of response of both carbon hygristors and thin film capacitor to a rapid increase in moisture was identical. Examples of this sudden degradation in the speed of response of carbon hygristors relative to that of the thin film capacitor were also observed in Phases I and II. The origins of the effect need further investigation. Thus, the thin film capacitor of Finland had a better speed of response at lower pressures than the other sensors. However, it should not be assumed that it retains this sensitivity at pressures significantly lower than 200 hpa. At these lower pressures further investigations with equipment specifically designed for humidity sounding in the stratosphere are needed to assess the accuracy and response speed of the thin film capacitor measurements Summaries of statistics In order to simplify the presentation of the processed results differences against the measurements of Finland have been used. Processed statistics have been limited to temperatures higher than -40 C and pressures higher than 250 hpa, selected using the measurements of the Finnish radiosonde. Typical mean temperatures and relative humidity for the Phase III were 20 C and 27 per cent at 900 hpa, 9 C and 40 per cent at 700 hpa, -10 C and 27 per cent at 500 hpa and -34 C and 20 per cent at 300 hpa. Relative humidity varied most at about 500 hpa. Differences between the relative humidity measurements have been classified according to pressure levels in Table 5.7 according to temperatures and also relative humidity in Table 5.8 and in terms of relative humidity for each temperature range in Table 5.9. Selected data from Tables 5.8 and 5.9 are displayed in Fig From the mean differences in Table 5.9 it can be seen that: - in moist conditions the goldbeater's skin sensors always indicated lower values than the thin film capacitor and the

82 -7Jhygristors, usually by between 5 and 15 per cent; - for relative humidities between 25 and 75 per cent, all the relative humidity sensors usually agreed on average to better than!3 per cent at all temperatures. The main exceptions to this were found with the Chinese measurements. In most temperature bands the Chinese observations were between 5 and 10 per cent lower than the other sensors. The Soviet sensors indicated values about 5 per cent lower than the other sensor types only when at temperatures between 0 and 20 C the relative humidity was between 50 and 75 per cent; - for relative humidities between 0 and 25 per cent, and 0 temperatures lower than 0 C all sensors apart from those of China indicated relative humidity larger than Finland by at least 5 0 cent on average. At temperatures lower than -20 C all sensors indicated relative humidity larger than Finland by at least 10 per cent on average. As noted in the previous section, per the positive bias in many of the goldbeater's skin observations originates from the slow response of the sensor relative to the thin film capacitor. Later tests have identified that at the lowest relative humidities there was an error in the algorithm used to convert the engineering data from the carbon hygristors to relative in Phase III. This produced a measurements at low relative humidity. that: positive bias in USA humidity and AIR From the standard deviations in Table 5.9 it can be seen - In nearly all categories the smallest standard devations were found between AIR and Finland observations. These radiosondes had sensors with similar speeds of response at most levels, and relative humidity was sampled at rates close to once every 2 s both radiosondes so that interpolation errors between samples were negligible. Comparisons with AIR have less scatter than with USA in general, because interpolation necessitated by the uneven sampling of the USA baroswitch system occasionally produced significant errors in the USA observations, e.g. see minutes 12 and 13 in Fig The reproducibility (1 s.d.) of relative humidity measurements by Finland and AIR radiosondes must have been better than 3 per cent for relative humidities between 25 and 100 per cent. by

83 At temperatures higher than 0 C the typical reproducibility of goldbeater's skin measurements varied between about 5 and 7 per cent depending on the relative humidity. 0 - For temperatures between -20 and -40 C the random errors (1 s.d.) in goldbeater's skin measurements were typically about 10 per cent. The scatter in MRS measurements relative to Finland appears similar to that for MRZ measurements. This is deceptive. The MRS system only samples relative humidity for 25 s every 100 s so that if signal reception is poor and a few samples are corrupted int.erpolation must be performed between samples many minutes apart. For this reason, very large errors resulted in several flights in Dzhambul. These flight data were eliminated from the final data set because they would not have provided an accurate representation of the perfomance of the relative humidity sensor itself.

84 -81- FLIGHT 24 hilinidi ty FIB AIR CBI MHS MRZ USA M ( 36 2'{ ! FIN Cl - AIR V - CBI... - HRS A - MRZ A - USA Fig vertical profile of relative humidity (X}.

85 -82-- FLIGHT 45 humidity FIN AIR Clll HRZ USA 30''. ".. " :... ". '9' ~ ".. 'l"'.i{"""...,... "... ~".."'... :... "...!"... ".. :... "...,... ".... ~ ;,. I ~ I I' : ~ 1 I t tjl ~ l 4; ll : I I : i V " f.?: ~ ~ 11~. t ~ j \ 41, I '.. 1 ' ~ t ~: \ ~ I \.. l I : l j\ :.. I ~1 ~ * i 'f\ ' ~ :. :. 251.:. ~ ; Y ~ s: : r.,. ~ : : : ~ I 1.;! i! 1 \ ' I 'l't?~ Y'r! I i I ~ ~\ I I ' t 9 ~ ~": 'i' l ~\! l ; ~ \.! I 'Ill t o ' ' 4-.! : \... I i! \~... : ~ ~. 201 :.. l<)l,.... ~. L\~:~J..: r...!...,... : ~... ~~ ' L ~1~::-=--~---- r-~~~:~±:-~_, I t:ja..~- : ----~- ~.;, \. : , I ~.--~.f ---,.rt 99 i ~! // ~/t /! : r r.,. :! : \. :, ~:.:..:. :\:;~~~:~-~;~ 97 1 I ' ~ ' '\~-----: ~- _ ~?.. ~?<1...,... :! I, ~:::--:- ~.~ ~:.. i ~-----=---~= ~==---=.:::;::::::t-- L.~.. I : ~ ==i;-g!&=:.._i 10 1 I ~ '~' : y: g. t 100 I. A./ L-4 A f~~~~ I?:t~~~;:~---r 43!./:;,:o:~~--<-. I ~~ o_ l.. ~_./ 0 A.;,.,.~-~~-=!---.._,--!-= ; *10 1 B - FIN ~ - AIR V - CHI L - MRZ A - USA F i g. 5, 1 4 Vert 1 c a 1 pro f 11 e of re 1 at 1 v e hu~1 d 1 t y P: 1.

86 -83- FLIGHT 58 humidity 0 ' t *10 1 FIN Am CHI HllS HRZ USA Fig, 5.15 Vertical profile of relative humidity CX}.

87 Huroidi ~ :J sensor's pet"tmance a\ all i:e.'fllperaiufes above -40 C a) Humidity, %RH Huroidi ty sensm 's pedomance.3\.all humidi "ties b) lo.o lmean c!~~erence_. %RH I 7.5 ::~~ _ "'..o:;:_,, "!"',..,<~"'" -- -,~HI-F'tc' C..._1._._,:;:-, _., ~ V.1 "'I n n~....,_, --,~.:-----~-- ~ - AIR-FIN "\ -2.5f -...,'c:.:-::-::~~ tirs-fit l "'n~ '. - -'!P.7-FTt l :~~~-Flt l ' ~~ :,t.. ~ , Hurtddi t':! sensor's pertortoance in c c> f-lean dl -He fence_. :-;P..H '.: -_ ~-,..,.~-~~~::~~ - ~. ~~~~~~:~ -i;t ~_ t 1RS-Flt-l _1r::E -~!RZ-FH-1 ''"' t: ,...---usR-Flt-l Humidi t :J.. %RH Hur1lidi i':j sensor.. s perfomance in 0 25 :~RH d) "' Nean di Herence_. :~RH 1.J - lo~ ~"- - au-f!fl "i 1:: _.,...,;,_;~;_: ~, - AJR-Flt-l,... _-~ '- _-_ --.';:.;;:_.::.:--._ MRS-FJt.l 'I ---. " ~._ 11 1 ~:-:--"'~(-NRZ-FIN. r --.. _._.\ ~---usa-f1t l Tel'i,perature_. C Fig Hu~lidiiy sensor's perfol'i ani:e

88 Table 5.6 Distribution of simultaneous humidity differences (XRH) relative to FIB within different temperature and humidity ranges (numbers of samples)!humidity I USA HRZ HRS AIR CHI I ac! I 0,, 25X ,, 50X X ' '1 oox 11 H 2 ll 5! -20. '0 ac J o. '25ll ' '50ll ' 75ll ll [ o. '20 ac I o. '25ll " 50ll ' 75ll ' '1 oox '40 ac I I o. '25ll ll X ll ll ll

89 Tat le 5. 7 Means and standard deviations of humidity differences relative to FIN (XRH) at pressure bands: , , , hpa p USA HRZ HRS AIR CHI hp a lm! Sd Hn In Sd Hn In Sd Hn lm! Sd Hn In Sd Hn 900 o U4 m o ,90 6. n !5 U t m 300 9' ! ' Table 5.8 Means and standard deviations of bumidity differences relative to FlH!XRHl at temperature and humidity mges separately USA HRZ MRS AIR CHI Range Iml Sd lm! Sd In Sd lm! Sd lm! Sd C o c 'C Q ! c X sox ' 75l! o toox s l3. 27! t.!

90 Table 5.9 Means and standard deviations of humidity differences relative to FIN CXRH) at temperature and humidity ranges I USA MRZ MRS AIR CHI l I Mean di :ff erence, XRH I o oc oc o.. 20 oc oc oc oc o. 26 o.. 20 oc oc % oc o oc o.. 20 oc % oc * oc o.. 20 oc I Standard deviation, XRH l o oc o oc o.. 20 oc oc Y oc o oc o.. 20 oc oc oc oc o.. 20 oc oox -40. '-20 oc * oc o. '20 oc

91 5.5 Wind Wind is a very important meteorological variable. Upper wind observations have a very large influence on the accuracy of numerical model predictions. For this reason, wind observations are often made more frequently than temperature and relative humidity observations in the operational upper air network. In Dzhambul three different methods of wind observations could be compared. These were secondary radar (USSR - both AVK and Meteorit and China Type 701 radiotheodolite used with transponder). Radiotheodolite (UK-AIR) and Omega Navaid (Finland). Fig shows an example of a vertical profile of wind speed and direction for all the systems reporting winds. In this example, values for AIR were not submitted once the tracking 0 elevation fell below 20, see section (The AIR radiotheodolite is not well suited for use at stations where tracking elevation often falls to values lower than 16, but is satisfactory in the Antarctic and in many tropical locations). Between minutes 15 and 35 in Fig. 5.17, the Omega wind directions do not follow the values indicated by the other systems very closely. Under these observing conditions the secondary radar tracking should be not reliable. Thus, the discrepancies are an indication of errors in the Omega wind observations. The large scatter in wind direction at minute 6 and at minutes 64 to 70 in -1 Fig is associated with wind speeds less than 5 m s and does not produce significant vector differences between observations. the wind The AVK-1 system was the most reliable of the three secondary radars for height observations in Dzhambul. So the wind observations from the AVK have been used as the reference against which the wind observations from the other systems have been differenced. In 1990 it was realized that the time assigned to an AVK wind observations in the original Dzhambul data set was time at the end of the tracking data used to compute the wind. However, the wind should have been assigned the time at the centre of the data sample used to compute the mind. The samples of AVK winds in the final data set were recomputed to eliminate this. timing error. The results of processing the differences between the different sets of wind observa bions are illustrated by the scatter of the vector differences and histograms for the meridional and the

92 -~zonal wind components in Figs Northerly and easterly directions have been taken as positive in these plots. Each scattering diagram includes a constant probability ellipse which contains about 50 per cent of the distribution. All observations between 700 and 200 hpa have been grouped together for convenience. The data should provided good indication of the typical accuracy of windfinding measurements in the The data from 06 and 18 GMT ascents have been separately. troposphere. presented Systematic biases between the secondary radar winds and also the radiotheodolite winds were generally less than 0.5 m s- 1 in each wind component. At 18 GMT the Finland easterly wind component showed a significant bias of -1 m s- 1 see Fig. 5.18a. This magnitude of bias has been observed previously in Finland winds in Phase II. The height of the ionosphere changes between day and night. If this change occurs along a major part of the signal path from the Omega transmitter to the radiosonde during an ascent, erroneous phase changes are introduced into the signals received by the radiosonde and produce systematic bias errors. Propagation changes along the signal paths from Liberia and Argentina were probably the origin of the problem at 18 GMT in Dzhambul. At 06 GMT there was no significant bias in the Finland winds. The variances shown in Figs and 5.20 indicate that for the conditions between 700 and 200 hpa in Dzhambul the random errors in wind measurements were of similar magnitude. These -1 errors were less than or equal to 1 m s in each wind component for all the windfinding systems. These values are smaller than the standard deviation of the difference between numerical model first guess forecast fields and the observations from Dzhambul at these pressure levels. For instance in August 1989 comparisons of operational observations with ECMWF first guess fields had a typical standard deviation of 3.2 m s- 1 for each wind component. The radiotheodolites and secondary radars can be expected to have larger observation errors when tracking flights at low elevations, conditions which occur more frequently at higher latitudes than Dzhambul.

93 -30- FLIGHT 24 direction FIN AIR CHI MRS HRZ USA 3l!i fi S & \ fi ! lH 2.( )( !! ( ll > !ili i 271 2U lis u < Ill - fin. 0 - AIR V - CBI.., - MRS A - HRZ.o1l. - USA Fig Vertical profiles of wind. a) direction (dgs).

94 ! FLIGHT 24 velocity 7l11r T, 1 r 65 r. r~ -J1- r )'...!... -~...,... ~...!... '!.... : : "'-~-: ~! : -.a... ~ I ~ ~ 'f~--..,_-~ i i i ; i ~~,.... : 60 l 1 ~ q~~a r -r 1 1 r I'Ll:~''''... ~t~~~~~~~-l... l... [ j...! I i ' i i J:...--~ i i 1 t L:r:.-;;::.--JA t j t ~. j~~~v1.! I :1', ~-L, 11 I : : : : : : :.a...,-v~..,.:r 40 1 r, r -r 1 1 r ~$ I ' ' ' ' ' ' : '}_..-'+-.,_ 351 r : l ' =~~-v I '.. ~~~-:--v- ; ~.~r~ai 1 l r I : I {~~ l l l l I., t'-', ' :, : 251'... ~-...!... t;:~y t... ;... ~-... '!... t.... I! i...a-'"ti i! i i I ; ;,- ":"""g_::.~"' ; ; ~ ; ; I i 'rz.'yv- ~ I : :f~t : 20 I J ~Al! r j ~ ~ 1, it't:!fj ~ 1 j j l 1. i ts ~I. i.. i... i 151"... ~... "~;t:s:.:~_'!... -~... :...!'...!... -~..... I, a-~:f.,,,, ' I l :r--:- i'f)f \ ' l ' 1 ;..,;::<!.. ;, ;,, i 1 r 101.;... "' ~,:_ : + : =,::$-.:ry' : : : : : I '-~~~-"' 1 i :! r~..:r-; ;. ;... 5,--~~;:~~~ l r -r J I I I! y-:r-:::...-::-.i.. ~ ~ I _L.~~--""' ; ; f21~a 5 ie is 28 i5 J+J 35* FIN Cl - AIR V - CHI "' - MliS A - MRZ... - USA FDf AIR CHI MRS MRZ USA B s B 4 5 s 6 li 7 li lll llil lil /l li ll 82 8ll 36 ss 81i ss 88 31i 37 Sll '1 Sll ss Bll 88 ss SI! /l lli 19 lis ! lli ( t il 9 9 llil 1lil 9 B llil 11il lll lil il lil 8 li li 3 li 6 5 li s 7 1 I Fig Vertical profiles of wind. b) velocity (m/s)~

95 -92- FlH - MR:Z T s + ' Tiltil ~8 P:ressu.:re 701it - ;jlliflif S-H avera9e:.1 val!>i.anoe: E-N avel!."age: ,a.l!Oi.anco&:.LG0 Co:rx-e I at ion; none- Points: 5~9 J. I t t-5 I AIR - MJ\.& 5 t.t '... t TiM ~8 P:r~ssu~~ 7~~ S=H av~ra~e: =..1 ~J:u i anne; S:5 E-W &..!!era;we:.1. ya.r-i &nc,g,: 74 CorP 1&~ion; -.~1 Point:;;:: &?4 Fig Scattering diagrams and 50% ellipses for time 18

96 -!13- CHI - MRZ 5 Ti-.18.F~e~~u~e 7UU S=H av~rad~: -.2 varoi anoe: 9fl E-W ave~ag~; roianoo~t:.05 co~~lation: -.96 Points: ;IUH J., I i 1. I P:res;~;;u~e?1110 ay~ra:!ij~: S-H E-H varolanoe: a.ver'a.g'e:... ar-i&nc~t: Co~l&tion: Points: a.oe Fig Scattering diagrams and 50% ellipses for time 18

97 H-S component 31.3' :1. i I i!! FIN - ftrz I I 12.5i! 15.4'l. ft.8'1. H.frl. I i "! 2. 9'1. I ' h1.7;: i 4.8'1. i I 8.6:~. ' ill l! -5-4 _').J E-ld COPtponent 38.8' '1. n & H fi H I FIN - MRZ lii====i! 8 2Y. fut1. IUt1. ~-== s ws Fig Distibutions of wind differences for time 18

98 H-S COMponent :t. ;== AIR - ttiiz 34.3" '1. 8.8'1. 8.8'1. ti z.2'1. 5.5:1. Uti '1. 8.lt/ Z litis 44.2' "1. n I i I 9.5:< 8Jt;. 8Jt;. 8.4/. r 4.4/ z U:l'J. I 8.8'/. 8JtJ !Ills Fig Distibutions of wind differences for time 18

99 -:16-4.6/. fut;. tutj. I 11 rt-s COJ!tponent n 58.8'1. I i I' - I rl".1:<. u - I il - ~ I I 9 I ~ 7 ::t ' I I,..,_,.,. B p CHI - l1rz I I 2.7'/. " 8.41! A 8.8' E-W coi!iponent 52.3'1. CHI - MRZ 17. 7'!. ~ '/. 3.11: IUh: l _') x ~ 8.4x 8.4A 8.4'l l!lls- Fig Distibutions of wind differences for time 18

100 -!17- H-S COMponent 41.1'1. ;::== rtrs - ft1iz 71.8' '1. 5.8'.1. 1.Z'l. 1.1'1. 2.5x I 8.4/. tuh: 8.8' J!!/s E=U ~WMpom:mt lm8 = JJ..RZ 38.1'.1. n I 48.2:t. 9.1'l. 9.5'l. 4.1'l. 2.1t. I 2.5'l. 8.tt;, r --~ x I lutj J!!/s Fig Distibutions of wind differences for time 18

101 -38-.,. ~. -;:; o.. ~ o, 0 0 Ti- Q6 PX''i'SSUIX''i' s-h averase: -.1 uajt>ianoe: L15 E-W avex-age:.4 II.,II&Jt>ianctt: 1.12 Co:r:r-e-lation: -.J.? Points: 378 l I l..j.. -5 I tlih = MM~. 5! l TiFI'i> W6 P~ssure S-H average: -.4 YaJE>tano;!;!:.!.af> v.u i ano>fl<: 1!.5 co:r-rw&ation; -.19 Points: 18{6 or I t-5 I Fig Scattering diagrams and 50% ellipses for time 06

102 -!l.9- CHI - MRZ r TiMV 06 P~~ssure 790-2~~ S-H averase: -.3 ua.lt"ianoe:.l.ma E-H ave~age: -.5 V&lf'i &fhhi': co~~~!atio~;.10 Points:.167 l. I. t t-5 I I MR~ - r MRZ l -r. : TiM'ii' 06 PreliPSI.llt'e s-n..ave:r-a:5,n:. : -.4 ua.l!'ia.noe:.l.lb, E-W aver<a:llfe:.1 va.l!'ia.noe:.1. :u Cozoll:"<il'l&tion ~.15 Point:~>: :&64 I J_, Fig Scat.t.er ing diagrams and 50% ellipses for time 06

103 w's o.sx I I I.. - I I ' 4.lt/. l.l. 'n L1x. 8.S:t. Lb: ~- ~~~--~---= ws Fig Distributons of wind differences for time 06

104 -101- H=8 em~pontmt AIR = HRZ 53.1:1. r=== 12.l.tt I ' Zb.8"1.!- I I 8.6/. _j 2.2Y. 2.2Y. 1.11: tuix 8.6/. 8.8/. J!t M/s E=U eu~pm~ent 36.3' '1. ;:== A IB = MBZ 8.ttl. 8.6:1. ~ft.t< 5.ttl. 1.7'1. 2.2/. Z.ZY. I! 1.1:1. -s ws Fig Distributons of wind differences for time 06

105 N-S component C:H I - HRZ w's E-W GOillponent CHI - 11RZ n 54.6!. I I I 1 " " I I ~. I I Zfi.S'l. ~ i M I. I. r~t 1 I I 4.3Y. l ~. 3Jl'J. tu.tj k.=lb=:d!::::=:::i~dh::==:!!-=i!i!liil---~ Fig Distributons of wind differences for time 06

106 -/103- H-S cmponent 43.3'.1. ttrs - 11RZ ~1.6Y. &.Ox 9.1:1. r- 4.6: "1. 8.8'.1. I le.4y. 8.8'1. I tut "' l 3 4 5!itls E=W GOMponent 41.4/. HR8 = rmz 33.3'1. 7.3' '1. ~ 3.1:1. 3.8'1. 2.3'1. 8.-t'l. ' t IUt1. r 8.4:~. J!. l Fig Distributons of wind differences for time 06

107 COMPARISON AT STANDARD PRESSURE LEVELS It was written above that three different types of data were received. Data from synchronized sampling of radiosonde observations, firstly, characterize the instrumental performance and, secondly, provide the maximum quantity of the data for statistical analysis. In addition the data reported at standard pressure levels were also recorded on diskettes. These data characterize the compatibility of different radiosondes readings on the isobaric levels. These are mostly of interest for synopticians. They indicate the overall result of the combination of the differences between systems, found in section 5. Figures show the results of statistical analysis of geopotential heights and temperature differences on standard pressure levels. MRS data were included only into night flights group. For other launch times there was not eno~~ data from this sonde. It should be noted that in the troposphere the results obtained are certainly satisfactory to V'vM:O accuracy requiremer.::bs.

108 -105- Cons. differences of Geopotential Time 18 P, hpa A 10 r l <.I r 141 r r.,/,.. 1 J.\ fy ~ r..., t>f:-.. r r\~_: 1 : r K ; : " -r<y r 1 :,:,:~ r 1! \.! i 1.!!!!' ~... r ~ /!. I! '\!!\!!!!\l~\v!!... r rt :.. T r l T'~ r..:.. :.. r " ~... ~... f'..,"' ~... ~... '!'C?. '!"".~... ~. "'?.:. t~!'... ~" '.!'!". '1"" ~... I l : ~ \~. ~ ~ ~ l 1 ~ ~ f\ J t l,/ ; ~ i 32 1" :... r : ~.,: r wij T r '\!/' i I ;fy~t : r !... '!'.. ~ ~... 'A:."!? t ''!' j rf,.,..._.,.~.. ~.. j..! I...!,...!,......!,!...!,..\J ""tf...!,...! t: li// r ' "... i/!,"'...,...!,...,!..., i... i I l!! 1'\! l ;I; 1 A : i i! 140 I..! t ~.. ~..! "!'"t' "t.. ~ "t' 1'7'1 ~ T!.. t.. ~ j! I!' i i i!\ \: \f\ 1 1l!l! '!: i I :. : : : : I : : I :.I : I :.. : : 200',.. r.. r :.. r r -rrr.. :rrrrrrr... r... T.. r.. r ~.1 I U I '~' t \\ r :f >~J...,... r l J l \ r l l :! ~ l \ fl l~ll! I! J! 7001!...! I. j '!'.. \.. ~ rl f<j.. r... t... [. l.j...!... I,,,,,,, Ji,!J,,,,,,, : ~:.! : Jl B. ~ ~! 2 4! 6!* FIN!J - AIR. V - CHI " - MRS ! lis Sli FIN AIR CHI MRG MRZ USA ) u ll'il ' MRZ lis ss. 21i Sli ( ll ii & lli 19 ~:.- USA Fig. 6.1 Stand. levels height comparison, nighttime (gpm).

109 -106- Stand.deviations of Geopotential Time 18 P, hpa 10 rr... ' r,...!"lj-'.. 7, '!'o~_...!...!"...,_,.... :... ~~~~- :.._:~:..:..._:..:..:J:J i '1. ' ~"'-!--. : ~...r:::._...; l 14 t i, Jt~~~l~Ff~r... r : 20 "' ~ -~.. r.. r:.. :.P>._. ~-... :..!.....:... -~ 11 : _... ~--- -r \ :../~:::t> : : : : ; 32 jii"'""'""''t'''"f"""''"n ~ l...,.,......,...,...,... -; I l :, ///~/. :.. 50 w ~ r ~r yp j :+! -~ : ~ ; -~- n ~t :1 1 ~/~/; ~ fl! l / I /! : : 701\''"""; t )qf";'"!"... j... ; ' I 1 '. l./ './ I../r.;, l '. i ; r : 100 ftl'. y f"'i?'' (>. : ;... I, '.!... '... 'j.. '... '. ~-. '... 11!I/ Y : / : : 140 ~... :i/.!l_ --~-'.L... :.-... ',: :/r!/' :T : : -~...,...!...( '"!""" 11 ~ l/!/ : :.. :.. 200~ tff J t l! r l I, 32011''... ffl'' 'f :.. '' -- :... :... '.!... '. :...!... :... ' : ill /i! : : : :. [ : 1':00 fti"'!p-"!'7'f...,...,... ;.!.,...,...,... I :... ~ ' ;J 11/// l! : w-rlr- A...!....., !....,..... :,,,...:::.....:: Il... ~., t : :! :,1_ 1\ I ' ' './ :! : fl""'". I 2 - FIN Cl 4 AIR " - CHI 8 * 10 l. T- MHS FIN AIR CH I 0. 9li s S? lll ll lil fil, 18. lll u u ' Cil. li M:RS M:RZ USA lis. lili. 2li. 9 lli lli 17 lfl. as ), as u ll. 25. lll ll e IJ lli 19 A - USA Fig. 6.1a Standard deviations.

110 -107- Cons. differences of Geopotential Time 06 P, hpa. FIN AIR CHI MRS MRZ USA.i -82. ::rmr.~~~' IIJm+p 3 2,....,. l r r r.,. l\,. r Jl 1. yp r r r 1 ::If! I II l ' Nf!L i j! I r ~::it r r : I : I j f] ~ i r r I H. n 'l u ls ls Ill ls u /J ls lli ( lli lli l p... ~... ~... j.. ~... "!"... ~... "!".. ~. "l\" "!"..!... "!"... ~.. ~... "!"... ~.... Ill Ill "!\:.., 3201 :+ j :. L l! : T r r T r 1 -:- -r -r trr 1 r r r r 1 7oolf j r ;.! 1 : ~ 'f j : r 1 ~ j : 1':01: 'lijr i FIN l. -1. li. lb ls ( Ill. Ill ( 16 s lfi lot lli *' 10 1 [] V AIR CHI MRS.. - MRZ 1:. - USA Fig Stand. levels height comparison, daytime (gpm}.

111 Stand.deviations of Geopotential Tirne 06 P, hpa FIN AIR. CHI t"..r.s MR.Z USA.i 700 ~...i>i w,...,...,...,......,...,...,...,...,...,...,... t :,., : : : : : : : : : ; : ~ 850~1ll.l j ~.a.,-. ~-- l.. l!! : ~ L? m "' 16 "' 18 "' e e. 16 1/J "' l!l "' 16 "' 0. I ~ ~ ~ i0 ~ * 10 - FIN 0 - AIR V - CHI 'If - :t'lrs lil l!l! , 8 " S ls ls lli. 18 IJ S A - HRZ li7. S4.. e 1e 11 "' as lll lli 21. U> lli lli e lli Ui ll ! u 14 A - USA Fig. 6.2a Standard deviations.

112 -{0.9- Cons, differences of Geopotenti~l Time 00 P, hpa FIN AIR CH I t1'rs HHZ USA! 10 r <.. ~.:_; V ~t~~.~ ~r.2~~1= r r r i 141 [:(;1:/r f\t~:\ : : r, 7 r r '\ r r r v-:..;..:.. I ~/ \ ~1 ~ ~ \; l ~ ~ \\. 32 i K> f p- l! ~! : l 1 i P Jl ~ ~ n ~ ~ :.., I ;! I / ~ ; i P i ' i I 50 I... "tt ~ ~... ~... '!..... ~..... ~ :.. 1 -r I i\ i\ ~ ~ i li ' i i l I '\ i\i ~ i Ji, i i I 7 01".. "l ~ p ~ ~... ~.'.. '.. :. '.' 'J'' :... ":... "''. 'i'".. '. "_L:;,V.. ' I i l~. \ i i /! l --! l 100,... : 1 \ r r.. :,r.. r.... ::.>y-.. r... :.. I : I \I! : ; i ; X : ; 140j"'"'!'l' ~ '''"'j'''''''"tt"''''('.:..:fl''""'"i'''''"''i''"'" I i I \ I / i ' : 1 r.; r -n :;r r r l 320l.j ~ t~~: l r l I ~J I.// l i \\ 1 1 i \ i! : / i i i i.,. '. I. r !... "l". ~. 'f'... '1'.. ~. 'l)!". '! ;:;... "i"... 'i"... ~... 'l'..... I ' \ \ \ i,i,v ' i i i I. \ l \ i I /i i : i a *'.. <t. n r.! :..... :... :... l.... I i i\ \ ~ I t. i ' : i I '\ I 'I ' ' :.i-~j -'!-=-~i--""'!"'--~--!'--=p I : 1. Ill li ll li lis lll li li. -lli ] l s IL ~1 i 3 5 * - FIN AIR V - CHI., - MRS A - MRZ A - USA Fig. 6.:3 Stand. levels height comparison, morning time (gpm)

113 Stand.deviations of Geopotential Time 00 P, hpa FIN AIR CHI MRB MRZ USA A 10 ~-- r ~::.~~~~~L~---~--. T 1 Y"-~F~~-J~ - r \\ r 14 1t ~v y c;? kj 20 r : : :?~- : /'' : :....?... ~.. -~-.. )fo. 11 ~ : : ~~ :_,... : ; /~. :.-----~ 11 : ~ : l:./. :,/.. )---- : 32 [... T... -r... ~... -~:.. ~<~/-~... -~- -~-->r.. t~>f _a ~... : '"...:...:... ~... _r.' '?".. ~... :7 '"[;.:.t..'.. ~--... ~-... ~--...,... 11:: ~/~1:./.~-----, ~ ~:: li : : : / :,t ~ /_...;.--- : : : : 70 ir r -r > r /c~:_:.rr~ -: --~ - r ; 100,....,,... ~.. 'fl"'~... p;f'... -~~. '. ~:... ~"... '1,... ~-."" 1,'... -~ : ; il I / 1 l.. ---\"' :. ; 40 1\'' '~ ' ~ 0 o\ ~ ~ ~ ~ 0 00 ~ 11: ~~,.l-'-t)/i::: n ~ i.. ~... u.. /~ ~ : : f")00 If"...,... :A" ;.. "!;l '7.., 0 0 ~ 'i'... ~... '... '... :_:... ~,... ~,-...,... t.. 11 ~ /1//.l i : 3 20 ~-... _.{ :)~{:_.:V., f : j ;. ;. ~- -~- 11 : \../ i l,/ : : 500 r,a--...,.. r..,.ff-...,.... -~... --~...,...!...!...,...,...,.. li :.f,f : 11 :; -l' : 700 r----l~7 ~ -~--... ;... t--...,...!... -:... --~ u : :,...,...,.. 850j~'"' 0. i : : !3. 12 I'J * 10 11! FIN a - AIR CHI ~ - MRS t.!i 19. li 19. li 21. li li 17. li 111. li 12. li.t Ji 8. 5 lis ss lis. 28. li Ul 11 " li " B. B. li MRZ A - USA Fig. 6.3a Standard deviations.

114 Cons. differences of Geopotential Time 12 P, hpa FIN A. IR CH I HRS t-'irz USA 10t:f~ ~~ru r r f""<4jl ijtj 1. 4 ll. r.,. r l -r r l<~~~-~-1 1.,. r ~\ ry 1 r ::1r i J Ir I r r l Iftf Nl;\~ I 5011 :.. i.. : '.. f.. > : r :.. '...!..!\ n~ : ~... r. i... l:illilt L I~~~~~ i ~ ~ i ~ i: ~ illlv! i i ~ ' r rrt! <Hl~IT r 140 L r ~- ~-! : r ~-! ;? ~ 1! 1 'N r ~ ~! i ; ico~ ; ; I,.,, :.g i 3 - FIN 0 - AIR CHI " - MRS -25. ll!l li li s l. u u. 9 s s " " " IL u " " " li. l!l " " 1. l!l. li li l!l " " " " l!l li -li li -' "... - MRZ 1:>. - USA li. lli I!. lli --t ! -2. lli lfj Fig. 6.4 Stand. levels height comparison, evening time (gpm}

115 Stand. deviations of Geopotential Time 12. P~ hpa FIN AIR CHI H:RS MRZ USA i. T~~~~~~i;O~)-*~r-~~L~~F:_~r 10 w r T -r -r r 14f T 1 'tj~::,;l)7!frr, ::rr rriffl~r rr rrr 50~ - l { l ~< *~~--f- -!- l -l Jl....\ t< { t! - l Jti r 1 j_ I 1- f [ I.!. 100 [ I I Jr~1 :. I -t- 1 - t t --1- r -! -r tj 140 [ - f - f /!- -f f l -! I! : - I ---! If ~ UfJ ~ ~ ~ ~ ~ f ~. ~ ~ ~ :: t J J!A I ri r I J r r I I :::rf1 J Ill I L 11 L 11 If I>N ~ 850~"' t I * FIN c - AIR V - CHI T - MRS Ill. 11!1 1!1. u 1! ! lif Ill la Ill " ( g 8 UJ " 19. u !1 11 " 2!. as. llll S-l. 7 8 " !1-. '{ 8 11!1-12 " 2& ! " u ll ' 8 12 u " " : UL 1&. 13. & 8 Ill Ut. 18. u ' 18 " 7. 11! " &. 'l &. 2: 8 fij _- MRZ A - USA Fig. 6.4a Standard deviations.

116 -113- Cons. differences of Temperature Time 18 P, hpa.i 10 r<-r~-~~-+~~~: r;.. >-t;~j r - r 1 r : 17 i!e 141 \~... j...[... <f [r:{.. --T>~_.-\...;...[...\...;l... 1.ee 18 I 1 '"--,_..J! 1'----~\J \_!.,_\! 1! i _/_./! ~- r<-<j r_>>t~-r+-~~~j r -r ~~-:.. >T.,. i:e 32 1 ~. ~ 'i' '1'...:.. ~ 17 -:_ ~ t-:.:..:.!... I!'.. ~.!..6e I :! I :-...! ---.;!\ -~--.L.. I :! 19!!! "'--.!! ! \! -...-,_1! :.. r.. T<<L '7.:_+~l-r t-.:,... r :.. 1::1! rsrr.. r --z.. [J;+t~r r... Q:... I...,...,.. '7A'C'I''..,... I ,...,... "'!-..., \ \ I \ : -... \ \.h -~--! [ I!! I!!'--...!..J?":- < ! " :.. l. I!!... \,~\... r.. /r ~~t~~t~~~i;j... t r -r r.. r.,..:... --r "\lj_3~~r... : --~<J ll..,. r;r -r 17 1 I!!! I!! I :!.;..-.:.q :! -... _! 500,..,. r 700,. : r r r r-,: -~-- - I.... \.. r r 1 --~-~:.. f-;6) ! -r.....,... i !,, 1 "", +', y, r, ".se I! ~ 8! ~ 4 : ~! 4 : ~ i 10-i 9. - FIN c - AIR 17 I.. ~ - CHI " MRS FIN AIR CHI MRB MRZ USA B !10 19.(0 19.ell u e /J l 1;, - -l.lle :ze e e -l.ell 16 6 lll 18 -.le e ( se Ul !ill se ( lie !Ill.90.se ( (B ( fvlrz 1:. - USA Fig. 6.5 Stand. levels temperature comparison, nighttime (dgs}.

117 --111f- Stand.devia.tions of Temperature Time 18 FIN AIR CHI MRS MRZ USA.eiJ e 11.se I! 1.10 l. 3e ee 1. ee e e li lli e se 17.8e 8.80.'le ee.60' lie ! e 'T.70. 5e ee.80 1& "" 17 '".l!e 11.lie & e '" "".3e se B.40 a l'l 111.8e e l'l ( FIN 4 Cl 6 8 AIR V - CHI 14, "" 1 16 * 10-~ MRS e 17 fv1rz 3111 B.50 8 A USA Fig. 6. 5e. Standard deviations.

118 -115- Cons. differences of Temperature Time 06 P, hpa FIN AIR CHI MRB HRZ UBA r -r r 10 }:.:.~:~~<-l_,.r rt r L~~~~~~:_~t;O 14 I t.>-t-:{:;1 r I! l ~~~:~~~~~r l.,. I i : /\H : i. n \i 201 r! v.:.. ~.. : : r t"r p: ~... : : I :! \\!\\!!! /!//! : i i T\ \~~J~. - l r/~-~\. - : r r l 50!'.. r...!"' T'<-< r-..:"':.. r r.. rr :... r :...:.. I l.\j \ \! / l l i 70 r T r -r... r-<::::'j :r r v 1 r r r -l.lll 13 -l.llll l 18 -.Biil il l l -2.1lll l.lll 11l 9 ll 11l l -l.lll l l.llll ll l -1. Sll -l.llll.91l ll 14 u l ll 14 lli !ill i : T )f v1.. I, 140 1" ""1" : -r lr ~>r.. r!!...!.. r.. r I:. :/ i~/! I'. : : 2001 r! ~- " -~: :~.: t ~r!!,.. : : I : i i -~~-----\ I \i I i i i i -..:-8 ~ r ; 1 r _:A r r! ~..,..,. I i. /H\ f i.. 500,... -~...!.... ~....:. «:r-: 'M pr.. r...!... ~...:... : I : i i i '!.! I \ I i : : : I i :.. I\! \J : i ?...!... ~... : :Y~'I! ~!.. r....!...!.... : : I l ~ j ~ l ~\\; \ l l i i I i\1 I i 6501 A~~~-:--~~--~~~-9 -i5-5 5 i5 25 * 10-~ -.llil 16 - FIN Cl AIR V - CHI "' - MRS A..lilli!l 18.llli!l 18.lllil 18.lll 18.11il 16.21l ll 16 11i.fill l ll ll (/J !ill.ll0.1111l il il lij Siil,(/JiiJ.31l -.llil lij 14 lli il lij 13 ll MRZ.:;_ - USA Fig. 6.6 Stand. levels temperature comparison, daytime (dgs).

119 -116- Stand.deviations of Temperature Time 06 P~ hpa J 10 r,.. --~... -r... r... t... r... :.. -~I~~~-~)-~... J>>". f,.. I : :. :,_- : _.,.,.. : I.-: 141!''.. "!.....,... ~-... -~::r~-.. i... :.).~-:-~.. ;... ).:;..:.:..~y:~<~. (.... u r l l : c:::t~~~::-_:-~----r l J 20 r.,... ~- -~... :..?... 'f;;. -~..:...:.:}... t... t... :.. _:.:y-. 32 r- ~--.. :.. : H j l j j j -.. \..,_i :----t---1-=.c.: (- j t...,.. r<.~ :r.>:t;~~~~: n ~ ~.. i..::=-~- f_../ ~ =.. r... 50"'... '[".. :... ~-... '!".. :... ;.t~..:.:.~4" _:..~'!'". "(... :... ~"... " ~! : : l,l?.~~r_ :..., r.. T ~- )f )1' -;-;-r<-~~~_j i... li t. j' ~,/ ~/ ~ ~ -~-~-:.. 100~.. r :... r<_~ t<.:,~.-r-<.:.:r I~F-~..:~ -.. r.. :... f... -r... T.._>t)t:> :... T...Jf : ~ "-:-... ~ -.\; -~-- l ~ ~ ~ T... '!... '!'... :... Jl ~ : :,i.-~1'' i : : : ft t...'l'... r-:.~-~{;:r~-~:,... l,... '1'... r... r... '!' ,.. ". ~"...:... 'f....~... p. "'t.:... :... ~-... ''!... :. ". -~.... u:: j_,j" :/ : 5f21tZ!l.;..... j..j< ::._i~. : -.. _:::::.j...!._)t ~- -~.j... (.. H l t// l l :~~t---.:1=----l~ l l l ~ 700 [ r-<< J.. -. r<;j... l... l.. :>ff... r... r-..., ,. '? 'i' + -"".. 0 FIN AIR CHI MRS MRZ USA -"" 1.1/JI/J 13 11/J.1/JI/J 1.1/JI/J /JI/J.61/J "" 1.01/J /J.se /JI/J.61/J' /Je.51/J ee.61/J /JI/J.31/J ee /J 16 -"" 18.1/JI/J f : : 16 " 2 FIN * 10-l. AIR. CHI MRS 1.21/J 1.S0 l.sij " 1. 0S.41/J Ill liil /J :8.71/J 13 1/J /J /J 13 8 IS /J /J.41/J.31/J 13 Ill /J /J Ill g 111 lli MRZ A - USA Fig. 6. 6a. Standard deviations.

120 -117- Cons. differences of Temperature Time 00 P, hpa FIN' AIR CHI HRB HRZ USA !1l.41/J lil 11/J /J 11.41/J /J /J.21/J Ill /li/J 11.0/il 11.1/li/J 11.1/Jfll /J 6 -. ll'j 5 " " fllfll !1l.lillll /il.01/l Ill S!Il 12.21/l 7 -.2/il 7 1.1fll 6.60 s ".11/l -.2!1l Sill /il s /l /l /il 1/J /J B. ll'l -.41/J 1/J /il /J 7.6!1l 6.!lllll -.Sill 1/J /J 7.61/l /J -.31/J Ill FIN a - AIR CHI.4!1l 12 * 10-l T - MRS.. -.4!1l 6 MRZ -.11/l -.41/J A - USA Fig Stand. levels temperature comparison, morning (dgs).

121 Stand.deviations of Temperature Time 00 P, hpa! ~:l, ~ nlltl~ltttrtr 3 2 fl. r l~/~:~:f-;:~j r -r<r~_.j l l! ~! 1 r 50[. r r g;<~j LJir r 1 t,:.. > r l r. ~ : :.. 70 rr r r :.l: T<J<f~-~~L~-;.:.:-:r r r r : r : r r ~::ti.i tljf:tfrt i I t. 1 t, J J 200~ I! ~H13> L! ' ; i i : i : +! :::1rm~r! 700 rr..., rrr1 1 t1 l...,.. l.. '!!:;.,..., =.,...,...,...,...,...,...,...,...,..., ~!. ~ :'\~,\.\! l! ; ' :. ' i :! I : : : : ' : : ' : : : : : i0 iz i4. 6. ia * FIN AIR "' - CHI "- MRS FIN.AIR CHI ( s ( !! li se 12 8 G H!:l-~ "' MRZ 1-'JRS MRZ USA " /J ee u u 12 A SiiJ USA Fig. 6.7a Standard deviations.

122 -119- Cons. difference of Temperature Time 12 P, hpa A 10 ~~~~f~~~~~~~l~~-l :<~r~~~~[...'ll... r... Jr-~->~. 14 l : : r.\ r r.-.< :r 1 C(<L\: I ~ ~ ~l, ~ ~ \.] ~ \'li 201'" "!... 'i'... "' ~''\"... :.. "".'!'... t:..""." i'.. "'t.lf.. ".... I! l l \,!! y --,~, l./1' -..\ v:.~-~~j... r... :~\...\r.... t r 3 2 1""'.. :... :... r I ' ' ',... ' ' \ ' ' J ' I 501"' ":... j.. "."..;... + I i ' ~ : -.,_! : \ ~/i ~ \ I ~ ~ : > -.. \ ~/ / : l, 70 1". -:-... T... r 'l'.....-~;;.<.. f... :.. ~... j :/>.f'. -\. q-""..... r. """ T v<<.j'.. ~<:f:~("" r.:..>f.. " ~::1 1 I I T I [1!)1 I~ ~ : ~ ~ ~ll~\l,lj I ~. ~ ~ ~l.ll\ll ~ 2001'.. "!. 'i"... ~... ~..,...,. '!...!. V.. f'.. i', t;.,. :., ' ' ' ' ' r ' 1 ' ' 3201'''. I... :.!... -!. f.... i.. } :,ll~.;.>)...! ~ ~ : :. ~~ :1\.1: 5001 : 1 r r : : \.. 1.'\.ltr I i ~ ~ ~ i \ i ~~\~~ t...!... r... -:-... :... l...\.1..~l~ r ll -.1) '!" ; =l..f-1~. -+ I i -25 -i5 ~5 5 * 10-l. ill - FIN Cl - AIR V - CHI V- MRS A FIN AIR. CHI MRS H'R.Z USA.00 lll.10 lll.20 ls.20 1S.30 lll lll lifll " Lil l2 " " S " se.1) Ill lf) tij ! lli !l " - MRZ A - USA l lll i -.20 lli Fig, 6.8 Stand. levels temperature comparison, evening (dgsj.

123 -'120 Stand. de'.fi.9.tions of Temperature Time 12 P, hpa FIN AIR CHI MRB MRZ USA.f/11/J HI 2.311l li l l 1.611l Ill 8 111l.011l Bill 7 1. Sill B.911l.Sill l!lll Siil Ill J 12.Sill Sill.Sill llllll Sill ''!'''' ltil.611l lllf/J !\Ill l :-- : : :... ;..... ~.....!.11l Siil = : = B Ill :- : :--..;... [ !ii1J.60 lil : : - : S FIN : - --: "!'.llllll 13.lllrll a.31' Sill * 10-l AIR V - CHI MRS A - MRZ i:. - USA Fig. 6.8a Standard deviations.

124 ANALYSIS OF TEMP MESSAGES The aerological TEMP messages are the main means of exchange of operational information between countries using the Global Telecommunication System (GTS). That is why the Organizing Committee decided to include operational TEMP coded messages in the considerations of Phase III. The message characterize the suitability of the radiosounding system for operational work. They also indicate the adequacy of the data processing and the ability of the system to exercise quality control, which is defined by the number of rough errors in a telegram. 9E~E~~!~~~!---~~E~~!!!~~ It was agreed participants that TEMP messages had to be delivered between to the management team during the period of one day just after each the data time of flight. Mainly, all participants fulfilled this requirements, besides Chinese team which sometimes delayed the TEMP presentation. At the same time it should be noted that some TEMP messages were not presented although other data were obtained. The following numbers of messages were absent: FIN - 2 (3 %); USA- (1.5 %); MRZ- 2 (3 %); MRS- 4 (11 %); AIR- 18 (36 %); SMG - 2 ( 4 % ) ; SMT - ( 1 1 % ) ~~E~~~-~EE~E~ The collection and further archiving of the radiosounding information is mostly performed at the large Data Centres directly from GTS channels. Therefore the exactness of the standard formats and completeness of telegrams are very important. Obviously, the optimum presentation of data is required in TEMP messages. The most accurate and complete format FM.36E TEMP code is peculiar to Finnish telegrams. the original radiosonde observance of All indicator groups are presented and all groups of data recommended by WMO are included. The MRZ messages were rather satisfactory and there were onl~ a few of flights where tropopause data were absent. The checking of MRS messages (OKTAVA software) revealed the absence of second tropopause data when two tropopauses were observed. That defect was confirmed by the authors of the software. OKTAVA includes into TEMP message only one tropopause and first one as a rule. The tropopause data were absent in all USA telegrams however these data were found between significant levels of Part B.

125 But this deficiancy exists only in Dzhambul's data and is not characteristic of operational US data. AIR TEMP messages contained sometime seven symbols in group instead of five that is obviously a result of some software confusions. The indicator group is absent in Part B. Most of the numbers of deviations from standard formats observed in Chinese telegrams. Three different printing forms presentation were produced and many declinations from standard format were noted. The one peculiarity was of cleared that usually significant levels of wind profiles be never included into Parts B and D. It is not foreseen by Chinese Handbook. In addition, we checked the content of telegrams with the purpose to find some rough errors. There were no rough miscalculations in FIN and USA messages. There were a small number (4 points in temperature and 7 ones in geopotential) in MRZ messages. As for the others, rather many uncertainties were revealed in AIR and MRS (more than 20 in ge~potential). It was probably due to bad conditions of signal propagation, that caused some difficulties during first processing. Chinese messages contained 6 telegrams with 15 wrong points in geopotential and 12 telegrams with 33 wrong points in temperature. Later on these errors were corrected. Mean differences between telegrames data were not calculated but some graphic presentation of these data might be interesting. Figures 7.1 and 7.2 show how the geopotentials and temperatures at some standard levels varied with time. The deviation of 0 temperature are within the range of 1-2 C at 100 hpa but above km that range increases up to 4-5 C. For geopotential those ranges are m below 100 hpa and m above The wind data of messages are example, wind speed at the m/s and direction of this level. rather satisfactory. Thus, hpa coincide within range The data of significant levels are of great interest because namely those are used for reconstruction of measured profiles. But it was not possible to average these data for objective conclusion. Therefore, we analyzed the most for of important parameter, i.e. tropopause. Data of pressure and temperature at the

126 tropopause levels are given on the figures One can see that scattering of the data is in the range of hpa for 0 pressure and 2-3 C for temperature. At the same time the divergence of first tropopause data is much larger than of the second one. However, there were particular flights (numbers 18, 35, 62 and 65) with wonderful coincidance of all radiosondes readings for tropopause. Figures 7.5 and 7.6 show some fragments of profiles constructed from two kinds of data of radiosondes, i.e. TEMP messages data and minute smoothing of AVK software is evident. data. temperature different The large

127 ... '1 0 gpa t' oc r A V I V V'~~ ~'f61! ~ '-/ -,,- "o ~/ I 0 Q......_..,..._ -3 5 r A ~ " : ~ 0 )( 0 X J( f gpa x -50 f ~>..a.~ A u:. o u': 0 0 I 0-45 L. ~ t ~ y 100 gpa J IA~lr~ ~AA., ~ - A.J."'O I '\:. A ~ A Fig. 7.1 ' N of flight Time variations of air temperatures (from T~~ data). - FIN A lvirz Jlf.LRS X CHI ---USA o AIR

128 H km ~2.0r..o. A I - " 10 gpa 25:1 30 gpa. 24. ~ I J\ o-.4. \ 24.Q- - - Q ~ <.J, I N of flight Fig. 7.2 Time variations of geopotential heights (from TEMP data). - FIN 6 MRZ 1v'IRS x CHI ---USA o AIR

129 -o gpa... ' * * ~ <>.. X.tax } ~ 0\ I 200 ~ i 0 t 3001 A A~A 10 X )(a~! a<> AA Ill [] l( A A 8 28 Ob c A 4 50 t-s. Ao9a 0 60 A Bit N of flight Fig. 7.3 Time variations of tropopauses heights. D- FIN A 11ffiZ ThrRS )(' CHI <>---USA OAIR

130 t, C -65 t )( ~ X X X<;>'lf. a oo0.=. A 111 ls b 10 X 8 A~ ~ "".t\ 8 A A X 8 A t ~ b.o 60 N of flight I ~ ~ 1 Fig. 7.4 Time variations of tropopauses temperatures. CJ- FIN A MRZ l'j1rs X CHI<>--USA oair

131 P ~ ' hpa a) b) I ~ ~ I t' C Fig. 7.5 Fragments of temperatures profiles constructed from TEMP messages (a) and minute (b) data. --FIN --- MRZ - -CHI -K-USA AIR t, C

132 P, b.pa b) 1 ~ t' C t, C Fig. 7.6 Fragments of temperatures profiles constructed from TEMP messages (a) and minute (b) data. -- FIN -- -MRZ - -CHI -x-us.a 'AIR

133 -1:)0-8. CONCLUSIONS 1. Phase III of the WMO International Radiosonde Intercomparison was carried out in August 1989 at the upper-air station Dzhambul (USSR, South Khazakhstan). Data on the compatibility of USSR, China and AIR Inc. radiosondes relative to two link radiosondes of Phases I and II, i.e. Finnish and USA, have been obtained for the first time. obtained: 2. The following results for main parameters have been 2.1. Observed differences between simultaneous temperature radiosonde measurements, i.e. between RS80 (FIN) and MRZ, MRS. SMA-GZZ (SMG) and AIR, were within the range of 0,5 C 0 and in many cases 0,1-0,2 C, in the layers below 50 hpa. At levels 0 above 30 hpa mean biases increased up to 1,0-2,0 C The simultaneous geopotential heights differences between the Finnish radiosonde and both the Soviet and Chinese ones are small. They do not exceed gpm below 100 hpa and increase up to gpm at the 10 hpa level at night and up to 600 gpm (SMA-GZZ only) at daytime. Significant divergence (more than 600 gpm) of AIR radiosonde at very high levels was observed. This was obviously the result of systematic bias in the AIR pressure at high levels. In particular ascents large deviations of radar system heights occured at low levels (below 500 hpa). This was caused by short durations of radiosonde signal losses by the tracking equipment in unfavourable surface wind conditions The pressure differences corresponded to the differences in geopotential height. The range of values indicated by different systems was 2-3 hpa at 500 hpa decreasing to hpa at high levels. It was noticed that pressure sensors were better at low levels, but radar method was more reliable in high atmosphere. 3, The reproducibility of the tempera. tuj.~e a.nd calculated from Intercomparison results of the standard pressure deviation

134 value and reproruacibility of Finnish radiosonde seemed to be slightly better than was estimated in earlier phases. The better quality data of AVK~MRZ system compered to the older Meteorit-MRS should be noted. It is observed both in mean biases and in reproducibility and may be explained by better reliability of new radar and telemetry. 4. The mean differences in the temperature and pressure observations of link radiosondes, i.e. Finl&Ld and USA, in Phase III were larger than in previous phases. Some investigations and tests should be organized, in particular special studies of infra-red radiation influence. 5. The wind measurements proved to be rather good. It should be outlined that three different systems, i.e. radar, radiotheodolite and Navaid ones, were tested in Dzhambul. On the whole for all participating systems 50% of differences did not exceed 1 m/s and 80% - 2 m/s. An increase of differences was observed in some difficult situations such as very low or very high elevations, losses of radiosonde signals and screening by local objects. As a result of this comparison, good possibilities of all systems for wind measurements may be noted if there is no preventive factors. 6. The humidity measurement results of the radiosondes with different sensor types seem to be close to expected. Three types of sensors were used, i.e. gold-beater's skin with rheostat (SMG, MRS, MRZ), carbon hygristor and thin film capacitor. The differences between time constants of response are very clearly observed, especially for inertial sensors of first type. addi tion, ~hese sensors have extremely slow responce at a 0 temperature of -40 C. It is evident that the goldbeater's skin sensors are unfit for the detailed investigations of humidity profiles at very low temperatures. Average differences of readings within the range from 20 to 80 % at temperatures up to -30 C correspond to permissible errors of -5 %. In

135 The analysis of TEMP messages have demonstrated that fully automated systems provide better quality of telegrams (standard format and completeness) than semi-automated ones. Those are Finnish system, in first turn, and the Soviet AVK-MRZ, in second. Due to software defects the data of second tropopause do not hit in the TEMP messages of "Meteorit-MRS" system. Obviously, the AIR system software was still under development and some errors in telegrams were found. Chinese team had some difficulties in preparing messages in field conditions. Nevertheless, all participants understand the importance of keeping up good quality of TEMP messages because it is the only way to transmit radiosondes information through GTS. All above mentioned defects were received as a commision to improve quality of telegrams as soon as possible. 8. The tests of new Chinese radiosonde were not carried out in sufficient volume. But the analysis of the data obtained have shown much better quality of humidity measurements. The additional investigations and tests of the interference problem are suggested to be performed. 9. Estimating the qualj.ty of the Intercomparison results and applying them to the data of operational sounding in the USSR and China one should bear in mind the differences between the length of suspension. China and the USSR use a radiosonde suspension of about m in operational measurements whereas in Dzhambul the radiosondes were suspended at least 30 m below the balloon. Further special tests need to be performed to check that the length of string is enough to avoid the balloon influence at all levels up t;o 10 hp a. 10. All participants were "illlanimous in the opinion that similar intercomparisons of operational radiosondes should be carried out regularly with intervals of 4-5 years.

136 ACKNOWLEDGEMENTS The USSR is very proud to host Phase III of the WMO International Radiosondes Comparison. We thank the WMO Secretariat for giving us an opportunity to organize and carry out this interesting international experiment. An International Organizing Committee (IOC) chaired by Prof. S. Huovila, Finland, was set up by the president of the Commission for Instruments and Methods of Observation for support of the organization of the intercomparison. It gave excellent guidelines for all three stages of the radiosonde comparison, i.e. preparation, implementation and analysis of the results. Further, Dr. E. Sarukhanian and Mr. S. Klemm of the WMO Secretariat provided valuable additional support for carrying out the intercomparison. We express our sincere gratitude to all these experts involved. The Dzhambul experiment would have failed to become Phase III if two reference radiosondes, i.e. Finnish and American ones, did not participate. We are very grateful to the Administration of both countries who made a decision to support this Phase of the WMO Radiosonde Intercomparison. The members of the Kazakh Republic Administration have made great work during the preparation period. Mr. V. Manannikov designed and made a synchronization system for simultaneous sampling of radiosondes signals. Mrs. R. Cherednichenko made the practical preparation of the flight balloons and rigs during the very important early period. All the staff of upper-air station Dzhambul, under the leadership of Mr. V. Ustinov and Mrs. B. Kurdjieva, did their best for the success of the experiment. We thank very much all the guests of our country, who took part in Phase III. In spite of the big differences in the working and living standards between Dzhambul and their home environments, they were very patient and diligent. We hope that a friendship and co-operation between all the participants will be preserved for life. Dr. John Nash, UK, as Data Co-ordinator, made a significant contribution ot the successful realization of this experiment. The final analysis could not be finished without the contributions from all the team leaders participating in the work. They are Prof. Liang Qixian (China, Chinese Academy of Science), Mr. Veijio Antikainen (Finland, Vaisala Oy), Mr. Melvyn Gelman (USA, NOAA, NMC), Dr. John Nash (UK Met. Office) and Dr. Alexandre Balagurov (USSR, Central Aerological Observatory). We thank also Drs. A. Balagurov and G. Trifonov for their help in the preparation of the Report. We hope that the results of Phase III will prove interesting and useful to all scientists in the World, who use radiosondes data. We wish all our colleagues great success in their routine and research work and prosperity to all the Members of the World Meteorological Organization.

137 ,..:. /!:34 :_ REFERENCES 1. Zaichikov P.F. Preliminary resul ts of data analysis of II-nd International Radiosondes Comparison. CAO Proceedings, Iss.22, Moscow, 1957, pp Goltsova K.I., Marfenko O.V., Petrosyants M.A., Reshetov V.D. The intercomparison of the Soviet and American systems for ship radiosounding. "Meteorologia and Gydrologia", 1974, N 12, pp Zaitseva N.A. About the radiosondes intercomparison in GATE experiment. Proceedings of Atlantic Tropical Experiment of Volume I - "Atmosphera", Leningrad, Hydrometeoizdat,. 1976, pp Karhunen P., Trifonov G.P., Yurmanov V.A. The intercomparison of the Soviet radiosonde system "Meteorite-2-MARS-2-0KA-3" with the Finnish system MicroCORA. "Meteorologia and Gydrologia", 1987, N Zaitseva N.A., Ahmetyanov R.K., Karhunen P. On the results of the intercomparison between the Soviet and Finnish radiosondes. ''Meteorologia and Gydrologia", 1989, N 1, PP Nash J., Schmidlin F.J. WMO International Radiosonde Comparison (U.K , USA- 1985). Final Report. WMO CIMO, Report N 30, March 1987, 103 p. 7. Schmidlin F.J. WMO International Radiosonde Intercomparison, Phase II, WMO CIMO, Report N 29, 1988, 113 p. 8. Hooper A.H., Ponting J. Analysis schemes for treating data from radiosonde intercomparisons. International Organizing Committee for Radiosonde Intercomparison Report of first session, Annex I, 1983.

138 9. Anderson T. Introduction into multiple statistic analysis. Moscow, Fizmatgiz, 1963, 500 p. 10. Fridzon M.B. Estimation of temperature and humidity measurement errors at radiosondes on the USSR aerological network. "Meteorologia and Gydrologia", 1989, N 5, pp Kitchen M. Compatibility of Radiosonde Geopotential Measurements. WMO CIMO, Report N 36, 1989, 79 p. 12. Ahnert P.R. Precision and compatibility of National weather service upper-air measurements. Proceedings of 7th Symposium on Meteorological Observations and Instrumentation. American Meteorological Society, New Orleans. pp

139

140 A P P E N D I C E S

141

142 - 1- Appendix A MRZ-3A radiosonde (USSH)

143

144 - 2- AppendiX A. R~S-2 radiosonde (USSR)

145

146 -3- Appendix A SMA-GZZ radiosonde (China)

147

148 - Lr- Appendix A IS-4A radiosonde (AIR)

149

150 - 5- AppendiX A RS80-15N radiosonde (Finland)

151

152 -6- Appendix A VIZ-1392 radiosonde (USA)

153

154 -7- Appendix B Distribution of different systems at Dzhambul site. Om ~""',> r.':") ::...J r,.j C;.J 0 \} 01 C2. C> Oi CV \') 0 0 'l.) \J7 I.S) l~ '.,. v IHR. 8 t-- l _ :1. '=== ~..... ::ru ~ ~ ' ~. '.,--.. ~\ t..:) 1- ~ U.SA MR.S -~ (' u t( FIN D Sn, ~.. ~. r 6 NI/ ~ 75m 1, AVK building 2, Meteorite-2 building 3. Meteorological site 4. Launch site 5. Hydrogen building 6, Chinese radar 7. AIR antennas 8, DigiCOR.A receiving antenna 9. MRS, MRZ, AIR, FIN, USA, CHI are places of ground equipments

155 -8- Appendix C Flight rig configuration 1 1- Chinese radiosonde transponder 2- CHI.3- AIR 4- MRS 5- USA 6- IVJRZ

156 -J- THE SOFTWARE DESCRIPTION Appendix D The special service-reference software for the checking and visual review of simultaneous data set was designed by UK Meteorological office had loaded a powerful IBM PC AT the USSR. computer especially for the purposes of software design and data processing. In accordance with the recommendation of team leaders meeting this software suite named LOOK is briefly described below.. LOOK operates with six specially organised files named FIN.MIN, AIR.MIN etc. Each file contains simultaneous samples from all available flights of Phase III. Firstly, it checks the data at the disk and shows the table of available flights and invitation to choose one for the review. User can select desirable combination of the variables and then configure screen for visual review and checking of variable measured. Unlike previous, the current version of LOOK calculates and includes into data set some extra parameters, such as orthogonal wind coordinates and ascending rate (advised by Dr. J. Nash). can show simultaneously both, the measured value and their differencies (proposal of Mr. V..A.ntikainen). This version allows to assign desired subset of colors from standard IBM EGA setting. Profiles built by the LOOK include only about 40 minute-points per screen (tecnical limitation of EGA video system), so user can scroll data to see any part of a flight. For convinience the standard pressure levels are shown. User can print desirable profiles if Epson-compatible printer is available. materials of this report have been prepared with the help of software. All possible operations are summarised It Some this in the Help screen which is called by pressing F1 key. One new feature was added in current version: by pressing D Delete mode. It allows simple editing function user can switch on/off deleting data from the files. In this mode, it is possible to delete selected point by pressing "DEL". Key ''BackSpace" deletes both pressure and geopotential if one of this pair is currently chosen and does same with the wind parameters. The data base files begin with 72 of 2-bytes integers, first 66 are the number of minutes in each flight and 6 are reserved and added to ajust record length to be equal to 24 throughout all file (for the faster access). the Data of

157 -10- the flights (each minute vector is presented by six 4-bytes floats, impossible value is assigned for missing data) follow this information. A special utility "Manage" was designed to support the data base. It shows current state of the data base, performs export/import with "ASCII" files and some other operations to control data flow for statistic processing software. There were some statistic programs designed to prepare results of comparison. They include implementation of consistent difference method, robust (not very sensitive in a case of bad agreement of the sample distribution with Gauss one) adaptive algorithm and 2-dimensional statistic search. All described programs require IBM-compatible personal computer with MS-DOS 3.30 or higher (were not tested with previous versions) and at least EGA (possible VGA) video system. Total size of simultaneous data base is about 800,000 bytes. Software is written by S. Kurnosenko using Microsoft FORTRAN 4.1 compiler in calculation and data access parts and Microsoft MacroAssembler for service part (user interface and graphics). In future software can be expanded with some other needed functions, adopted to visualize mandatory levels data and equipped with simple installation part to process data regardless of Phase III limitations.

158 - 11- RADIATION CORRECTION PROCEDURES Appendix E E. 1. Radiation Correction for MRZ and MRS radiosond.es Radiation corrections for MRZ and MRS radiosondes are calculated by formula: (E. 1) where h is geopotential height, h 0 is elevation angle of the sun, p is density of standard atmosphere, Ill = v = ( h)/ is rate of radiosonde ascent, (E.2) p(ho) = Ill 1 + d2h0 + d h 2 Coefficients a to d9 are equal to ( ; ; ; ; + Ill -h4 4 0 (E.3) ; ; ; ; 0.33i06) (E.4) 1-cosh 0 h = r cosh 0 (E.5) where r 0 is radius of the Earth. When elevation angle of the sun is negative (less than -5 ) radiation correction is equal to zero. At the angles from -5 to 0 the calculations of radiation correction are made from initial altitudes where radiosonde is insolated. Table E.1.1shows the radiation errors for old radiosondes RKZ which had the same temperature sensor as MRZ and MRS ones.

159 -12- Table E.1.1 Radiation corrections ( C) for RKZ radiosondes temperature sensor p [hpa] s < ' ~

160 -13- E.2. Finnish Radiation Correction for the Temperature Sensor The elevation angle (S) of the sun I, S = arcsin(h) h = sin(lat.)sin(decl.) - cos(lat.)*cos(decl. >*cos(t) t = (time GMT in min/4) + long. decl.= *sin{ *day + 1.8)- 0.1 lat.= latitude of the sounding location long.= longitude of the sounding location By using values for S and ambient pressure (P) just calculated (measured by the sonde), radiation correction (K) can. R be interpolated from Table E.2.1.

161 -#- Table E.2.1 Radiation Corrections ( C) for RS 80 Radiosonde Temperature Sensor P [hpa] s ~ ,

162 -15- E.3. Radiation corrections for SMG radiosonde temperature sensor f I!T =., I (pw)o.698 I * Q * A (pw) ~ ~ AT = * Q * A (pw) < (pw)t.3642 I!T = 0 l Q = tg- 1 (-~-) Hi H H 3 r A = 1 p :5 300 hpa r "l 0-6 i A = I 1 - -~-I I l_ o I I!,.. j p > 300 hpa f gr -1 (pw) ~ = l M 2 Min J 1.02 * i=!el_ih~~j A,- [M in] H solar elevation ( 0 )

163 Table E.3.1 Re,diation corrections for SMG radiosonde temperature sensor p [hpa] s L ? r:: ~.u r,,,;, ?

164 -17- Appendix F THE EQUATION OF THE PRESSURE CALCULATION FOR RADAR RADIOSOUNDING SYSTEMS The Meteorire and AVK systems compute pressure distribution along height from their radar height measurements and the radiosonde (MRS or MRZ) temperature and relative humidity observations. The dependence of the acceleration of gravity on local latitude and station elevation are taken into consideration. The following equation is used: l -g_.fta-~] RT p =ye+ (P 0 -ye)exp- % ' where P 0 - observed station pressure; p - pressure on the upper boundary of the layer considered; e - vapour partial pressure in the layer considered; T - temperature of the layer; R - gaz constant; g~ -gravity acceleration at the latitude~; Ah - geopotential hieght of the layer; r = (ratio of the difference between air density and vapour one to the air density).

165 Appendix G DATA OF THE NEW CHINESE RADIOSONDE SMT It was reported above that China presented two radiosondes for Intercomparison (see part 2). Unfortunately, in practice it was not possible to release both Chinese radiosondes and therefore old one, i.e. SMG, had a priority. At the Chinese ur~ent request ten flights were made with new SMT sonde. But because of above mentioned interferences only 9 ascents were partly successful (due to some gaps in data). Therefore, statistics of SMT differences were not calculated. Figures J.1-J.2 show vertical temperature and humidity profiles of two flights made with the new radiosonde.

166 FLIGHT 59 temperature FIB CHI IIRZ OSA 85 fr 1 :! l L~?;T 1 1 : ~::: :::: il I!!! ~~--_..!! s9.3 -a1.s I!!! v:;;.- r.! ; & -u r : ~ ~ ~~~ l r : ~~E:i~:l~:; 751( "l" ; '! ~:~..;.-v,-~;..:.<>';_:.:a' '( j' oooo ! "loo - -4& li!!! F ~- f! ; :! - -u.0 -u I!!! '\. 4;! t!! a -u.a I!!!..? A t..! : u I!!!!.v..,..;--)--"-!! ;! & ,....,... oo!""""''"""!"'"""'"'"'!''?'"""/ff'~'"''""''''"'!'''"'"'"""'~"''""""'"'!'""'""""''!'' & j _>:V.e:---t 1 j &.8 I!!! v::.= -t~. f!!!!! tu u I!!! )- /~~_.! : I!!!,'<f. f'f! t!... ; -u.s ! a l... :... n.. J>:.,..~ l.. _ 4 s.e -ae.e _ 48 7 _ 47 _ 4 I! : : ---~'3--+~ ;! :! : a 60, I!! V'.P-_:~-!! -ti & : : : r i'f'f : : : :. -u l.a.,. j... j j '!I' j j!! j! ! :,.<l _:.;.ll.:.~.. 0 t ~ , !' : '! j : ~--V~- i i! i i i lj v.::::- ~: j j : j j j Ji! V 'f.!'/"!! '1.4 -lili I!! /..-A.J!'!.!... -5&.4 -&8.1 -au -6u 'l'"\"... l''!t'.. ; : j' '!" j' "!" 'l" ,!" 00 0 : :.~v _.A_,P- : : : :. : : : I! _v, t_:.,. i i i i i i i Sfi.B 'if-':j_ 4f4... j j j j j j j I! _.i.-i'l_...a _.;,\! :! : : ': : : ,... V'''JA',)A,.-:: oo :...!'"OO""''''"!'""'''"'""'!''"'"'"'''"'!' oo.. ; "''""'''""! lj '(" f' 1..-;:, j j j j _,.-;::A~ j j j j j j I! T.tt""-~! :! ' s.1 -su -6u I! 7 ;... P'.!...!.. -s1u -62.& -st !00 'l' ; '! ~;,v _:,;:._;_p :... ioo...!..."l'. -flu _ 88 _ 8 _ 82 3 _ I! '\ )'~! :!!!!.! L-1 ~!! ;! : su V--~-~... : i :!! ' -ss s.c H V~~----'! i! i ! : ,~:..:.t"-+.:..:..:_: : j"... : !.. _ 8 u _ 8 u -su _ 6111 _ 11! -...,,:~-~~..._!! i!!! i fl ! '!'--. ''\'!!!!! i! fl I!! '\ A., "\.!! :!!!! I' : v-... A----~ : : : : : : i''''"''''""''!""''::-,...,.~-:::- ~:.:,:A.-;.,;:"''''''~"'"''"'''"'i" ""''""\""'""""'''j'"'''""'"oo'~'''"''''''''"'! : :..,..._ A-~»- : : : : : : j j -..,--=::::t-":'~ i j j! liu i!! ""7--..,I~-~ i!!! -48.1i liu ,, : : :.., 'IJ,.._"AJ-.._: : : -( f! j ~ ::~..,~~~J"t.t;,;: + j j! -U.II : : : : T! '*... : : : : ~>1- "'..,. j j j j j. 1! v~-..l ~...!!! I!... :v ~-! i I!""'"OO'"""l"'"'"'"'''''!"'''"''''"'''~"'''"''''"''j'""'"7'.o..:..:.:A~.:.:_:.:" ""'j'''"''''""'''!''"'"'"''""!'' !! :!! f"l'-.:.q~!! : : : : : : --.,~~ : : -88.' i i!!!!! -..,.,;::~ i SUI 1!! 0! 0 i 0 : 0! 0 i 0..,-9o~! ;. 1:'>7" *10 " - FIN V - CHI A - HRZ A - OSA Fig. G. :1

167 FLIGHT 59 humidity 30~.... r r... T...;;<..: :..,..._ i '7.. ~ I --t------~:.j. ~----~~-.+ ~ I ~ -~--t---,. ~ i I : I I : I r r.... r.... :...., I :._,.1 ~....,, 251 r?[>+~~ (, ) :.. : ---._ --...;._ ' : -,, I. : ~J7 i -- --~ 4,~/-- I v'!-!!-' ~ 1\ :.: : --, : : }>. 1 l:.-l" / :. -~ -----'"j : 51,. T~~~/r,-!., I : : '.:. TT : : :.. (-~-/ lr~~ / 1,.. r..... fin CIII HRZ OSA l & I I /TV : =-'>~~ : ~ -~: İ 0 :. : A.--~--~--"!----!-----j;lll*lJill 51 1 i t 8 9 u u -m v - CHI il. - MRZ.. - osa ' M 51 Fig. G.2

168 -21- ANALYSIS OF ANGLE DEPENDENCE ON THE RADAR MEASUREMENTS OF ALTITUDE Appendix H To study the dependence of radar or radiotheodolite measurements of geometric radiosonde coordinates on antenna's elevation is very useful because it gives information on the quality of system and antenna device in particular. Such an experiment may be organized by means of simultaneous and synchronized independent measurements of the same parameters by optical, precise radar or barometric methods. We tried to use data of Dzhambul experiment as independent ones. Fig.1 shows the elevation distribution of all minute readings obtained in Dzhambul from AVK printer. The discreteness of angles is 1. The picture shows that in most of cases the radiosondes was performed in rather optimum the tracking of range of elevations from point of view of measurement accuracy and dynamic loading on 0 the tracking system, i.e. range of That was not result of system work but characterize the region and time intercomparison, that is wind condit-ions. Nevertheless, of the it makes possible to estimate the reliability of the results represented on the next figure. Fig.2 shows the dependence between the altitude differences of two systems, i.e. AVK and AIR, and elevations. The angles less than 10 had no good statistics. The clear and monotonously decreasing periodicity of the differences MRZ-AIR with period of 0 6. Is noticeable, that period fully corresponds to width of angle diagram in main lobe and to distance between zero sides of side-lobes. As a result we may with confidence confirm that radar system may enter an additional error into elevation measurement and altitude, correspondingly. The magnitude of depend on stant range of radiosonde, orography and this error will on height of antenna installation. In given case it may reach 100 m at the angle of 12 fluently decreasing to zero close to 40. Large differences of altitudes in the region of were caused probably by failures in tracking system at the beginning of observations at the angles close to zenith. The further experiments and attentive analysis will give in future the possibility to account the errors of radar gauges caused by side-lobes of antenna angles diagram.

169 -22- di~trihutian Step 2 deg~ees Total points: , ;... ' 380 '"'"'"""'~""' ;...,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.'.'.. > t I I I I t 0 I 0 I 0 " < f < 0 I > I I I I I I 0 I I I 0 I I I ; I t I 0 I I I 0 I I T 0 I I 0 I I 0 I I I>~ I 1 I i I f I > 0 0 1> 11 > f t I I t I t.. I I ' ~...!59 '""" ;......;...; Fig f-1 1 AIR - MRZ 100,9 """"' ""I''" "' '''i" ''""'""(""""""'i"""'"'"''i'"""'""":"""""""~'"""""'"~"""""!'tl : : : : : : :. I _:::: - - -/,[ ;J\ ~J~ -~L\ J~ ] 2~ l i'\,. \'I : "" : \ i ' \11 \ : I I f ' V : I \ / VI. I f. '\. { I ~-.~.i/... l i : \,. if ; ; \ : -... ;i I ; :. I : : : : : : I ~ : :...,... -:....J...,... "',j' "'"'f" :...,.... J ; ; ; ; ; : I I ; :,. -1s ,..., ~..... ~ ~..... ~.. 1.j... ~... ; : : : : I : : ' =aoo.e... -:...,... L...)...\...[... 1,./... L...\..... : :. : I I : : Q,... : -399.@ 1 1 Fig R.2... <... : : : : I I : :!... ;:...:: , : : ;- < : u!. :,. 1 I.,... I I

170 -23- APPENDIX I PARTICIPANTS IN PHASE III OF THE WMO INTERNATIONAL RADIOSONDE INTERCOMPARISON Project Management Project Leader Site Manager Flight Directors Data Manager Technical Support Manager A. Ivanov s. Rodionov V. Manannikov R. Cherednichenko N. Zaitseva V. Manannikov USSR Team Leader A. Balagurov V. Ustinov B. Kurdjieva G. Trifonov V. Yakushin s. Kurnosenko N. Palmova G. Plotnikov A. Kats A. Kozin CHINA Team Leader Liang Qixian Dai Tihao Ya Lianghe Hung Binxun Zhou Jihe Su Shouyi Yang Shaolan Fan Zhede Sun Luzhen FINIMJD Team Leader V. Antikainen J. Valle A. Paukkunen H. Turtiainen P. Vikman P. Huttunen J. Mikkola

171 -2.'r- Appendix I USA Team Leader M. Gelman A. Eubanks R. Savage J. Kervin D. Tolzin K. Burkhardt UNITED KINGDOM Team Leader J. Nash T. Oakley D. Call D. Harris

172 -25-