WMO INTERNATIONAL RADIOSONDE COMPARISON

Transcription

1 WORLD METEOROLOGICAL ORGANIZATION INSTRUMENTS AND OBSERVING METHODS R E P R T No. 9 WMO INTERNATIONAL RADIOSONDE COMPARISON WMOffD- No. 7 99

2 FOREWORD The WMO International Radiosonde Comparison, Phase IV, was carried out in Japan, at the Aerological Observatory Tsukuba of the Japan Meteorological Agency from, February to March 99. It was designed to finalize the first series ofwmo radiosonde intercomparisons. The aim of this intercomparison series was to compare the relative performance characteristics of the major radiosonde types used operationally by Meteorological Services. The results of the previous intercomparison Phases I- Ill, at which radiosondes of other WMO Regions have been compared against defined link radiosondes, have already been published in this Instruments and Observing Methods Report series, namely in Reports No. (WMO!TD. No. 7), No. 9 (WMO/TD. No. ), No. (WMO!TD. No. 9) and No. (WMO/TD. No. ). All phases of the of the comparison have been carried out under supervision of International Organizing Committees composed of recognized experts serving in the WMO Commission for Instruments and Methods of Observation (CIMO). I should like to place on record the gratitude of CIMO to the management and the staff of the Japan Meteorological Agency for hosting this comparison, to all those who took part in preparing and carrying out the test in Tsukuba, and to those responsible for the evaluation of the data and preparation of the results. I am very pleased to thank the authors of this report as well the members of the International Organizing Committee for the time and efforts they have devoted to the preparation of such an excellent report on what is a very complex subject. A word of appreciation is also due to all others who so willingly contributed in one way or in another in the preparation of the report. I would also like to highlight that some NMHSs and manufacturers supported this undertaking. 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 radiosonde types have been used in their national networks to obtain the upper-air observations. (Dr. J. Kruus) President of the Commission for Instruments and Methods of Observation

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4 Contents. Introduction.... Radiosondes and systems used in Phase IV.... Overview of participating radiosondes and systems.... Japanese systems.... Finnish systems.... USA systems.... Description of the field test Participants in the Phase IV Preparation of the field test Flight schedule Collection of the comparison data.... Schedule of the comparison test Meteorological condition during the comparison period....7 Achievement of flights Compilation of the final database Method of analysis.... Link radiosonde performance relative to earlier phases.... Comparison of simultaneous measurements.... Temperature.... Pressure Geopotential height.... Relative humidity Wind Results from -thermistor radiosondes Consistent differences Amount of temperature correction Results from simultaneous flights (case study).... Comparison at standard pressure levels.... Temperature.... Geopotential height Analysis of TEMP messages Tropopause level.... Conclusions.... Temperature.... Pressure.... Geopotential height.... Relative humidity.... Wind...:-:-.:.... -thermistor radiosondes....7 Comparison at standard pressure levels.... TEMP messages... Acknowledgements... 7 References...,... Tables... 9 Figures... Appendices: A. B. c. D. E. F. Photographs of radiosondes... Location of antennas... 7 Flight rig configuration... Radiation correction procedures... Recomputed JP wind... List of Participants in the Phase IV... 9

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6 . Introduction Observations of upper-air temperature, humidity and winds with the radiosonde are now performed routinely at about 9 stations in the world. These data are immediately exchanged through the Global Telecommunication System (GTS) and, along with other meteorological data, used at national meteorological services. Upper-air data are also available by other methods, for example, remote-sensing from meteorological satellites. However, the radiosonde observation is still of importance because only this technique is the in-situ method that is used by other techniques as a reference. The radiosonde data are widely used for the numerical weather prediction. As the accuracy of numerical model has steadily improved, demand for more accurate and globally uniform upper-air data has become larger. In addition, as there has been a growing concern about the global warming caused by human activities, studies of the climate change require more globally and temporally uniform upper-air data. At present, various kinds of radiosondes are used in the Global Observing System (GOS) and in some cases radiosondes of different types are used even in one country. Radiosondes are disposable and therefore must be inexpensive, and the measuring ranges should be wide (for example, between + and - C for temperature, between and hpa for pressure). In addition, they may receive direct solar radiation during the ascent. Because of these conditions, a systematic bias is found between observations with radiosondes of different types. Therefore it is important to investigate the systematic differences by intercomparing the radiosondes used in GOS and to utilize the comparison results for the improvement of the instruments and observing methods. The comparison results are also useful for users of the radiosonde data. In this context, the field comparison test under the same condition as the routine observation should be carried out as well as laboratory comparisons. The World Meteorological Organization (WMO) decided to conduct comprehensive intercomparisons of radiosondes used in GOS and performed three phases of comparison test (Phase I: in the United Kingdom in 9, Phase II: in the United States of America in 9, Phase Ill in the former USSR in 99). Results of these comparison tests were already published [,,, ]. Some radiosondes used in the Asia-Pacific region including Japan did not participate in these comparisons, and the Commission for Instruments and Methods of Observation of WMO at its tenth session (CIMO-X, September, 99) recommended to conduct another phase of the comparison. Japan, responding to this recommendation, proposed to host the Phase IV comparison, and the International Organizing Committee was set up under CIMO for the preparation of the Phase IV. Participation in the comparison was called for to Members of RA-Il and RA-V and also to Finland and USA. The participating countries in Phase IV were Japan, Finland and USA and seven types of radiosondes from these countries were compared. An observer from the Republic of Korea attended part of the comparison. The WMO Radiosonde Comparison - Phase IV - was held at the Aerological Observatory of the Japan Meteorological Agency (JMA) in Tsukuba, Japan, from February through March 99. This report is the summary of the results from the Phase IV comparison. The major purpose of this comparison was to compare Japanese radiosondes with other radiosondes which had already participated in the previous comparisons. It should also be noted that so-called -thermistor radiosondes, which were developed to serve as the reference measurement of temperature, participated for the first time in the WMO radiosonde comparison. - -

7 . Radiosondes and systems used in Phase IV. Overview of participating radiosondes and systems Table is a list of radiosondes and tracking/ data processing systems which participated in Phase IV comparison. Photographs of these radiosondes are shown in Appendix A. Detailed characteristics of sensors mounted on these radiosondes are seen in Table. As shown in Table, Vaisala RS-N and AIR IS-A-HS participated in previous comparisons and were used as "link radiosondes". These radiosondes are used as a reference when results of different phases are examined. Procedures to receive data from the radiosonde, process the data to derive meteorological parameters and make a bulletin of upper-air observation in the TEMP format are fully automated in all of the systems. In this comparison, more than one kind of data sets were obtained from one Finnish model and two American models. Each data set is identified with a name of type of radiosonde such as JP as shown in Table.. Japanese systems.. RS- radiosonde (JP) This model had been used for upper-air observations in Japan since 9, and was still in operational use at a limited number of stations when the Phase IV comparison was held. This system employs a radiotheodolite for wind finding and a minicomputer or a personal computer for data processing (a system with a personal computer was used in Phase IV). The pressure sensor is a baroswitch-type aneroid capsule installed in the radiosonde body, which mechanically detects the change of the aneroid capsule with the air pressure as the change of electric resistance. The temperature sensor is a thermistor painted in white, which is mounted at the end of a cm long sensor-holding frame attached to the radiosonde body horizontally. A carbon hygristor is used for the humidity sensor, which detects the air humidity using the electric resistance of the carbon element. The carbon element is placed in an air duct at the top of the radiosonde body to shelter from both rain drops and solar radiation. Signals from the sensors are sampled every sec. for the pressure, sec. for the temperature and sec. for the humidity, and they are frequency modulated and transmitted to the ground system. The received signals are demodulated and converted to values of pressure, temperature and humidity using pre-determined calibration data. The solar radiation correction is applied for air temperature measurements in the daytime using a theoretical formula which is based on a heat balance model of the thermistor, but no infrared radiation correction is applied either in the daytime or nighttime. The solar radiation correction scheme is shown in Appendix D. As for wind measurements, angle data from the radiotheodolite is smoothed, and wind vectors are derived every minute. Particularly, elevation angle data are smoothed over the period of minutes (i.e. minutes before and after the wind derivation time) when more than minutes are passed from the launch time and the elevation angle is lower than 7 degrees. --

8 The pressure sensor is tested at the observation station to day before the launch. During the test, the sensor is put in a chamber and the pressure in the chamber is decreased from the surface pressure to about hp a, and the deviation of reading of the sensor from that of a reference barometer is checked. The sensor is judged to be good when the bias is within a specified limit, and the pressure measurements during the ascent are corrected based on this bias. When it is judged not to be good, it is not used for the observation. The pre-launch check of the temperature and humidity sensors is made using another chamber placed in the observation room within minutes before the launch. The temperature sensor is checked against the temperature reading of a reference psychrometer, while the humidity sensor is checked in a sub-chamber installed in the main chamber where the humidity is kept %. Temperature and humidity sensors whose bias is within a specified limit are identified to be good to use for the observation. Humidity measurements are corrected during the ascent using the bias found in this check... RS-9 radiosonde GP) This model was introduced into operational upper-air observations in Japan in 99 as the successor of the RS- model. It is smaller in size and lighter in weight than the RS- model. This system uses a radiotheodolite for wind finding as the RS- system and a personal computer is used for data processing. The pressure sensor is a capacitive aneroid capsule that continuously detects the change of the aneroid capsule with air pressure as the change of electric capacity. The temperature sensor is a thermistor which is coated with vacuum-evaporated aluminum to reduce infrared radiation effect. A capacitive thin polymer film element is used for the humidity sensor, which detects the ambient humidity as the electric capacity of the element. Both of the temperature- and humidity-sensors are mounted on a sensor-holding plate, which sticks out of the radiosonde body, being inclined degrees upward from the horizontal. The temperature sensor is placed at the top edge of the plate, while the humidity sensor is placed midway between the joint and the top edge of the plate. The humidity sensor wears a cap to avoid contamination from rain drops. Signals from each sensor are sampled every sec., frequency modulated and transmitted to the ground system. The received signals are demodulated and converted to the values of pressure, temperature and humidity using pre-determined calibration data. As in the RS- system, solar radiation correction are applied for air temperature measurements in the daytime using a theoretical formula which is based on a heat balance model of the thermistor, but no infrared radiation correction is applied either in the daytime or nighttime. The solar radiation correction scheme, however, differs from that of the RS- system, reflecting differences in size, shape, mounting attitude, etc. of the sensor. The solar radiation correction scheme is shown in Appendix D. The procedure for wind derivation is the same as that of the RS- system. The pressure sensor is tested at the observation station to day before the launch. The procedure of this test is same as that of the RS- system described above. The pre-launch check of the pressure, temperature and humidity sensors is made using a chamber in the observation room within minutes before the launch. The reading of sensors is compared against the air pressure at the observation room obtained from a routine surface observation and the temperature and humidity obtained with the psychrometer in the chamber. Sensors whose deviations from the reference values are within a specified limit are identified to be good to use for the observation. The pressure measurements are corrected during the ascent using the bias derived in this test. --

9 . Finnish systems.. Vaisala RS-N radiosonde (FNl, FN) This model is used for operational upper-air observations in several countries including Finland. In this radiosonde system, the Omega navaid is used for wind finding and equipment called DigiCORA is used for the data processing in the ground system. The pressure sensor is a capacitive aneroid capsule, which detects the transformation of the aneroid capsule with the change of air pressure as the electric capacity between the plates inside the capsule. The temperature sensor is a capacitive ceramic chip, which detects the change of temperature as the change of electric capacity between the electrodes attached to the chip. The ceramic chip is sealed in a glass capsule and coated with thin aluminum coating and water-repellent paint. A capacitive thin film element is used for the humidity sensor, which detects the ambient humidity as the electric capacity of the element. Both the temperature and humidity sensors are mounted on a sensor-holding plate which sticks out of the radiosonde body, being inclined upward from the horizontal. The temperature sensor is placed near the top edge of the plate, while the humidity sensor is placed midway between the joint and the top edge of the plate. The humidity sensor wears a cap to avoid contamination from rain drops. Signals from each sensor are sampled every. sec., frequency modulated and transmitted together with the omega signals received by the radiosonde. The signals received at the ground equipment are demodulated, and converted to the pressure, temperature and humidity values using pre-determined calibration data. In the daytime, solar radiation correction for air temperature measurements is made. In the nighttime, infrared radiation correction can be applied. The radiation correction scheme is shown in Appendix D. These corrections are automatically performed in the ground equipment during the ascent. As for wind measurements, the location of the radiosonde is obtained by processing Omega signals and wind vectors are calculated every seconds and recorded every minute. Pre-launch checks of the radiosonde sensors are made immediately before the launch: the pressure sensor is checked against a digital barometer which is already calibrated against the reference barometer, and temperature and humidity sensors are checked using an apparatus whose humidity is kept %. The results of these checks are put into the ground equipment, and measured pressure, temperature, and humidity values are automatically corrected in the data processing during the ascent. The following two data sets were produced from this radiosonde system in order to evaluate the effect of infrared radiation correction for temperature measurements in the nighttime: FNl: Infrared radiation correction for temperature measurements in the nighttime is made. FN: No infrared radiation correction for measurements in the nighttime is made... Vaisala RS-LH radiosonde (FN) This is a new model for operational use. The Loran-C navaid system is used for wind finding. A data processing system with a personal computer, called PC-CORA, was used in the ground system during Phase N. --

10 This model looks similar to RS-N model, except the antenna. The humidity sensor is improved with the capacitive film of a different material and the Loran-C navaid system is used for wind finding in this model, but other sensors and the data processing software have the same feature as those of RS-N. The mechanism by which the humidity sensor of this radiosonde senses the air humidity is the same as that of RS-N.. USA systems.. AIR IS-A-HS radiosonde (AR) At present, this model is not used for operational upper-air observations in the USA but is used at a limited number of stations in Asia and Antarctica. It participated in Phase IV as one of the link radiosondes in place of VIZ 9 model, which served as a link radiosonde in previous phases. In this system, a radiotheodolite is used for wind finding and a personal computer is used for data processing in the ground equipment. The pressure sensor is a capacitive aneroid capsule, which continuously detects the transformation of the aneroid capsule with the change of air pressure as the change of electric capacity. The temperature sensor is a thermistor coated with white paint, and attached horizontally to the end of a sensor-holding frame, which sticks out of the radiosonde body. This temperature sensor was manufactured by VIZ and was similar to the sensor used by the VIZ 9 radiosonde in earlier tests. A carbon hygristor is used as the humidity sensor, which senses the change of electric resistance of the carbon element with the change of air humidity. The humidity sensor is placed in an air duct located in the upper part of the radiosonde body to shelter it from both raindrops and solar radiation. Signals from each sensor are coded in a digital format by a microprocessor on board the radiosonde and transmitted every to sec. The signals received at the ground equipment are, after demodulation, transformed to pressure, temperature and humidity values. Neither solar nor infrared radiation correction is made for temperature measurements... AIR IS-A-L radiosonde (AR, AR) This is a -thermistor model developed by the National Aeronautics and Space Administration (NASA) of the USA for more accurate measurements of air temperature [7]. In this radiosonde system, the Loran-C navaid is used for wind finding and a personal computer is used for data processing in the ground equipment. Specifications of the pressure sensor and the humidity sensor are the same as those of AIR IS-A-HS radiosonde, and the way to mount them in the radiosonde is also the same. The temperature sensor, however, consists of three rod thermistors with the same shape and size. The surface of these thermistors are coated with white, aluminium and black paint, respectively, and are mounted apart from each other on the horizontal sensor-holding frame sticking out of the radiosonde body. Signals from these sensors are coded into a digital format and transmitted every to sec., as the AIR IS-A-HS model. Both solar and infrared radiation corrections are made for temperature measurements using the -thermistor method. In this method, air temperature is calibrated with readings of three thermistors painted in white, in black and coated with aluminium, whose absorption coefficients for the solar and infrared radiations are known. The outline of this method is shown in Appendix D. As for wind measurements, the position of the radiosonde is obtained from Loran-C signals received by the --

11 radiosonde, and wind vectors are derived. The following two data sets were produced from this radiosonde system in order to evaluate the effect of the -thermistor correction for air temperature. AR: -thermistor correction. The reading of the white thermistor is used as the temperature data without the AR: The -thermistor correction is made on the temperature data... VIZ Mark II MICROSONDE (VIZ, VZ, VZ) This is a new operational model in which the -thermistor mechanism developed by the NASA is installed. In this system, the Loran-C navaid is used for wind finding and a data processing system with a personal computer, called W9 is used in the ground system. The pressure sensor is a capacitive aneroid capsule, which continuously detects the transformation of the aneroid capsule with the change of air pressure change as the change of electric capacity. The temperature sensor consists of four rod thermistors. One small thermistor is coated with white paint, and the other three larger thermistors are painted in white and in black and coated with aluminium, respectively. The small thermistor is a new type for the operational use. The three larger thermistors are identical with those used in AIR IS-A-L model. These thermistors are mounted apart from each other on a horizontal sensor-holding frame sticking out of the radiosonde body. The humidity sensor is a carbon hygristor which detects the change of air humidity as the change of electric resistance of the carbon element. It is placed in the air duct located in the upper part of the radiosonde body to shelter from both raindrops and solar radiation. The sampling interval of the signals from the pressure, temperate and humidity sensors is sec.; these signals are coded into a digital format and, together with the calibration data of the sensors stored in a ROM in the radiosonde, transmitted to the ground. The received signals are demodulated and converted to values of meteorological elements based on the calibration data. In the -thermistor correction procedure for air temperature, the ~ata from larger three thermistors are used. The method of the -thermistor correction is the same as that of the AIR IS-A-L (AR) system described above. As for wind measurements, the position of the radiosonde is obtained by processing Loran-C signals received by the radiosonde, and wind vectors are derived. The following three data sets were obtained from this radiosonde system, each corresponding to different procedure for temperature data processing. VIZ: Temperature data are those of the small thermistor without any correction either for solar or infrared radiation. VZ: correction. Temperature data are those of the larger white thermistor without the -thermistor VZ: The -thermistor correction is made on the temperature data. --

12 . Description of the field test. Participants in the Phase IV The participants in the Phase IV are shown in Appendix F. Each team was responsible for preparation of their own radiosondes, and for acquisition and processing of the radiosonde data, while the host country was responsible for the management of the comparison, collection of each team's data and the logistic support of each team's observation.. Preparation of the field test The location of antennas of the teams are shown in Appendix B. The antennas of the Finnish team and the USA team were set on the roof of the building of the Aerological Observatory. The antenna of the Japanese RS-9 system was set on the roof of the building of the Aerological Observatory, which is used for routine observations. The antenna of the Japanese RS- system was set on the roof of the test laboratory apart from the building of the Aerological Observatory. Ground systems of the Japanese RS-9 system and the USA AIR IS-A-HS system were set in an observation room on the first floor of the building of the Aerological Observatory, while the ground systems of the Finnish team and of the USA AIR IS-A-L and VIZ Mark II MICROSONDE systems were set in another observation room on the third floor of the building. The ground equipment of the Japanese RS- system was set in the test laboratory. Six radiosondes were launched at a time with a TOTEX g balloon. The distance between the balloon and the radiosondes was m. The shape of the flight rig was triangle, which was made of polycarbonate or bamboo. The configuration of the flight rig and the flight train is shown in Appendix C, and its photograph with radiosondes in flight is also shown in Appendix C. Frequency bands used by the radiosondes were MHz for the Japanese team, MHz for the Finnish team, and MHz and MHz for the USA team, respectively. Necessary arrangements were made in order to avoid interference between the radiosondes during the ascent. At the time of launching the balloon, an electric start signal was supplied by the Japanese team to synchronize the timing of the data acquired by each radiosonde system. All the systems except for the USA AIR IS-A-L used this signal as a starting trigger of automatic data acquisition. In the AIR IS-A-L system, the operator started data acquisition manually with the starting signal. Synoptic observations of air pressure, temperature, humidity and wind speed and direction were made at the site at the time of launch and the data were provided to each team.. Flight schedule The maximum number of radiosondes launched simultaneously during each ascent was six. Due to this restriction, -thermistor radiosondes AIR IS-A-L and VIZ Mark II MICROSONDE were, in principle, not launched in the same rig and only one of the two models was launched together with the other five radiosondes. Three observations were made per day: one in the nighttime and two in the daytime corresponding to the high and low solar elevation. The nighttime observations were made at UTC (local time JST), while daytime observations were made at UTC ( JST) and UTC ( JST). However, on days when the routine ozone sonde observation is made at UTC, the comparison observation was made at UTC (9 JST) instead of UTC. The balloon was released minutes before the observation time. -7-

13 . Collection of the comparison data A data collection center was set up in a room on the third floor of the building of the Aerological Observatory, and each team submitted their observation data within an hour, in principle, after the observation was finished. However, the FN data of the Finnish team was submitted on the next day for the reason of data processing procedures. Since the -thermistor correction could not be made at the comparison site, results of the observations with the -thermistor correction made by the USA team (AR, VZ) were submitted after the completion of the field test. Each team submitted four kinds of data to the data collection center: pressure, temperature, relative humidity, geopotential height and wind direction and wind speed derived every two seconds, the same data derived every one minute, data at the standard pressure levels and TEMP messages. All these data were submitted in ASCII files of predetermined format on a diskette. The data derived every one minute were used for statistical calculations in the comparison of simultaneous measurements. While the data derived every two seconds were used to check the synchronization of sampling reported from different systems. In the Phase IV comparison, the International Organizing Committee (IOC) for the Phase IV provided the project leader with some personal computer software (PC-software). These programs were developed originally by Mr. S. Kurnosenko (Russian Federation) at the Phase Ill comparison. They have functions such as saving and editing radiosonde data and displaying sounding profiles on the PC. The data collection center made use of the software for editing the radiosonde data submitted by the teams. This software was provided to team leaders and used to check erroneous data. The project leader, the team leaders and other persons concerned had data evaluation meetings every night in order to review data obtained at UTC on the preceding day and at and (or ) UTC on that day. When any team found an error in their data, the team leader reported the meeting on the error. If the meeting agreed that corrections for the erroneous data are justified, the erroneous data in the comparison database were replaced with the revised data.. Schedule of the comparison test A briefing of the comparison test was made by the project leader for the participants on February 99. On February, an inspection of the frequency and transmission power of radiosondes was made by the authority of telecommunications at the Aerological Observatory. A test flight was made at : JST on that day, and it was ascertained that there was no problem in the series of procedures such as launching of the balloon, acquisition and processing of radiosonde data by each team, and collection of the data at the data collection center. The comparison observations were carried out from 7 February through March except on Sundays. During this period, the second session of the International Organizing Committee (IOC) for Phase IV was held from through February at the Aerological Observatory, Tsukuba, and at the Headquarters of JMA, Tokyo. The members of the IOC visited the comparison site on February to review the state of the comparison test and exchanged views with members of the participating teams.. Meteorological condition during the comparison period Climatological data in February /March (monthly mean value for 9-99) at the comparison --

14 site are as follows:./. hpa for surface pressure,.9/. C for air temperature, /% for air humidity,.7/.7 mm for monthly total precipitation. Because of a typical synoptic pattern in winter around Japan, the weather at the comparison site was fine in general with prevailing northwest monsoon winds from 7 February through March. During that period, lows in the developing stage with fronts passed eastward near Japan with an interval of to days, and brought precipitation at the comparison site. From through March, the winter synoptic pattern weakened, and precipitation was experienced at the comparison site due to the passage of lows. Six among the sixty flights during the comparison period experienced precipitation. The total precipitation amount during the comparison period at the site was. mm; surface air temperatures were to C higher than the climatic value in the middle ten days and in the last eight days of February, while they were normal in the first ten days of March. Westerly jet was located over Japan and strong westerlies were observed in the upper troposphere over the observation site during the comparison test..7 Achievement of flights Table shows balloon release times and the highest levels at which the radiosonde reached. To obtain twenty successful flights for each of the three time zones (one at night, two in the daytime), sixty-one flights in total were made during the comparison period. One flight (the 7th flight on February) was unsuccessful because the balloon collided with ground objects, and successful flights were sixty in total. As already described, a total of six radiosondes, i.e. five models with one thermistor and one of the two -thermistor models, were launched together at a time. The successful flight is defined as a flight from which a complete set of data was derived to calculate all elements. Table shows numbers of launches and successful flights that reached at hpa, hp a and hpa, respectively. As described in section., when flights at UTC could not be made, balloons were launched at UTC when the effect of the solar radiation was considered to be almost the same (the solar elevation angle was about degrees at UTC and degrees at UTC, respectively, at the time of balloon release). The total number of successful observations at UTC and UTC was almost the same as those at UTC and at UTC.. Compilation of the final database A database of the observations during the Phase IV comparison was produced at the time of the completion of the field observations at Tsukuba. However, it did not contain observation data from the -thermistor models. In addition, some other corrections were submitted after the comparison. These corrections are described in the following sections... The Finnish team The Finnish team computed wind vectors in FN with minute integration time until the th flight, and the integration time was changed to minutes from the th flight. After the completion of the field observations at Tsukuba, wind vectors in the first flights were re-calculated with the -minute integration time except the st and the th flight, which could not be re-processed, and the finalized dataset contains the revised data. - 9-

15 Comparisons of the -second data of FNl with other data revealed that a -second delay was contained in the nd flight of the FNl. This time lag was removed and the corrected dataset was used in the final database... The USA team It was recognized during the field observations that time signals of AR data had systematic delays because the starting signals for data acquisition in the AIR IS-A-L system was set manually. After the completion of the field observations, AR data were re-processed in the USA and these delays were adjusted. These corrected data were used in the final database. The data of AR in the nd flight data had large errors and the dataset was removed from the final database at the request of the USA team. The AR and VZ datasets were submitted after the completion of the -thermistor correction in the USA. In addition, VZ datasets, which were not subject to inclusion in the database, were added to the final database in order to evaluate the effect of the -thermistor correction. In wind computation in ARl system, smoothing of the angle data from the radiotheodolite had not been made, but it had been revealed during the field observations at Tsukuba that smoothing would give better results since it could reduce noisy components of the data. After completion of the field observations, re-computed wind data using smoothed angle data were submitted, which were employed in the final database... The Japanese team JMA commenced the operational use of the RS-9 model just several months before the Phase IV comparison, and no scheme of solar radiation correction for this model had been established yet at the time of the Phase IV comparison. Therefore the scheme for the RS- model was tentatively used for the RS-9 model during the comparison to make JP datasets. Shortly after the Phase IV comparison, JMA determined a new scheme for the solar radiation correction for the RS-9 model, which is shown in Appendix D. The Japan team submitted re-processed data using this new correction scheme, and the datasets of JP in the final database were replaced with the new ones... Completion of the final database The project leader made a decision whether datasets in the database may be replaced with re-submitted ones under the approval of the chairman of the IOC for the Phase IV. The final database was settled in December 99, and a copy of the database was distributed to the team leaders of the Phase IV and to project leaders of the previous Phases, under the agreement of the IOC. It should be noted that some re-submitted datasets lacked the TEMP message, and in these cases, the old version of the TEMP message remained in the final database and the TEMP data are not consistent with the -second data, every minute data, standard pressure level data. ARl, AR and JP contained these TEMP data. However, the inconsistency does not significantly affect the results of the analysis of TEMP messages in this report. In the course of the analysis using the final database, some problems in the quality of data were found in some datasets that were not found in the cross check during the field comparison. The - -

16 project leader decided to exclude the following datasets from the comparison: JP: FN: FN: AR: VIZ: VZ: pressure and geopotential height data in the th flight, wind data in the th flight, wind data in the th, th and th flight, wind data in the nd, th, th and 7th flight, humidity data in the st flight, wind data in the rd and th flight, temperature and geopotential height data in the th flight. - -

17 . Method of analysis As in previous phases of comparison, a multiple regression technique was used for the statistical estimation of the systematic biases between the radiosondes to be compared. The systematic bias could be obtained as the direct difference between the radiosondes flown together, which is a sample mean bias defined by Nij./ij = N :,.(Yin- Yjn)... () ij n=l. where!ij is the difference between the radiosonde models i and j, Nij is the number of paired measurements, and Yin and Yjn are the values measured by the radiosonde i and j. The subscripts i and j refer to the radiosonde model, while n refers to the occurrence of paired measurements. equation: The systematic biases should have a property of consistency in that they satisfy the following!ik =!ij -!kj... () where subscripts i, j and k refer to three different radiosonde models. The differences defined by () have this property only when there are no missing data from either of the radiosonde model to be compared. This situation cannot be expected generally: data from some radiosonde(s) could not be obtained due to such reason as the failure of the system during the flight. One way to avoid this difficulty is to apply the statistics only for the cases with no missing data, but this severely limits the estimation of the systematic biases, with many valuable data remaining unused. Furthermore, one certain radiosonde data out of seven were always missing due to the flight restriction in the Phase IV. To overcome this situation inherent in the direct differences, consistent differences instead were used as the estimate of the systematic biases. They have a property to satisfy the equation (), and the method to calculate the consistent differences is described below. expressed as The value measured by a radiosonde i at a time (or at a pressure) denoted by n can be Yin = xn + ei +Bin... () _) \ where Yin is the measured value, Xn the true value, ei the systematic error and Bin the random error. The best estimate for ei can be found by posing a condition that the weighted sum of the squares of the random errors be minimized: N M p = LLminwiB~ ==>min.... () i=l n=l where wi is the weight, and min is a parameter which takes a value of either or corresponding to the case in which data are obtained or not obtained. The above condition leads to a system of simultaneous linear equations for the consistent difference ei- ej: - -

18 where M is the number of occurrence of measurements, and N the number of radiosonde models. Details of the above method are described elsewhere []. In practice, PC-based software was developed by Mr. Kumosenko (the Russian Federation) utilizing the above algorithm, and it was used in the analysis of the Phase IV data. This software was used in the Phase Ill comparison and later further improved in cooperation with the UK Meteorological Office []. For the comparison of simultaneous measurements, every minute data obtained in each flight were grouped into categories according to the pressure value, which are shown in Table. The average of the pressure values obtained by all radiosondes at each minute was used for the grouping of the simultaneous data. Compared with the pressure categories used in the Phase Ill, the lowest and the highest pressure ranges were newly added. The data from different flights in the same pressure range were gathered to make a dataset, and consistent differences and standard deviations were calculated for the pressure ranges. - -

19 . Link radiosonde performance relative to earlier phases It was agreed in the second session of the IOC (- February 99) that the AIR IS-A-HS and the Vaisala RS-N be used as link radiosondes for the Phase IV. In the previous phases from I through Ill, VIZ 9 and Vaisala RS-N served as link radiosondes. Ideally, the same models should be used as the link radiosonde through all phases of the comparison. However, the VIZ 9 model was not used in the Phase IV since the USA had ceased the operational use of this model by the time of the Phase IV comparison. Additional comparisons were made in UK and in the USA between the VIZ 9 model and the AIR IS-A-HS model, and AIR IS-A-HS, which participated in the Phase Ill, was suggested as an alternative for the VIZ 9 model. This was because the AIR radiosonde used the same temperature sensor. However, the measurements from the AIR radiosonde during the day should not be considered equivalent to those of VIZ 9. Differences in the mounting of the temperature sensors between the radiosonde type may produce different heating effects in daylight conditions. Vaisala RS-N was also used as the link radiosonde. This V aisala model became to use Surface Mount Technology (SMT), which is a modem technology of electronics aimed at improving the quality of signals from the radiosonde and lowering the cost. The IOC, in the second session, recognized that the SMT has no significant effect on the quality of measurement. Performance of the link radiosondes in the Phase IV with respect to temperature, pressure, etc. will be discussed in relevant sections of this report. --

20 . Comparison of simultaneous measurements The radiosonde observations were made at UTC in the nighttime, and UTC, UTC, and UTC in the daytime, as described in Chapter. The solar elevation angle at the time of the day flight was -9 degrees for UTC, - degrees for UTC, and 9- degrees for UTC. In order to evaluate the effect of solar and infrared radiation, datasets were grouped into three time zones: UTC, UTC and and UTC before the analysis of temperature, pressure and geopotential. Datasets at UTC and UTC were processed together because the number of observations was too small to make statistical analysis and because there were no large difference in solar elevation angles in the two observation times. In the analysis of temperature, pressure and geopotential height, the reference data were the average of the data derived every one minute with the link radiosondes (AR and FN) and the consistent difference and the standard deviation were calculated against the reference. As for the wind data, the reference was the data with FN, which uses the Loran-C navaid, or JP, which uses the radiotheodolite for the wind finding. In Figures.-.,.-.,.,. and.-. presented hereafter, the upper figure of the paired numbers in the table right of the figure denotes the bias or the standard deviation for temperature, pressure, geopotential height, wind direction and wind speed, while the lower ones denotes the number of data used in the statistical calculations. In Figures.-. and.-., numbers in a table below the figure are: a bias or a standard deviation of relative humidity (out of the parentheses) and the number of data used for the analysis (in the parentheses).. Temperature It is known that measurements of air temperature are affected by the rate of ascent of the radiosonde, the wake from the balloon, sensor characteristics and the solar and infrared radiation. The wake from the rig may also affect the measurement in the comparison flights. It is reported that in the Phase Ill, the rate of ascent of the balloon in the stratosphere was lower than that of a balloon adopted in operational observations: i.e. -. m/ s. In the Phase IV, the buoyancy of the balloon was set so that the rate of ascent was not so different from that in routine observations. Fig. shows rates of ascent, which was calculated from the mean geopotential height of the two link radiosondes FN and AR derived every one minute. It can be seen that the rate of ascent is -7 m/ s in the troposphere and -7 m/sin the stratosphere. The temperature of the balloon is in general not equal to the ambient air temperature due to the heating by the solar radiation and by the infrared radiative cooling. It has been suggested that the air temperature measured by the radiosondes is affected by the wake from the balloon, although comparisons between instruments hung at m and m below the balloons in Phase I showed no evidence of significant balloon influence. In order to minimize possible effects, the rig from which the radiosondes are hung was placed m below the balloon. Furthermore, the radiosondes flown together were hung from the apexes and sides of the triangle-shaped rig... Link radiosondes In order to verify the consistency of characteristics of link radiosondes between Phase III and - -

21 Phase IV, the systematic difference in the measurement of temperature between Vaisala RS-N and AIR-IS-A-(HS) was compared between Phase Ill and Phase IV as shown in Table. The number of flights (and therefore the number of data) used to obtain systematic differences between the link radiosondes did not differ much between Phase Ill and Phase IV for each observation time: it was ten-and-several times, depending on the pressure level. This pertains also to Tables 7 and. During the Phase IV, temperatures observed with FN were higher than those with ARl throughout the whole layer in the nighttime, but they agreed within. C up to the hpa level. The difference grew above the hpa level with the altitude and became. C at the hpa level. The difference was smaller by. oc (in the troposphere) and by. C (in the stratosphere), compared with that in the Phase IlL In the midday, temperatures observed with FNl were lower than those with ARl, and the difference was larger than the difference in the nighttime. The difference grew with the altitude and reached. C and. oc at the hpa and hpa level, respectively. Compared with the comparison in the Phase III, the difference was larger in the troposphere and smaller in the stratosphere. The difference in the morning/ afternoon was similar to that in the midday, and that in the evening during the Phase Ill... Results Fig.. shows consistent differences and standard deviations of air temperature profile against the mean profile of AR and FN in the nighttime observations ( UTC). Up to the 7 hpa level, the differences between the biases were within. C. Above the hp a level, FN has a positive bias and readings are consistently higher than the reference; JP, AR, VZ and FN show very small biases; AR, AR, JP, VIZ and VZ show negative biases. The difference between biases grows larger with the altitude and it reaches to. C at the hpa level. This result reflects the difference in characteristics of the temperature sensors with respect to the infrared radiation and in the infrared radiation corrections applied to them. The infrared radiation correction was made to FN based on an empirical formula and the -thermistor correction was made to AR and VZ. No corrections were made to the other systems. Temperature sensors in FN (FN) and JP were coated with aluminum, while temperature sensors of the other systems were coated with white paint. It is now accepted that the infrared radiation correction for FN was not adequate, given that the temperature values obtained with the -thermistor radiosondes are closest to the true value. Profiles of JP and FN, both coated with aluminum, were similar each other. The bias between the two is nearly constant with slight increase toward the upper layers. Besides the difference in the shape of the sensor, the sensor of FN was coated with water-repellent material. Characteristics of the water-repellent material with respect to the infrared radiation may be different from those of the aluminum coating, and it is suggested that this difference in the characteristics caused the observed difference. The temperature profile of JP is closest to the reference profile above the hpa level. Fig. shows the differences of observed temperature in the midday ( UTC). Solar radiation corrections based on theoretical/ empirical formulas are applied to FN, JP and JP; -thermistor corrections are applied to AR and VZ. No radiation corrections are applied to the other systems. - -

22 Differences in the bias among FN, JP and JP were within. C up to the 7 hpa level, suggesting that the solar radiation corrections based on the theoretical/ empirical formula are effective. Above the hpa level, however, the differences become large, and the difference between FN and JP at the hpa level reaches.9 C. The temperature observed with JP was lower than that with FN and JP, and was. C lower than the reference at the hpa level. AR and AR showed almost constant bias between them. These biases were not observed in the nighttime measurements. Because (i) the profiles of standard deviation of the two systems are almost same; (ii) the bias was found even in the lowest tropospheric layers where the effect of the solar radiation is small and (ill) the differences between AR and other radiosondes are small, it is suggested that the AR temperature in the daytime contains some bias, which is not caused by the solar radiation. Fig. shows the consistent differences in the morning/ afternoon ( UTC and UTC) observations. The profiles are similar to those for the midday observations. AR has some systematic differences as in the case of the midday observations... Effects of contamination from water drops (case study) Contamination from water drops on the temperature sensor may bring large errors in the measurement of air temperature, when they attach to or evaporate from the sensor. In the Phase IV comparison, a typical case that indicates these effects was observed as described below. The radiosondes launched at UTC on 7 February 99 passed through the top of a low-level cloud at minutes seconds after the launch. The humidity dropped rapidly and readings of temperature with the radiosondes showed large differences (Fig..,.). Air temperatures observed with FN were higher than those with other radiosondes during a few minutes after the passage and the difference reached to about C at 7 minutes second The FN sensor was coated with water-repellent material. In addition, the thermistor rods of FN were mounted with an inclination of about degrees upward from the horizontal for easy falling of water drops. This case suggests that these techniques reduced the effect of water drops and the radiosondes except FN measured the air temperature systematically low.. Pressure All pressure data in the Phase IV were obtained with the aneroid capsule installed in the radiosonde. JP uses a baroswitch type, while the others use a capacitive type. The mean profile of AR and FN was used as the reference profile... Link radiosondes In order to verify the consistency of characteristics of link radiosondes between Phase III and Phase IV, the systematic difference in the measurement of pressure between Vaisala RS-N and AIR-IS-A-(HS) was compared between Phase Ill and Phase IV as shown in Table 7. During the Phase IV, the difference in pressure did not depend on the observation time. The maximum difference was observed between the hpa and hpa levels where the pressure with FN was about hpa lower than that with ARl. The profile of the difference was similar to that in the Phase Ill, except above the hpa level. The maximum difference was about. hpa smaller than that in the Phase IlL - 7-

23 .. Results Figs.. and. show consistent differences and standard deviations of measured pressure against the reference profile for each observation time. As profiles in the morning/ afternoon were very similar to those in the midday, only the latter profiles are shown here. Characteristics of the biases do not vary so much between the observations in the nighttime and in the daytime, and the biases of most radiosondes were within. hpa up to the hpa level. Though the pressure sensor of AR is the same model as that of AR, AR has some bias relative to ARl. This bias is about. hpa in the daytime observations, and it reaches about hpa below the hpa level in the nighttime. The bias is found even in the lowest layer and is almost constant throughout the whole layer. VIZ showed the largest bias among the radiosondes. But its standard deviation is almost equal to the others, suggesting that some bias is included in the calibration of VIZ. The relative bias of VIZ from the reference was more than % in the stratosphere, and these biases caused some effects on the calculation of geopotential height, as will be seen in the next section. Both biases and standard deviations of JP were large below the hp a level for all observation times. As the pressure sensor of JP was the baroswitch type, pressure values of JP were obtained at discrete points, and the pressure value between these points were calculated using the relationship between pressure and altitude with the assumption that the rate of ascent is constant between the two points. This may cause the large standard deviation when actual rate of ascent varies randomly. And as the rate of ascent below hpa generally increases with altitude (see Fig. ), the above assumption may generate negative biases.. Geopotential height All data of geopotential height in the Phase N were obtained from the pressure, temperature and humidity data using the hydrostatic equilibrium equation... Link radiosondes In order to verify the consistency of characteristics of link radiosondes between Phase III and Phase N, the systematic difference in the measurement of geopotential height between Vaisala RS-N and AIR-IS-A-(HS) was compared between Phase Ill and Phase IV as shown in Table. During the Phase N, the geopotential height observed with FN was larger than that with AR throughout the whole layer in the nighttime. The difference was within m up to the hpa level, and remained within m between and hpa levels. It rapidly increased above the level of hpa and exceeded m at the hpa level. Compared with the difference between the comparison during the Phase Ill, the difference was in general smaller except at the hp a level. For the layers above the hpa level in the midday observations, the geopotential height with FN was lower than that with AR during the Phase IV, but the opposite tendency was observed in the Phase Ill. The profile of the difference with pressure was not simple, but the difference was within m up to the hpa level, and remained within m throughout the whole layer. The difference in the morning/ afternoon was similar to that in the midday, and similar difference was observed in the morning observations rather than in the evening ones during the Phase Ill. - -

24 .. Results Fig.. and. show consistent differences and standard deviations of geopotential height. As profiles in the morning/ afternoon were very similar to those in the midday, only the latter profiles are shown here. In the nighttime, large negative biases of VIZ (< - m) were observed above the hpa level and AR showed large negative biases above the hpa level. The bias of these radiosondes at the hpa level was - m (VIZ) and - m (AR). On the other hand, positive biases of FN, JP and AR increased above the hpa level, but the differences among them were within m. Among the radiosondes, biases of FN, FN and JP agreed very well up to 7 hpa, with maximum difference of about m at the hpa level (the only difference in the procedure of FN and FN was the infrared radiation correction). The pressure values of VIZ and AR around the hpa level were larger than those of other radiosondes, which may be the cause of the negative biases of geopotential height seen around the hpa level. In the midday observations, observations with JP and JP agreed well. On the other hand, the geopotential height with FN in the daytime, which was close to the JP observation in the nighttime, was lower than that of JP above the hpa level and the difference reached to about m at the hpa level. The difference in their temperature data contributed to this difference.. Relative humidity It is known that measurements of relative humidity depend on pressure, temperature, solar radiation and contamination from water drops on the sensor. Moreover, the relative humidity can change rapidly when the radiosonde passes through the cloud. Therefore the method used in the preceding sections for the analysis of the temperature, pressure, and geopotential height is not adequate for the purpose of investigating the performance of humidity sensors. So, before statistical calculations for relative humidity data were performed, the humidity data were categorized according to the humidity and the temperature without considering the time after the launch. Differences from the reference, which is the average of FN and AR, were obtained for each of the % humidity ranges from to %, and also for each of the C temperature ranges from - to + C. In the Figs.-. and.-., values on the abscissa indicate the central values for these humidity I temperature ranges... Results Fig. and. show consistent differences and standard deviations of measured relative humidity plotted against the humidity ranges. The capacitive thin film sensor was used in JP, FN and FN, while the carbon hygristor was used in the other systems. FN, FN, AR and AR showed stable performance in the humidity range above %. FNl and ARl agreed well with a difference smaller than % in this humidity range. In the humidity range below %, ARl was higher than FNl. The difference becomes maximum in the -% range and is larger than %. The difference in the low humidity range is caused by the fact that ARl seldom showed humidity values smaller than %. When the humidity of FN took a value of - %, the corresponding value of AR was often ten-and-several percent. This may be due to the characteristics of the carbon hygristor as well as the algorithm used to deduce the relative humidity, because the algorithm was initially designed to prevent low relative humidity values being reported. VIZ read the humidity higher than the reference in the high humidity range. This results from the fact that VIZ frequently reported a humidity value of %when it entered into a moist - 9-

25 layer, and even after it goes out into a dry layer, the sensor did not response for a while. An example of these cases is shown in Fig. 7. JP has negative biases compared with AR and AR, all of them using the carbon hygristor in all humidity ranges. This bias became larger in higher humidity ranges and reached to % in the humidity range above %. JP, FN and FN, all of them using the capacitive sensor showed very similar characteristics in their biases in the humidity range below % and the difference between them was within %. But JP showed a significant negative bias in the humidity range above % while the other sensors showed biases less than %. An investigation that was conducted after the completion of the field observations at Tsukuba revealed that the humidity sensor used in JP had a tendency to show humidity values lower than the real value as time passes after the calibration made at manufacturing. Fig. and. show consistent differences and standard deviations of the relative humidity plotted against the temperature ranges. It was observed that both the bias and standard deviation of humidity became large below the freezing point, indicating the importance of the calibration and the information on sensor characteristics in the temperature ranges below the freezing point... Case study Statistical features described above were well observed during the flight at UTC on March 99. Fig. 9 shows the humidity data taken every one minute during the flight. Two to four minutes after the launch, JP and JP showed humidity values lower than the surface humidity, while the others showed humidity near %. This is a typical example that Japanese radiosondes do not report humidity near %. Twenty minutes after the launch and later, all radiosondes except FN reported constant humidity. FNl, JP and VIZ reported humidity of several percent, while AR, AR and JP reported humidity larger than %. Among the radiosondes with the carbon hygristor, only VIZ reported humidities below %.. Wind JP, JP and AR use the radiotheodolite for the determination of location of the radiosonde, while FN, AR and VIZ use Loran C navaid system and FN uses Omega navaid system. Radiosondes using a navaid system were sometimes affected by magnetic storms occurred during the comparison period. They were also affected by a wind profiler radar operated near the comparison site. The wind data affected by these events were removed from statistical calculations, as described in section.. As the location of the antenna of JP was not so high from the ground, wind data from JP above around the hpa level were frequently lost when the elevation angle of the radiosonde became low and ground objects shaded it... Consistent differences and standard deviations In the calculation of the consistent difference and the standard deviation, the reference was taken to be either FN or JP, in order to have an insight into the characteristics of the wind finding methods (FN uses the Loran C navaid system and JP uses the radiotheodolite). Fig.. shows consistent differences and standard deviations of wind speeds. Differences of wind speeds from the reference did not exceed. m/ s, except AR at the hp a level and JP --

26 between and hpa. In a few flights, AR reported wind speeds much weaker than the other systems during several minutes after the launch, the reason of which is unknown. Wind speeds observed with JP were generally weaker than other observations and the negative bias from the reference exceeded - m/ s at the hp a level. An investigation that was conducted after the completion of the field observations revealed that the elevation angle measured with the radiotheodolite of JP had a bias of about. degree, which can explain the negative bias. Japan recalculated winds after the correction of this bias in the elevation angle, and found that the bias from the JP became less than m/ s (see Appendix E). It was also observed that the peak of the maximum wind speed with JP is not so sharp as those with other systems. Elevation angles with JP (and also in JP) are smoothed when the elevation angle is lower than 7 degrees. When the elevation angle becomes low, angle data measured with a radiotheodolite are affected by stray signals by the reflection from the ground that generate errors in the measured angle data. The effect of errors in the elevation angle on the calculated wind speeds are large when the elevation angle is low. The smoothing procedure aims at obtaining stable wind speeds at low elevation angles. However, the comparison results suggest the smoothing is too intense to obtain detailed wind profiles. other systems. The standard deviation of wind speeds with AR was about twice as large as those with the Fig.. shows consistent differences and standard deviations of wind directions. The difference of the wind direction between the systems was within about degree. Relatively large difference of the wind direction was seen in the stratosphere. But winds in the stratosphere are weak and the vector wind differences are not so large... Scatter diagrams and histograms In order to see the characteristic features of differences of the wind data in more detail, scatter diagrams and histograms of the vector wind differences were prepared, taking FN as the reference. The results are shown in Fig..-.. In these calculations, a pressure level of hpa (see Table ) was selected, which represents the level of the westerly jet. Note that the wind from east and north is taken to be positive in contrast to the meteorological convention for naming component winds. An ellipse in which % of data are found is drawn in the scatter diagram. Among the systems using the Loran C navaid, the dispersion of VIZ was the smallest. AR had a large dispersion. JP had a large bias exceeding m/ s, which was due to a bias contained in the data of elevation angle from the radiotheodolite as described in... In the wind finding system using the theodolite, random errors in measured angle data cause large errors in the location of the radiosonde, especially when the elevation angle is low, resulting in errors in the calculated wind vector. This error was large in the radial component (i.e. the component in the direction in which the radiosonde is leaving/approaching the observation site) rather than in the tangential component. The radial direction is close to the east-west direction in the upper troposphere and so a large dispersion in the east-west direction was observed with JP and AR data. The dispersion of JP was relatively small, though it employs a radiotheodolite. This can be explained by the fact that the wind data corresponding to very low elevation angles were not contained in JP due to the location of the antenna. - -

27 7. Results from -thermistor radiosondes In the Phase IV, AIR and VIZ radiosondes use the -thermistor mechanism. The data with the -thermistor correction are denoted as AR and VZ. The corresponding data without the -thermistor correction are denoted as AR and VZ, respectively. Specifications of the -thermistor sensor and the data processing method of these two radiosondes are the same, as already described in Chapter. These -thermistor radiosondes were usually flown alternately except three flights in which both radiosondes were flown together, and simultaneous data were obtained at UTC on 7 February and at UTC on March. 7. Consistent differences Fig..-. show that temperature readings of AR and VZ without the correction agreed within. C at any observation time. Temperature differences between AR and VZ with the -thermistor correction were almost equal to those without the correction, except in the layer above the hpa level in the morning/ afternoon ( UTC and UTC) observations. In these layers in the morning/ afternoon observations, the temperature with VZ gradually became higher compared to AR and the difference reached.7 C at the hpa level, but similar features were not seen in the midday observations. 7. Amount of temperature correction Fig..-. show the amount of corrections which was obtained as the average of differences between temperatures with and without the -thermistor correction. In the nighttime, the amount of correction was within. C up to the 7 hpa level. The difference grew gradually above the hpa level and reached +. C (AR) and +. C (VZ), respectively, at the hpa level. In the midday, the amount was the largest between 7 and hpa level with the maximum value of -. C. Both profiles of correction up to the hpa level agreed very well with the profiles obtained by Schrnidlin et al. [7]. It would be noteworthy that the correction was positive at the 7 hpa level, since it means that the cooling of the sensor caused by the infrared radiation exceeded the heating by the solar radiation. This result was not reported in previous studies [7,, 9, ], and more detailed investigations are needed. The amount of positive corrections at the 7 hpa level in the morning/ afternoon flight was larger than that in the midday, because of reduced effect of solar radiation in the morning/ afternoon. 7. Results from simultaneous flights (case study) Fig.. shows differences between temperatures without the -thermistor correction and the reference temperatures (average of FNl and ARl) taken every one minute. The difference between temperatures from the -thermistor radiosondes was small. The temperature difference rarely exceeded. C both in flights at UTC on 7 February and at UTC on March. Differences of the temperature with the -thermistor correction are shown in Fig... In the flight at UTC on March, large differences between temperatures with the two -thermistor radiosondes were recorded from 7 to minutes after the launch although differences of temperature without the correction were small. - -

28 . Comparison at standard pressure levels The results presented in the preceding chapters, i.e. comparison of simultaneous measurements presented in Chapter and results from -thermistor radiosondes presented in Chapter 7, will provide radiosonde manufacturers and those involved in upper-air observations with useful information on the improvement of radiosonde instruments and data processing procedures. On the other hand, the comparison at standard pressure levels to be presented in this chapter will be useful to users of radiosonde data, especially those involved in numerical weather prediction. In the following, consistent differences and standard deviations of temperature and geopotential are presented, respectively, taking the average of the two link radiosonde data as a reference. The consistent difference can be used as a bias correction when the radiosonde data are used, while the standard deviation can be regarded as an estimate of measurement precision. It should be pointed out that the number of samples used in statistical calculations were extremely small for some radiosondes at certain observation times. For example, AR and AR data for UTC were available in only two flights, resulting in poor reliability of their differences and standard deviations calculated.. Temperature Fig.. and. show the results for the temperature. As profiles in the morning/ afternoon were very similar to those in the midday, only the latter profiles are shown here. The difference between the link radiosondes is within. C up to the 7 hpa level in the nighttime. The difference became gradually large above hpa, and reached about. C at the hpa level. The standard deviations were smaller than those reported in the preceding phase, both in the daytime and in the nighttime observations. The standard deviations of temperature obtained from radiosondes were almost within. "C up to the hp a level, and within C up to the hpa level. It can be said that the temperature data up to the hpa level satisfy the accuracy requirements of WMO [].. Geopotential height Fig. and. show the results for the geopotential height. As profiles in the morning/ afternoon were very similar to those in the midday, only the latter profiles are shown here. The standard deviations of geopotential height were less than m up to the hpa level, and less than m up to the hpa level. The standard deviations relative to the values of geopotential height were less than.% at all pressure levels. It can be said that the geopotential data also satisfy the accuracy requirements of WMO at all pressure levels. --

29 9. Analysis of TEMP messages TEMP messages via the Global Telecommunication System (GTS) serve for quasi-real time use of the upper-air data obtained by radiosonde observations in national meteorological services. In the Phase IV, TEMP messages were submitted from eight systems, i.e. AR, AR, FN, FN, FN, JP, JP, and VIZ. The difference in TEMP messages will be caused not only by the difference in the measured meteorological values but also by the difference in the algorithm used for the selection of significant levels and tropopause levels. As mentioned in section., there were some cases in which every minute data were revised and re-submitted, but in many of such cases TEMP data were not revised. Therefore it is difficult to evaluate how well the TEMP messages reproduce the original observations for those cases. On the other hand, apparent errors to be due to mistakes in message coding processes were never found, and the number of significant levels selected to reproduce the original observations did not differ so much among the systems. These are attributed to the fully automated systems used in the Phase IV. 9. Tropopause level The number of tropopause and the tropopause heights reported from the participating systems differed greatly among them. Fig.. shows a time series of the tropopause height (expressed as the pressure level). The maximum number of tropopause reported in each flight was one in AR and AR, two in FN, FN, and FN, four in VIZ and five in JP and JP. There exist no marked differences among the temperature profiles reproduced from the TEMP messages of these systems, and therefore it seems that the number of tropopause to be reported may be restricted in AR, AR, FN, FN and FN systems. Selection of the tropopause are made on the basis of the temperature lapse rate of. C/km, so that the tropopause in synoptic scale is likely to be missed when only the first tropopause is reported. In many cases the height of the first tropopause was reported to be below the hpa level in the Phase IV comparison, while the average tropopause in synoptic scale exists near the hpa level according to the monthly climatological data at Tsukuba. In fact, individual upper-air data obtained in the Phase IV suggest that the temperature begins to increase near the hpa level. The tropopause in synoptic scale should be reported in TEMP messages. In some cases a level just hpa or below was reported as a tropopause level in AR, AR, FN, FN and FN data. Fig.. shows an example of those cases, in which the temperature profiles at UTC on February 99 reproduced from the TEMP messages are plotted. In this case AR, AR, FN and FN reported the hpa level as the first tropopause; however to take this level as the tropopause is not in accordance with the definition of the tropopause []. In this case a level near 9 hpa should be reported as the first tropopause as in JP and JP, since the data are obtained beyond the hpa level upward. Even if the observations were terminated at some level below the hpa level, the first tropopause should be near the hpa level, not just the hpa level. It seems that the algorithms used to select tropopause in Finnish and AIR systems need some improvement. --

30 . Conclusions WMO Radiosonde Comparison -Phase IV- was held at the Aerological Observatory, Tsukuba, Japan, from February through March 99. Radiosondes from Japan, Finland and the USA were compared, with the link radiosondes being the same, or compatible with, those of the previous phases. The -thermistor radiosondes, which are considered to provide reference measurements for air temperature, participated in the WMO radiosonde comparison for the first time. The timing of sampling of the data was carefully synchronized among the systems by using the data obtained every two seconds by each radiosonde. A total of successful flights were made during the comparison period, including flights in the nighttime, flights in the midday with solar elevation angle larger than 7 degrees and flights in the morning/ afternoon flights with solar elevation angle smaller than 7 degrees. The number of flights in which all the radiosondes flown together reported data up to the hpa level were, and times for the nighttime, the midday and the morning/afternoon, respectively.. Temperature In the nighttime, temperatures measured simultaneously by the all participating radiosondes agreed within. C up to the 7 hpa level. Above the 7 hpa level, the differences among them increase to a maximum value of. C, but temperatures obtained from aluminium-coated thermistor without infrared radiation correction (JP and FN) agree well with those obtained from the -thermistor radiosondes within about. C. In the daytime, temperatures obtained after the solar radiation correction (FN, JP and JP) agreed within. C up to the 7 hpa level, and their differences from those obtained from -thermistor radiosondes were within. C. Above the 7 hpa level, the differences among the temperatures obtained after the solar radiation correction increased and exceeded of. C, while the difference between the temperatures obtained from -thermistor radiosondes reached.7 o C. From a case study in which the temperature measurements were considered to be affected by contamination from water drops on the sensor, it is suggested that the water-repellent material on the temperature sensor or device designed to mount the sensor can reduce the effect of water drops.. Pressure Measurements of the air pressure were only slightly affected by the time the measurements were made. VIZ tends to exhibit large pressure values as compared with the other radiosondes.. Geopotential height In the nighttime, differences among the radiosondes were within m up to the hpa level, except AR and VIZ. The relatively large difference of AR and VIZ in the upper layers could be due to the difference in their pressure measurements. In the midday, differences among the radiosondes were within m up to the hpa level, except FN and VIZ. The relatively large differences of FN and VIZ could be due to the differences in temperature (FN) and in pressure (VIZ) measurements. - -

31 . Relative humidity There existed large humidity differences in the low humidity range, according to the type of the sensor (capacitive film or carbon hygristor); it is necessary to standardize the calibration procedure in the low humidity range, especially below the freezing point.. Wind Westerly jets were located over the comparison site in the Phase IV period, which would be unfavorable to the wind measurements using a radiotheodolite, since the elevation of radiosondes seen from the site becomes very low. In spite of these circumstances, measured winds agreed fairly well. As demonstrated in JP system, more careful attention should be given to the set up and periodical checking of the radiotheodolites.. -thermistor radiosondes Though the two types of -thermistor radiosondes use the same model of sensor and temperature correction procedures are the same, a difference of. C at maximum were occurred. The difference between the temperatures after the -thermistor correction was smaller than that before the correction in the nighttime, but the reverse feature was seen in the daytime. More detailed study on the performance of the -thermistor radiosonde seems to be needed by conducting simultaneous flights with more than one -thermistor radiosondes..7 Comparison at standard pressure levels Judging from the standard deviations of the data, all radiosondes that participated in the Phase IV comparison satisfied the accuracy requirements of WMO up to the hpa (for temperature) and hpa level (geopotential height), respectively.. TEMP messages All the participating systems in the Phase IV automatically produced TEMP messages, and apparent errors due to mistakes in coding of the messages were never found. However, in some systems the tropopause levels were not chosen as defined in WMO Guide, and some improvement seems to be necessary. --

32 Acknowledgments The authors would like to express their gratitude to the International Organizing Committee (IOC) for the Phase IV comparison chaired by Dr. J. Nash, for their assistance extended to us. The guidelines provided by the Committee during all stages of the comparison, i.e. planning, implementation, data analysis and preparation of the report, were most important to the success of the comparison. We also wish to thank the WMO Secretariat for their support and encouragement throughout the comparison. The field observations at Tsukuba required working hours from the morning till late at night over the period of about four weeks. All of the team members who participated in the Phase IV performed these hard works with diligence and patience to acquire a large amount of valuable data. We express sincere thanks to them. Mr. S. Kumosenko of Russian Federation visited Japan Meteorological Agency (JMA) as a software consultant immediately after the completion of the field observations at Tsukuba. He made significant improvements in the data analysis software for the Phase IV. We are grateful to him, and also to the Central Aerological Observatory, Russian Federation, that kindly dispatched him. The preparation of the comparison as the host country was made in close collaboration between the Aerological Division, Headquarters of JMA, and the Aerological Observatory. Particularly, the staff of the Second Observation Section of the Aerological Observatory, headed by Mr. N. Hayashi, made substantial efforts for the smooth operation of the comparison. Also, the staff of the Office for International Affairs, Planning Division of JMA, made efforts for the success of the comparison, e.g. by acting as the local secretariat of the sessions of the IOC held in Japan. Miss R. Nakamura of the Aerological Division helped us in preparing most of the figures used in this report. Without her help and encouragement, this report could not have been accomplished. -7-

33 References. Hooper, A.H., 9: WMO International Radiosonde Comparison Phase I (Beaufort Park, U.K. 9). WMO Instruments and Observing Methods Report No., pp.. Nash, J. and F.J. Schmidlin, 97: WMO International Radiosonde Comparison (U.K.9, U.S.A. 9) Final Report. WMO Instruments and Observing Methods Report No., pp.. Schmidlin, F.J., 9: WMO International Radiosonde Comparison Phase II, 9. WMO Instruments and Observing Methods Report No.9, pp.. Ivanov A., A. Kats, S. Kurnosenko, J. Nash and N. Zaitseva, 99: WMO International Radiosonde Comparison (Phase Ill, Dzhambul, USSR, 99) Final Report. WMO Instruments and Observing Methods Report No., 7pp.. Hooper, A.H. and J.F. Panting, 9: Analysis schemes for treating data from radiosonde intercomparisons. International Organizing Committee for Radiosonde Intercomparison 9. Report of first session, Annex I.. Ivanov, A. and S. Kurnosenko, 99: Instruments,observations,and processing software for the phase III radiosonde intercomparison. Russian Meteorology and Hydrology.,, Schmidlin, F.J., J.K. Luers and P.D. Huffman, 9: Preliminary estimates of radiosonde thermistor errors. NASA Technical Paper 7.. Antikainen, V. and H. Turtiainen, 99: Solar and infrared temperature correction studies with a special Vaisala RS-radiosonde. Papers presented at the TEC-9, Vienna, Austria, - May 99, WMO Instruments and Observing Methods Report No.9, Schmidlin, F.J., 99: Development and application of a reference temperature radiosonde. Papers presented at the TEC-9, Vienna, Austria, - May 99, WMO Instruments and Observing Methods Report No.9, 9-.. Luers J.K., F.J. Schmidlin, 99: Evaluation of temperature measurements from -thermistor reference radiosonde. Papers presented at the TEC-9, Vienna, Austria, - May 99, WMO Instruments and Observing Methods Report No.9, -.. WMO, 9: Guide to Meteorological Instruments and Methods of Observation (Fifth edition), WMO-No., Annex.A.. WMO, 9: Guide to Climatological Practices (First edition), WMO-No., Annex.A. - -

34 Tables Table List of radiosondes and tracking / data processing systems Table Sensors mounted on the radiosondes Table The observational programme fulfilment Table Numbers of launches and successful flights Table Pressure categories used in the comparison of simultaneous measurements Table Simultaneous temperature comparisons between the link radiosondes of the Phase IV and the same radiosonde models participating in the Phase Ill Table 7 Simultaneous pressure comparisons between the link radiosondes of the Phase IV and the same radiosonde models participating in the Phase Ill Table Simultaneous geopotential height comparisons between the link radiosondes of the Phase IV and the same radiosonde models participating in the Phase Ill -9-

35 Table List of radiosondes and tracking I data processing systems Country Name of Name of Type of Transmission Wind finding Data Radiation Weight Participation manufacturer tracking/ radiosonde frequency equipment Processing correction (g) in previous processing (MHz) phases system I II m Japan Meisei JMA-DB- RS- 7 Radio- Fully Yes 7 system theodolite automated N N N (JPl) Japan Meisei JMA-9 RS-9 Radio- Fully Yes system theodolite automated N N N CJP) vl I Finland Vaisala DigiCora RS-N. Omega Fully FN :Yes automated FN:Yes y y y CFNl, FN) Finland Vaisala PC Cora RS-LH. Loran C Fully Yes automated (FN) N N N USA AIR IS-A-HS 7 Radio- Fully No theodolite automated N N y CARD. USA AIR IS-A-L. Loran C Fully AR:No automated AR:Yes N N N CAR,AR) USA VIZ W-9 Mark II. Loran C Fully VIZ:No MICROSONDE automated VZ:No N N N (VIZ, VZ, VZ) VZ:Yes

36 Table Sensors mounted on the radiosondes Temperature sensor Humidity sensor Pressure sensor Type of Type Size Time constana Range Type Time constant* Range Type Resolution Range radiosonde (mm) (s) ("C) (sec) (%) (hpa) (hpa) Surface lohpa Surface lohpa Meisei Rod. X r/j.. ~ -9~+ Resistive l - ~ Baroswitch o. l ~ RS- thermistor () () carbon () aneroid capsule Meisei Rod. X r/j.. ~ --+ Capacitive - ~ Capacitive o. l - RS-9 thermistor () () thin film () aneroid capsule -C.,.) capsule ' Vaisala Capacitive. X r/j.. ~ -9-+ Capacitive l - ~ Capacitive o. - RS-N ceramic () () thin film () aneroid chip Vaisala Capacitive. X r/j.. ~ -9-+ Capacitive - o- Capacitive o. - RS-LH ceramic () () thin film () aneroid chip capsule AIR Rod. X r/j l.. ~ -9-+ Resistive ~ - Capacitive o. - IS-A-HS thermistor () () carbon () aneroid capsule AIR Rod. X r/j.. ~ -9-+ Resistive _..., - Capacitive o. - IS-A-L thermistor** () () carbon () aneroid capsule VIZ Rod. X r/j.. ~ -9-+ Resistive _..., - Capacitive o. - Mark IT thermistor***. x ifj. 9. carbon () aneroid MICROSONDE () () capsule * The value in the parentheses under 'time constant' is the ventilation speed(m/s). ** A set of three thermistors is installed. ***A set of three thermistors (upper row) and an additional thermistor (lower row) are installed.

37 Table The observational programme fulfilment Flight Release(UTC) RS- RS-9 RS-N RS-LH IS-A- IS-A- llarkn No. HS L li!crosonde (JPl) (JP) (FNl. FN) CFN) CAR!) (AR.AR) (VIZ, YZ. VZ) Date Time m in hp a m in hp a m in hp a m in hp a m in hp a m in hp a min hp a FEB. : : : : : : : : : I : : : : : : : : : : : : G : : : : 9... loo : : : : : loo : MAR. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : :

38 Table Numbers of launches and successful flights System Total OOUTC UTC UTC UTC JP /9/7 JP 9 9 FN / / FN FN AR /997 AR 7// / AR /9 / VIZ / 9 9 /// VZ 9 9 / VZ Note : Number in each column show the number of launch I the number of flight reaching hpa I hpa I hpa. Table Pressure categories used in the comparison of simultaneous measurements Pressure level Pressure range

39 Table Simultaneous temperature comparisons between the link radiosondes of the phase IV and the same radiosonde models participating in the Phase Ill (unit:oc) Approx. Nighttime Midday Morning/Afternoon press. (hpa) Phase Phase Phase Phase Phase Phase m N m N m N I. -. o I / / I -I I / I. -. Phase m "Vaisala RS-N" - "AIR-IS-A-" Phase N "Vaisala RS-N"CFN) - "AIR-IS-A-HS"CAR) Table 7 Simultaneous pressure comparisons between the link radiosondes of the phase IV and the same radiosonde models participating in the Phase Ill (unit:hpa) Approx. Night time Midday Morning/Afternoon press. (hpa) Phase Phase Phase Phase Phase Phase m N m N m N o I I / / I I. o / / Phase m "Vaisala RS-N" - "AIR-IS-A-" Phase N "Vaisala RS-N"(FN) - "AIR-IS-A-HS"(AR) --

40 Table Simultaneous geopotential height comparisons between the link radiosondes of the phase IV and the same radiosonde models participating in the Phase Ill (unit: m) Approx. Nighttime Midday Morning/Afternoon press. (hpa) Phase Phase Phase Phase Phase Phase m N m N m N - 7 I I I 7 7 I I I I / - Phase m "Vaisala RS-N" - "AIR- IS-A-" Phase N "Vaisala RS-N"CFN) - "AIR-IS-A-HS"CAR) --

41 Figures Fig.l Rates of ascent of radiosondes. Fig..a Differences of temperature based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations oftemperature differences based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. Fig..a Differences of temperature based on simultaneous data for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of temperature differences based on simultaneous data for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. Fig..a Differences of temperature based on simultaneous data for JP, JP, AR and VIZ in the morning/afternoon ( and UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of temperature differences based on simultaneous data for JP, JP, AR and VIZ in the morning/afternoon ( and UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. Fig.. Vertical profiles of temperature obtained at two-second intervals at UTC on 7 February 99. Figures on the right side of the profiles denote obtained temperature values (degrees C). Fig.. Vertical profiles ofrelative humidity obtained at two-second intervals at UTC on 7 February 99. Figures on the right side of the profiles denote obtained relative humidity values(%). Fig..a Differences of pressure based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of pressure differences based on simultaneous data for JPl, JP, AR and VIZ in the night time (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

42 Fig..a Same as Fig..a, for the midday (UTC). Fig..b Same as Fig..b, for the midday (UTC). Fig..a Differences of geopotential height based on simultaneous data for JP, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FN and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of geopotential height differences based on simultaneous data for JP, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FN and AR. See text for details of the figures in the attached table. Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. Fig..a Differences of geopotential height based on simultaneous data for JP, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FN and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of geopotential height differences based on simultaneous data for JP, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. Fig.. Differences of relative humidity plotted against the humidity ranges, based on simultaneous data for JP, JP, FN, AR and VIZ for the temperature range between - and degrees C. The reference is the average of FN and ARl. See text for details of the figures in the attached table. Fig.. Standard deviations of relative humidity plotted against the humidity ranges, based on simultaneous data for JP, JP, FN, AR and VIZ for the temperature range between - and degrees C. The reference is the average of FN and ARl. See text for details of the figures in the attached table. Fig. 7 Vertical profiles of relative humidity obtained at one-minute intervals at UTC on March 99. Figures on the right side of the profiles denote obtained relative humidity values(%). Fig.S.l Differences of relative humidity plotted against the temperature ranges, based on simultaneous data for JP, JP, FN, AR and VIZ for the relative humidity range between and %. The reference is the average of FN and ARl. See text for details of the figures in the attached table. Fig.. Standard deviations of relative humidity plotted against the temperature ranges, based on simultaneous data for JPl, JP, FN, AR and VIZ for the relative humidity range between and %. The reference is the average of FNl and ARl. See text for details of the figures in the attached table. -7-

43 Fig.9 Vertical profiles of relative humidity obtained at one-minute intervals at UTC on March 99. Figures on the right side of the profiles denote obtained relative humidity values (%). Fig.lO.la Differences of wind speed with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. Fig.lO.lb Standard deviations of wind speed differences with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. Fig.lO.lc Same as Fig..b, with respect to JP. Fig..a Differences of wind direction with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. Fig..b Standard deviations of wind direction differences with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. Fig..c Same as Fig..b, with respect to JP. Fig.ll.l Scatter diagram (upper) and histograms (lower) of differences of wind components for JP with respect to FN in the pressure range between hpa and hpa. Winds from the east and from the north are taken to be positive. The unit of wind components is mjs. Fig.. Same as Fig.., for JP. Fig.. Same as Fig.., for FNl. Fig.. Same as Fig.., for ARl. Fig.. Same as Fig.., for AR. Fig.. Same as Fig.l., for VIZ. Fig.. Amount of the -thermistor correction for the AIR IS-A-L radiosonde(ar) and the VIZ Markll MICROSONDE(VZ) in the nighttime (UTC). Figures on the right side of the profile denote the temperature differences (degrees C) and the number of data for each pressure range. Fig.. Same as Fig.., in the midday (UTC). Fig.. Same as Fig.., in the morning/afternoon ( and UTC). Fig..a Vertical profiles of differences of temperatures without the -thermistor correction for the flight at UTC on 7 February 99. The reference (REF) is the average of FN and ARl. Figures on the right side of the profiles denote the temperature differences (degrees C). Fig..b Same as Fig..a, for the flight at UTC on March 99. Fig..a Vertical profiles of differences qf temperatures with the -thermistor correction for the flight at UTC on 7 February 99. The reference (REF) is the average of FN and ARl. Figures on the right side of the profiles denote the temperature differences (degrees C). Fig..b Same as Fig..a, for the flight at UTC on March

44 Fig..a Differences of temperature at standard pressure levels for JPl, JP, ARl, and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of temperature differences at standard pressure levels for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig.l.a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. Fig..a Differences of temperature at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations oftemperature differences at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig.l.a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig.l.b, for AR, AR, VZ, VZ and FN. Fig..a Differences of geopotential height at standard pressure levels for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of geopotential height differences at standard pressure levels for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig.l.a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig.l.lb, for AR, AR, VZ, VZ and FN. Fig..a Differences of geopotential height at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..b Standard deviations of geopotential height differences at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. Fig..c Same as Fig.l.a, for AR, AR, VZ, VZ and FN. Fig..d Same as Fig.l.b, for AR, AR, VZ, VZ and FN. Fig.. Temporal variations of tropopause heights. The points indicating the first tropopause heights and those indicating the second tropopause heights reported from FNl are linked by solid lines, respectively. -9-

45 Fig.. Vertical profiles of temperature from TEMP messages at UTC on February 99. The tropopause level reported from each radiosonde system is indicated by a filled circle within the profile, with the name of the system on the right side. --

46 hp a """'''. """"""""". 7 '...;... '... ' '... ~... '... I "."...""..."."." :..""'".""...;. '""... ""' "... ~! ;.:-J~., l... i ""''''''''''f".... i o... :. T. ;. :... : :... ~~..i.. ~ ~=-... ~.. ~~a~~c~...;... j...:-..,,...,.. ~;;.~,,S,/.!raor.~. : : : : ;.., : : : !' "! !... '" >~t ll'" i HI~'I.Ir e ::'""''~~ : :. : :. r, : ;. :\ :... I ~ l m/s Rate of ascent Fig.l Rates of ascent of radiosondes. --

47 Consistent differences Category: Z 7]'.. ~<~:.;~''' -. \;,. ::! zol.. :::. "::::::. ~tz~.:-..,. Temperature r... r :.:..:p... \, ; tl ',,,,, ; f :. /I /!..! : : \'"~. \ / l i :. t r;:j... :......, :... ;... '! ~ so[......; 7!....,... ;......»; ~~/ :.. '''.. ;.. :.. $ D "'''' ': : : \\ j j j j.!\!\./ j: i "...!,~ "" ". ",.![.'''''''''[''''',.,,,, ~~''' ''',, i ~ : i I ': \l! r ~! : ', i '"""".,... ; !' " "'"""" i: : 'l,i:ji T oli i.., li : t \d I i soo!....!... ~.. + : : \ "ilji :; : : lj ~~~\',I! " ; : I, /<.\. 7: ~! "''''""'''''''l]t~ " : I li/f\ 9!.."""'...,...,... : " 'i/'lr,iql'... ):tf!~......l~;;"'j;:? ' ' ~.. : '''''''''' : : lo:t.=&j.!. =~-~~="==~-... ~~ -...,, Difference of temperature ( oc )... ;. : :... ;.. : REF FNl ARl JPl JP AR VIZ > o l - l REF - FNl V - ARl T - JPl X - JP A - AR A - VIZ Fig..la Differences of temperature based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

48 Standard deviations Category: Z Temperature 7~... :-.. n>~ [\\~- :... ~-~~->~-~.... I! j / ~ \ \ '~,:;.--~- -...: : \ REF FNl ARl JPl JP AR VIZ '''''.'. :. '' : " '. :. lj I: I///:..., "!"'". li i j./..// >/ j sor... r :-\.i\' r ~... : I:' I' I : il I, lj' ' ' 7lr F:nrt ~:... < W.. t Tff / Y.i!/i' li \ J, I l ~.. W:t-ll ':F'\ \ oo~... I.L. i~~\.:... l'i ' (! / ill!..:l }: //,l. ". ~ ' ~"' "f"'t;\'i~.:"" ' "'... '' "'~" ' : ~~ I :, '''i;;; : :. ~., I,,,,,,,,,,,,, l ::: ~~' ; : : ll : '\ \. \... : ~ t..o.~---~... =-..;,.,.-==---=--+ i.... Standard deviation of temperature ( oc ) "- REF c FNl V - ARl V - JP X - JP ~ - AR.;_ - VIZ Fig..lb Standard deviations of temperature differences based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the aver.age of FNl and ARL See text for details of the figures in the attached table. --

49 Consistent differences Category: Z,!, O'l~ :...,::: ~ <-.:~..-.;::~.. :~~:.::_'.l:lt'.:._ -.. ~..::::::...:..:: !... tr Temperature,,:.!.. J!V' : :: : \ =t:.. IJ / ~,.: ~ ::~, I~\ {\i( '!'... :.' "~\ "t t't r-.,/p':r (... :... '!" i... :It;i'~.~... i=l'...,: : '!), i. ~ ~ ~ \\)'./ ~ : ~ '~. i / ~ 7,.....,...;... ;... ff~~...;.... : ~ ~- {l I J I! il,...,...,... j... w/~ : :lv'lll!... :.... J+l~ I! ol\...,. I'... \!i \ : ~~:: :,- l irl,,rrr...,...,... ""'"'"...,.. r' < : :!'...,) :< : ' ~ " < '''! ',. l!tj!"...: ;......; Mtll......,....,...,.. l' : : : l'i\\\ sool... j... ~...,... t:f~...,...,.....,. I! : ilih!! :. i itw!...,...; 7 :..... r......;...!... 'ft:r...!:. ~. lilt!\ 9jj""'"""':""'"'' ;... "'!'''"'"ffti... = r ' ' ' I hi l : : : : l.;\l:.r,t----~ H -.o o.o. Difference of temperature ( oc ) - REF : " ' " ~ r : '... '..... ' : r!... :... : : REF FN ARl AR AR VZ VZ FN l - l FNl ~ - ARl T - AR x - AR ~ - VZ ~ - VZ w - FN loo loo Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. --

50 Standard deviations Category: Z Temperature REF FNl ARl AR AR VZ VZ FN '; l ;.. 7 loo... ;. 9 9.l l 7.o l... ;. '"'... ~ " ".....;... l l 9 l. 7 7 l 9 9 l Standard deviation of temperature ( oc )... a - REF u - FNl ~ - ARl T - AR x - AR ~ - VZ ~ - VZ u - FN Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. --

51 Consistent differences Category: Z Temperature REF FNl ARl JPl JP AR VIZ,:~'q~ ' (\,+7:\.. ([~ '"""'...,...,..,...,... ".,,,, ~...,... t,;..,...,.... /r. " '#-'~''I" '!. 7 loo loo :... \ : "!"" ". i"". ~ ' I : ' ~.:.). ""'\".,/.. / ool: !,,,... :,,,... t;t.,... :.. ~ '..i I'..., ~ ~~ i.x... :::t... rt r.... V : : : : : \\ TV ~~ [ ~ p (ll ':. '". ""!'... i... """!."' Mr.. ~f.. f";"... ;. """"'.., :.. l.'l ~~r. I : ; : \\, lj I...:... :,"""'..(...'!'... '":' '""~t':lh.,..., : i i : li I f, 7,...!...!...,... i#..,l..,.,...:..... r... r.. 9 ' ~\J...,. :,... li : ~ il'l- i / : : J.i&..~J -... Difference of temperature ( oc ) : o REF!:l - FNl "~ - ARl '~" - JPl x - JP " - AR " - VIZ Fig..a Differences of temperature based on simultaneous data for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

52 Standard deviations Category: Z Temperature REF FNl ARl JPl JP AR VIZ ~ '... ~ '"'"' ' ' '.. ' :' '.. '. '. '. ~ ' ' ~ " " ". ' " ~ ".. l 7. Standard deviation of temperature ( C ) - REF w - FNl V - ARl T - JPl X - JP ~ - AR ~ - VIZ Fig..b Standard deviations of temperature differences based on simultaneous data for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. -7-

53 Consistent differences Category: Z Temperature REF FNl ARl AR AR VZ VZ FN Y > > : Difference of temperature ( oc ) REF w - FNl "" - ARl "' - AR :' - AR ~;,. - VZ.,~. - VZ Lll - FN Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. --

54 Standard deviations Category: Z Temperature REF FNl ARl AR AR VZ VZ FN l ;.. "~. '.. '.! '....; '" i ; Standard deviation of temperature ( oc ) l ll - REF - FNl 7 - ARl " - AR : : - AR t.. - VZ " - VZ :n - FN Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. -9-

55 ... ".. ;... }. ri Consistent differences Category: OOZ + Z Temperature REF FNl ARl JP JP AR VIZ 7f,,,:'\..... : '!,"". "'..;_...):!"!!li \,"... : ")(... :...:.../... :.. :/' ~~... : \... ::.... <,r~. r' ~.. :t.c:.:....:!.. I!;.. 7:.. ;<:"< ~ t \ / ~ ~ ' \,:... r t.../.--- :.~:.'. '...: >>''f:_... ;...,,,..(.....).../.. 't-, fj... j /~./l.!.:_... ;... _,...:_...,-\.:...,... i. T~ /r H :...\. ~':!',!,...!:" ;....,...;.....,._i,,;,,,,,,.l. ~ ' '' il......[.~~...,..!... :.~i... ; \T ;?......_ ~! ; \k l,../ I solt "'"' ' -'- )i jl..- :;.& '... :! ~..... Tur::::: r r ir: i 7o[.... ; ;... \l. \ Tt l _r_;f-.....~... ;... ~ ~... +ll 'i>"'"'!: ~V.\ \ l!.',.. j; 'r I f' l / oil-... ;. ;..:.. ~- M, l! ~ \':!I : : \[, ).!! oo[..... t,_... ;... r -~?... +# 'i J; ~ \l : : lj I ~~ '"'' I.,... y.... ~\ I V,, :. : ~ r \. l I i!:. : J. / ll i ( "!"'... ;... :Jl\/Ttr-.. ' I " [...,..., i: : ;,. I,I ;. \.' I I oo:... :....;... :... \ T"'T"' gooli...,...!... i... f-~l i~ : : (/..~~ l ; : I il I;!.: ) ::-.~-'i--.;...-=="=~-~ : i: -... j; Difference of temperature ( oc ) l REF!:! - FNl "' - AR 'f - JPl ;.: - JP ~:. - AR..!. - VIZ Fig..a Differences of temperature based on simultaneous data for JPl, JP, AR and VIZ in the morning/afternoon ( and UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

56 Standard deviations Category: OOZ + Z Temperature REF FNl ARl JPl JP AR VIZ o >~ - REF :: - FNl "' - ARl.,. - JPl :.: - JP "- - AR "- - VIZ Fig..b Standard deviations of temperature differences based on simultaneous data for JPl, JP, AR and VIZ in the morning/afternoon ( and UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

57 Consistent differences Category: OOZ + Z Temperature 7t...,....'.. t.;.. p '{f. ' :.,.,.' 7.: : >.../:::~::::~:~/!... ~// I.:...,... I V ij r. ) if... ;.,..,._, :.!,: :...;... '!;i i oli. E... T...,.... i:'...,.... I) ' i ~ I /. i. ~! :... I... :.. J.:J.. l:.l+i.. :.+. 7';,... ~H + y I...,.... ::J!,~\~.. ~--)+~~~::: it.t:::::~..,.../.. ol!...!...:. '"" ",... i :. : ',', i!i! : j' :.!.. \~rf,ll_l.. il,!l,....,;.t.. j :... : ~lj J I i : : \ ii : ' :... :... i... ~ +~... j... :..... r : : : \\//:. ""...,.,. ~ <t. I: ' \ i ; ~ :,Jii i,'... :... I... ~~ r r.... J'....,. 7':...: 9':... T'... '... '... /\ti ' I '.. : : :. ~ I : -...\:.f..:~<t---~=.=~---;. : f,l A :~<.. Difference of temperature ( oc ) REF FNl ARl AR AR VZ VZ FN o l REF!:i - FN 7 - AR.., - AR :' - AR "' - VZ.>. - VZ m - FN Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. --

58 Standard deviations Category: OOZ + Z Temperature REF FNl ARl AR AR VZ VZ FN ; : > : " 9... ;. ": "~ " " " "... " 9 ""j'''"... ;......,.." ~ j "'" ""?'....; ; ;... """ '""" Standard deviation of temperature ( oc ). ii - REF - FNl "' - ARl "' - AR ': - AR "' - VZ -' - VZ m - FN Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. --

59 Flight Temperature UTC a: or j: 7:" r: r... :.,,,,,'.. ;... :... ;... :... : : '"l. -.. <... ;... :=: V o. '. ~....;.. ' ' ' ' '...: ' '.(... '.' ' ' '..... FNl ARl JPl JP l l. 7 l l l l. l l. l. 9 l. l.. 9 l. l. 9. l.. 9. l. l l l l l l l l l l l l l l.. VIZ l.. 7 l l -. l -. l l. l Temperature ( oc ) ;s - FNl " - ARl "~ - JPl Y - JP :.: - VIZ Fig.. Vertical profiles of temperature obtained at two-second intervals at UTC on 7 February 99. Figures on the right side of the profiles denote obtained temperature values (degrees C). --

60 Flight Humidity UTC a: at I 7:!".. i I 7 :!..! ' 7: j... i i 7 :"". I 7: " ' 7: O! l : i... ;.. : "'""':.. :! i.... ;... j..... (... : i :... ;. :!." ': ' " ' "..;.. ".. ' ~ : '... j! 7 Humidity(%)...;.. ~ '.. : FNl ARl JPl JP : : '... ~ ' :.. :.. '.! ' ' : -: l : l l l VIZ loo loo loo loo loo loo loo loo loo loo loo loo loo loo!!i - FNl - ARl "' - JPl " - JP x - VIZ Fig.. Vertical profiles of relative humidity obtained at two-second intervals at UTC on 7 February 99. Figures on the right side of the profiles denote obtained relative humidity values (%). --

61 Consistent differences Category: Z,i j'... T... ;... ].. :... ~ '.~.:.::.::::.:...-..::.,.~[~.:,,,.:.-.,!~\ : '....,... Pressure.. lr..,)..:-.'..\.. ~ :~r.:.: ~? ; : :... V... '! ' ;... :...;...,......,...,. ~ -~ I : : : :,I :\, \i I j. i'\ :... ~... <!... :.. ~.. f i x.. ~ :,..... ;... ~.....,:...,..., ',v I :J~; : l i: -;-: i: {." REF FNl ARl JPl JP AR VIZ ;.. '"':'" !... oo r : : :.. :..,,,,,,. \.\. '.'. '.'. /t<-~j...: -~: ::-'.'.. :...).:.:..: '"'...,.. L... t".,...,....:... ' ~_), /:... '.!. ->.c~ < ~ : : -~ -. '.. ~ '... :.. '.. ' ' ' : : ,,,...:;!:. i:' -~-::=~ :=:..~====-=-==~! ! Difference of pressure (hpa) ~ - REF D - FNl V - ARl T - JPl X - JP!:. - AR ~ - VIZ Fig..a Differences of pressure based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

62 Standard deviations Category: Z Pressure REF FNl ARl JPl JP AR VIZ l 9 9 l 7 l 9 9 l l l l l Standard deviation of pressure (hpa)!! - REF Cl - FNl "' - ARl "~' - JPl ;.: - JP L - AR "' - VIZ Fig..b Standard deviations of pressure differences based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. -7-

63 Consistent differences Category: Z Pressure REF FNl ARl JPl JP AR VIZ '.. ;.... ; o : :. : ; o o Difference of pressure (hpa) ~ - REF c - FNl V - ARl T - JPl X - JP ~ - AR A - VIZ Fig..a Same as Fig..a, for the midday (UTC). --

64 Standard deviations Category: Z Pressure REF FNl ARl JPl JP AR VIZ ~ ::nw~: ::,, ~'.ij.":""~""":.;.{-.,...,...,...,...,...,.. H \ ~ ~. : 'j!. ' ' ~Art.. '.. l*.. i... o~~~....f'~.. HI...\ h.r...: ,......,...,.,.. ~ ~..., , l ~I L i!i \ ; 7...,.!~"''!\'".:t" :x,... " : , : 'ii\,.....,...\. :\ : ~...,..,... q *.., r..... ]... :..., '.;.. '. '.;. '.. ' { '. ' ' ~'. '. ' ~'.. ' ~'. ' " ~". " : ' '' ~,'" ".. ;. ".. ;..... :'\. I '.. ~ :t : ~," ' " ".. ~.. ".....;....! '"..; : ~ ~-.~ ~.~-- _ ~.. : : ~>~':}:_::> ~... l / :...-- r. looo~~;;...;...x.;;.;;:.=~===" Y=~====~=~ o.. o. o.s so Standard deviation of pressure (hpa) - REF - FNl ~ - ARl T - JPl X - JP A - AR ~ - VIZ Fig..b Same as Fig..b, for the midday (UTC). -9-

65 Consistent differences Category: Z Geopotential REF FNl ARl JPl JP AR VIZ ; :. "'"~"'" ;... {" Difference of geopotential (m)!i - REF Cl - FNl "'~ - ARl " - JPl >= - JP t. - AR " - VIZ Fig..la Differences of geopotential height based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

66 Standard deviations Category: Z Geopotential REF FNl ARl JPl JP AR VIZ... /l / : :rr ~ i '''''''') : : r!... ;.. i... ; ll ;..... j... : 7 9 : : :.;...,... ; ;.. :! r :... ;... ~.... ).. -=...,...; !.. '. ' :... : :.. j. : ,,,,,,,! : Standard deviation of geopotential (m) "- REF FNl v - ARl v - JPl ': - JP "- - AR " - VIZ Fig..lb Standard deviations of geopotential height differences based on simultaneous data for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

67 Consistent differences Category: Z Geopotential REF FN ARl AR AR VZ VZ FN 7t ~.::.<-~,~,,}~:~ ~_,!. "!... -~. :;.>'':i>t::! ,.. "'<;;;:~r '~... it:.. r_... -~>". <:.~ _-._... r,, ,..,... " ":..., '. _ ' ' ' ' ',,!,!... "......"'<... ~ "' ""!"""... ~..!D_... _~:;~~.~_. :~.:: _-...'"'".~:.. _;:::;:::::>~ :~:-.!... >i l././ /' r-rr -t...; ~- ~- >-~\-.: t ~-~.. / : I., I I \. I.., ,.... \\ +! ~~~-l... ~. i. ~ \ i! l 7"" t...: r"..,.. : : ~r. --:......!. t'.. t n..;.... I '!, : :. I!~~!. ".. ".. -~ ~. : ;... I ~!\ I I i ~ i ~! il i fll ~ "" I.;... ~... +t.!ii '... j I ~ \ \ I I ~ j :. \,ji, o,... T... '.. \ ;... i... I ' ' : ~!lfl ool ;... -\t...; 7ool I : : I i I :... il...!,... ~.~-~ l : Yl J : i\ I : lj... l_... ~ : : ""'f"".!... ; 9,. r... r..., :... ;... :... fi...,...:......! I! i ~: ===-----~-=====~~ I -oo o zoo oo Difference of geopotential (m) ;....; loo lb loo lob - - loo lob l ~ - REF - FNl " - AR ~ - AR x - AR ~ - VZ A - VZ m - FN Fig.S.lc Same as Fig..la, for AR, AR, VZ, VZ and FN. --

68 Standard deviations Category: Z Geopotential REF FNl ARl AR AR VZ VZ FN 7~... = x~.. <;::: ~ :.:::. : \..... l :\. :./ ot.,.. rt, \.o:.:... [ :A!... ::i:~>- rr. t<f ""f)/:... "'(. : t B loo ~{/l, &-f'lr:fl...,... I ~/,.:/ j? sot : M... i! I ~~/ ~!I n :V 7 ;;/lc -'.;. F li u : t looitlff..,...!ilil ~f' "!!I if ~" "!'... ITH... j '' : MJ."... : !... :! : mi-""'!.;... llii llli. 7!.l!i... :.; [lf 'ii!i Ill 9~""""!"""'...;...:.! Ill > i,,,,. I,,,,.,... ;. : i "..;.;...! ' ~.. '.. '. '.!... '... l~ =----= =---====-~-=~! Standard deviation of geopotential (m) lob loo i! - REF - FNl "' - ARl T - AR x - AR "- - VZ ~ - VZ!!l - FN Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. --

69 ------~---l ~i. ---~-~--=~"'==-f>~ Consistent differences Category: Z.i. ~:r; Geopotent ial r<.~'*~v~!""":.:.... ~.:.....:.. c;~:... ;.::-:r ~... I :\. I I ll.\i. i"" :"""".. (~.. ""'... :.. ~..., ,.(t,r.. :.....;... :: :... ' \t \jfj f ', \ n ~ \...!?Oi,...,...,...,.....:~.~... ]~... L.. ' ' ~!I! m. v ooi.,. I!'...,... I '..,.!..,..,.. :..,:~:~: "'"'"...!.. i "'~ T \lilt.!...,. +~wt '"''.! + ~;:. I \ tli J.... \~J~. ''""'...,... : \l!l, , ~~... ""...,.. 7 i :.,... i. iti rj gool ".,...,... :.. m... l j I!)I! I! ""' ')'... ; ;....;... REF FNl ARl JPl JP AR VIZ lll l Difference of geopotential (m) - REF - FNl "' - ARl "' - JPl x - JP " - AR "' - VIZ Fig..a Differences of geopotential height based on simultaneous data for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

70 Standard deviations Category: Z Geopotential i?rr... t... 'TT... "': ,. ~):..:.:.:~, H I! : i '.~ ~---- ~ "/';.h "ily+ ".... ~,.>>"~~ 7 :<-:~~~ " ~.f...!...: t.~. : :. :. ')::~;;f''' "..." " " "... " ~J..... i<'. :... :.... ~..... H \ /~: ~.?:;... I! '\...:,./:.... li'.t-..y "i! : V :/;/ ' rr"ti"h" :....,... il 7[ ; ;tr /~l M!. ti..,i! i ' I: ~f~h"""......,. " "j.,, J,ij!/ :. B'.!ill/ ~ il i!ll :. iht.' t" ; ".. :. zoom..!... r...;..., o~ml~'l..!... ~..... ~ I') : l ~ ~i ~,!fl : : if'" I"'""' I'... '?oofi~~~,l... :... :.., ~ 9"""! "",,." ".;.... ~. : '''''' : :.;. : :... ; " ~" ' "... ) ' " " " ' ) : : ''.. ;... : lj! \! looo!~ch.~ ~=~-----=-W~ I oo zoo oo o soo Standard deviation of geopotential (m) - REF - FNl ~ - ARl T - JPl X - JP L - AR ~ - VIZ REF FNl ARl JPl JP AR VIZ 9 B B B B BO B BB B B B Fig..b Standard deviations of geopotential height differences based on simultaneous data for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARL See text for details of the figures in the attached table. --

71 Consistent differences Category: Z! if '... ;;.:....:{;. /: / /' ~/.. :.. :... : Geopotential REF FNl ARl AR AR VZ VZ FN : Difference of geopotential (m) & - REF w - FNl ~ - ARl T - AR x - AR ~ - VZ ~ - VZ z - FN Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. --

72 Standard deviations Category: Z Geopotential REF FNl ARl AR AR VZ VZ FN 7-l.. '"'~'! '"" y'!"" "": "':\.:..,,,...,: ~ '" i: / / : f :... ~ ~ H ll..,:.. '"V.:!...,..... '.t.::.:..,'"' '.... 'I V : i : v... ;... = :! ::~~Yvr ~.. ~ -!... /.:... i... :!! :! :... i.. ri i./ j // })I, ~ ~ i SO["'f' t...; ,...;. l)ii i'i "!i ':?oi* -,f ~ i :...,.,.. li Hi l i : '!Ill t i oo~ f...:... -:-...:..... ITw,,,!! I ill *7~".,...,.. '..,... :'...! J.~ illli ltft '! :.. :..!! ~'" i...,... '.,.. '.....! !. '.. ~~.. '"!"" ".~...;...,... '''...;..... ll.!!! ~ : : 7[i~ " :.. ~!.. :...,.,..., ~ ) : : : ~ ~ 9~"""'!"'" '"('". :'...,... :... ;.... looof : too. I Standard deviation of geopotential (m) !!! - REF FNl v - ARl ~ - AR x - AR ~ - VZ ~ - VZ ~ - FN Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. -7-

73 Consistent differences Humidity Category : OOZ + Z + Z + Z Temperature : - oc - oc %~,_,... :... :... :... : FNl.::~ -.. ' :.. :ofn. ---'!' Q ~------~~~~~~~st~?;~:-~~~>;:==~t~-~--a~~~~~ ~-- :.o.vrz - :.. Ill 7 9% Humidity FN FN AR AR JP JP VIZ -7.9 ( 9) -. ( 7) o. ( 9). ( 9).(9) -. ( ) -. ( ). 9 ( ). ( ) -. ( ) 7.9 ( 9) I. ( 7) -. ( 9) -. ( 9) -. c 9). ( ). ( ) -. ( ) -. ( ) o. 9 ( ) 7. ( 7) -.(9) -. ( ) -. ( ) -. ( 9) -. ( 9) -. ( ). ( 9) -. ( 9) -. ( 9) -. ( ) -. ( ) -. 9 ( ). ( ). ( ) Fig.. Differences of relative humidity plotted against the humidity ranges, based on simultaneous data for JPl, JP, FN, AR and VIZ for the temperature range between - and degrees C. The reference is the average of FNl and ARl. See text for details of the figures in the attached table. --

74 Standard deviations Humidity Category OOZ + Z + Z + Z Temperature : - c "C! --~- -~~.""---- : FN : ~-... ::::,...---~~ / -, ----.~- : Cl FN s%7~~... : >, :>~:~~,_ :... >>.. :::~~~~~~~:~:~<:~.[... ==I====~:~=~ ' // ]"'''< "'io====:-:t>--"~_- :~:~ / ', --- 'l(.. ~~~~~~~q" VIZ ;...;...;... ;...; : : : % Humidity FN. 7 ( 9). ( 7). ( 9). 9 ( 9). ( 9) FN. ( ). ( ). ( ). ( ). ( ) AR. 7 ( 9). ( 7). ( 9).9 ( 9).(9) AR. 7 ( ). ( ). 7 ( ). ( ). ( ) JP!. ( 7). ( 9). ( ). ( ). 7 ( 9) JP. ( 9). ( ). ( 9). 7 ( 9). ( 9) VIZ. ( ). ( ). ( ). ( ). ( ) Fig.. Standard deviations of relative humidity plotted against the humidity ranges, based on simultaneous data for JPl, JP, FN, AR and VIZ for the temperature range between - and degrees C. The reference is the average of FNl and ARl. See text for details of the figures in the attached table. -9-

75 Flight Humidity 99.. UTC ARl FNl FN JPl JP VIZ,.,!" '...,...,. ~ i ' ' I """"'...;... i... "'"i'" i' I >.., : '"'"""i.. :..., I... ~ '.'.'...'.!.' '...'.'. ' I! "'"""' :...! >. :! I F =~========~====~==~==~~==~~~ -... ~?: ll loo a Humidity (%) - ARl " - FNl "' - FN ': - JPl - JP - VIZ Fig.7 Vertical profiles of relative humidity obtained at one-minute intervals at UTC on March 99. Figures on the right side of the profiles denote obtained relative humidity values (% ). -7-

76 Consistent differences Humidity Category OOZ + Z + Z + Z Humidity % ~ % -, C Temperature FN -. () -. ( ) -. ( ) -. ( ) -. ( ) -. ( ) FN -. () -. ( 77) -. ( ) -. ( ). ( ) o. ( ) AR. (). ( ). ( ) o. ( ). ( ). ( ) AR. ( 7). ( 7). ( ). ( 7). 7 ( 9). o. ( ) JP. ( ). ( ) -. ( 7) -. ( ) -. ( ) -. ( ) JP -7. ( 9) -. ( ) -.7 ( ) -. 7 ( ) -. ( ) -. ( ) VIZ -. ( 9) -. ( ) -. ( 7) -. ( ) l. ( 7) -. ( ) Fig.. Differences of relative humidity plotted against the temperature ranges, based on simultaneous data for JPl, JP, FN, AR and VIZ for the relative humidity range between and %. The reference is the average of FNl and ARl. See text for details of the figures in the attached table. -7-

77 Standard deviations Humidity Category OOZ + Z + Z + Z Humidity %,.._ % :FN :ofn Temperature.. C FNI. (). ( ).().9 ( ) FN. ().9 ( 77). 7 ( ).9 ( ) ARI. (). ( ). ( ). 9 ( ) AR. ( 7). ( 7). ( ). ( 7) JPI. ( ).9 ( ). ( 7). ( ) JP. 7 ( 9). ( ). ( ). ( ) VIZ. ( 9). 7 ( ). ( 7). ( ). ( ). 9 ( ). ( ). ( 9). ( ). ( ). ( 7). ( ). 7 ( ). ( ). ( ). ( ). ( ). ( ID Fig.. Standard deviations of relative humidity plotted against the temperature ranges, based on simultaneous data for JPl, JP, FN, AR and VIZ for the relative humidity range between and %. The reference is the average of FNl and ARl. See text for details of the figures in the attached table. -7-

78 Flight Humidity 99.. UTC ARl AR FN JPl JP VIZ '.! '. '...!..... : : ' ' '..!.. '. :,,,,,. '!'' ;...,,, : ! ' ' '. '. ' i...'...'' i 7.'. l... t :!'..' ,,,,,,,,,, :.,,,,,.,,,,, ;.. : i < i i i 7! : i '.. '..'...! :! loo Humidity (%) s - AR o - AR ' - FNl x - JP ~ - JP ~ - VIZ Fig.9 Vertical profiles of relative humidity obtained at one-minute intervals at UTC on March 99. Figures on the right side of the profiles denote obtained relative humidity values (%). -7-

79 Consistent differences Category: OOZ + Z?f. I!. I > ''''...,..., I "" "('....,... I. ". '.! I.. (...:...:...,,, Velocity + Z + Z :... FN ARl JPl JP AR VIZ FNl..o ' ol ~ :! i!'... ;... < '... ;... : '... ''.,,''.:... l.j'r :..._ ~ : o oo!! I 7i' j < ; Difference of wind speed (rn!s) - FN - ARl v - JPl T - JP x - AR ~ - VIZ A - FNl Fig.lO.la Differences of wind speed with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. -7-

80 Standard deviations Category: OOZ + Z Velocity + Z + Z FN ARl JPl JP AR VIZ FNl...; 'i "..; o o l... B. 9 7 lob Standard deviation of wind speed (rn!s) ~ - FN c ARl V - JPl V - JP X - AR ~ - VIZ ~ - FNl Fig.lO.lb Standard deviations of wind speed differences with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. -7-

81 Standard deviations Category: OOZ + Z Velocity + Z + Z JP ARl JPl FN AR VIZ FNl = , I,, : ! ! : (... j.. :.. : : '''''''I,,,,,,.;..... ;.... j ~ Standard deviation of wind speed (m/s) V - JP Cl ARl 7 - JPl m - FN :o: - AR "' - VIZ.;, - FNl Fig.lO.lc Same as Fig.lO.lb, with respect to JP. -7-

82 Consistent differences Direction Category: OOZ + Z + Z + Z j,?l(~ ~>~j ;...;,,,, i... i......;...; :... ;... ;... :... ;... : ' '. ' i. '. '.. ~. '. ' '.. ': : '...,' "!'' 't<(~ttll"' t "' "" "; ""'..,. '' J:\~~ l"i"" ""',.. \,.,,,, I..... ~... r.....;... <... : : '''' i : : i < : '~... '... : ~... '... : :... '.. ' :.,... r..., FN ARl JPl JP AR VIZ FNl : : '' :,,,,,,. '. :'.. ' ' '. ~. ' ' Difference of wind direction (de g) 7 7 ~ - FN c - ARl ~ - JPl V - JP X - AR ~ - VIZ ~ - FNl Fig.l.a Differences of wind direction with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. -77-

83 Standard deviations Category: OOZ + Z 7tl,... ~(\.. )\;:A;,s... f._.: :.:.:.o Direction + Z + Z.. > FN AR JP JP AR VIZ FN :- "'-~::;~~~~~~ C(;; : \ : \~..._ : ',! : :\f'~~~~>j)p : ~'... :...!>l t.'r:. cl<-... T ~ l,jtgt~~~~... : y :....;.... ; :.. -r : : so~...,.,.,"p.':':7....., ~.. 7(;;~~~< : !..... : V/!! ~'... '... ll...;';, Fi" ~."...: "... "... ~ -~ > -. : ~ l' \ : ~( -.,> r.. ~-:--: : : : :!lil!;l. l i)li ~!,tlli Qilr;ilf... :... ;. r : : : :... ; ; ;.... >....; '' :... ;.... ;. ~i.:j;:.,...;l ~ I w ~ w w Standard deviation of wind direction (de g).o o o o o o o o ~ - FN D AR V - JP ~ - JP X - AR ~ - VIZ ~ - FNl Fig..b Standard deviations of wind direction differences with respect to FN, based on simultaneous data. See text for details of the figures in the attached table. -7-

84 Standard deviations Direction Category: OOZ + Z + Z + Z 7t.,,. :,, ' ' ' '"S~~~;: ', l.j.:.:.:.:n," : lo!'f ii.... "..;... I! -... I " " ~ :!' ~"'-. -:- <! ~"' : '\, ~ sorr il 7~r:~f.;:.-~{: :<:-... '.,...,. -:'...,. '..! loowj~ii- '..,. "...,..,.,=r/\ ;ti I!'W (i \ :.... i. ['.f. -;.:~.; ' \t// : : ~,- ;.. : : I! I olln,..!'!i'i. :... ~~-:.._: ~~ ~' : ~!...,, I. --. it ll : : 7~~-.:..,. I,I. '' <t~~~:~:: ! ~~-----.:.; ~--,-_..,... "'! 9oo~- lffr. r :r ':{;~.:.:.; ~ / t -/..,./: : ;.._ r-<t:...o-b.l: - -- =:;} I I.;... : ;,.. ;... ;... ". : " " " " ~ '.. :... : r : ''' : "i ' ' ' :'. ' '. ' ' ~ '. ' : Standard deviation of wind direction (de g) JP ARl JPl FN AR VIZ FNl o i' - JP Cl - ARl V - JPl li - FN :;: - AR L - VIZ.. - FNl Fig.l.c Same as Fig..b, with respect to JP. -79-

85 ooz Z Z Z JPl - FN Pressure:.--. Points: 9 Beyond plot:... ito.. : " -... i '.!. '.! '.... ' '... i :... :... j.... :... j... i....:...!. '"'" : ~.,. ;; )>~~: ;:~i;.; ' ";" :.,:,~fi"'... :.:r..:ji*lll:r.~<.'-i.~;r.~b{.. :~.. ~:... ; :.::l.. :...r.... :::.. :.... :l:r.:......:...! :...]...:. '.".:" " :... ' ~ " ' ~ ~ ".. : i : : : :::...:... :::::::::::::::.::!'{~:~;:::::...:... E-W average:. ; st.deviation: S-N average: -.9; st.deviation: ~.. JPl - FN Pressure:.--. West-East South-North ": : :... UT.:::,~::..: :..: :--. r.. ::::::: i ~...:.:._::., H+.. i,. I l I' ' :.. :--:.:.. :.J.. H I..! rij... Hl i! ll i i i M -'' ; ' ol I I ;lo:n/sec!! i~ll~l i i i I iiiii i Ill.. ;.. ;.; l~.::r.:::: ::'::'::j: l::l::n::: :.;..;..! _;l'o;. ; FTl :!.,,, I,, ; : O:n/ sec Fig.ll.l Scatter diagram (upper) and histograms (lower) of differences of wind components for JPl with respect to FN in the pressure range between hpa and hpa. Winds from the east and from the north are taken to be positive. The unit of wind components is mjs..,..;..; ;..!!.. ;. j I l,..l,..!l l,.. :,.. :l,..,.,..!....!! i : : ' '.... ',.. ',.. ll l,.. l,.,.,;...,,' :,.,;.. ' lq"!''"!f':: i I I I I I.., H!-:- --

86 JP - FN Pressure:.--. Points: Beyond plot: ooz Z Z Z E-W S-N JP - FN Pressure:.--. West-East South-North 9 r: d.. H H)'TT _ilb; ~"!"!'. '':"!" -'' ' Qnjsec Fig.. Same as Fig.ll.l, for JP. --

87 FNl - FN Pressure:.--. Points: Beyond plot: ooz Z Z Z E-W S-N FNl - FN Pressure:.--. West-East 7Ch'"; I...:, Ch,..!'!' :.. ;.. ;.. ; :.. i ;.. ;.: I.,~..!.,..,.,. l :.: ~ i i : ffi. ~ i : i.,.. South-North gfi..:.. : s! 7i i! ":":' $ i i ""': i : : ''"" - ro "'''!!!--H.,... n.. : I/;:..... : ~ ~ ~ Hy H+r~ o On/sec Fig.l. Same as Fig.ll.l, for FNl. --

88 ARl - FN Pressure:.--. ooz Z Z Z Points: Beyond plot: ''' '.... ' i ::::::::::::::. "... :... :...!... ;.... :... i.... :... "" ' I "'......!..... j...:... ;,...:.. =!"" ' ""' '"...:...:..!:..:...;...:.)... -:~ :::: <:.::.. ~ ~)t.jm+~t ;,;_.. ~:.. ; ' :'~~~~.~.. 9 ~ '.. : ~ E-W average:. ; S-N average: -.;. ~... l.. '. ' ', "!. ":.. i ' ' '... :... :. I... I..... I I. I.... '"'":.:;"" "' st.deviation: st.deviation:..7 AR - FN Pressure:.--. West-East q $ : q :.,..,.,..! ' i i l i.;..!.;... ~..!..!..!.j.. i '' South-North -'ln 'i'l I, I, Un/ sec 7d."!"'".i.i.. i.. dl.i.. U.,..,... l I I::;,, d.. H.. d. H q " d! '" zd! : 9'!"[' -'' Jliit~lll ~~ i rill ':.I, o'ir-! Qnjsec Fig.. Same as Fig.ll.l, for ARl. --

89 AR - FN Pressure:..--. Points: 7 Beyond plot: ooz Z Z Z E-W S-N AR - FN Pressure:.--. West-East South-North -'' ' Qnjsec Fig.ll. Same as Fig.ll.l, for AR. --

90 VIZ - FN Pressure:.--. Points: 79 ooz Z Z Z lqm m!... : :... i... i... "'.:... ~.. " : "'...,...!...:...:... : ' ' t~... i.... L... L... i!',,:it,. :. E-W average: S-N average: '.... i ' '.L...!.. : I.. '"' '"""~"... '.; st.deviation:.; st.deviation:.. VIZ - FN Pressure:.--. West-East South-North sd. ;,.... ~ : d. :- :' 9"'"' - '!"'" '...,.,..,. ~..!...;.l, Hm/sec Q"i"!,, "": ".,.. d.! ":..... ~ ~ ;.. "r T m! i! -'' Qnjsec Fig.ll. Same as Fig.ll.l, for VIZ. --

91 Direct differences Category: Z Temperature AR VZ o. 7 o. 9 o. o. o. o.. I o. 7 -o. 9 O. I 9 -o.. I I 9 o.. I 7. o.! o.. I 7 o.. I o.. Temperature correction ( oc ).. I - AR.o. - VZ Fig.l. Amount of the -thermistor correction for the AIR IS-A-L radiosonde(ar) and the VIZ Markii MICROSONDE(VZ) in the nighttime (UTC). Figures on the right side of the profile denote the temperature differences (degrees C) and the number of data for each pressure range. --

92 Direct differences Category: Z Temperature AR VZ o I o Temperature correction ( oc ) o AR... - VZ Fig.. Same as Fig.., in the midday (UTC). -7-

93 Direct differences Category: OOZ + Z Temperature AR VZ. I. I 9. o. 9. o... I I. I Ill o.. l o. o. loo o. o. 9 Temperature correction ( oc ) o. l o. - AR - VZ Fig.. Same as Fig.., in the morning/afternoon ( and UTC). --

94 Flight Differences of temperature UTC 9: :.... : : * f -... ;..... ;.... REF AR VZ...o...o o.....o -.7 -l.s -l l. l.s l a s ' l -. l ,I, A ~ -, l l l. -..o l o l l -. l l l ~. l -. l -. l -,l l l -. -.l -.l -. ~. l ~. -. '. Difference of temperature ( 'C ) - REF - AR ' - VZ Fig..a Vertical profiles of differences of temperatures without the -thermistor correction for the flight at UTC on 7 February 99. The reference (REF) is the average of FN and AR. Figures on the right side of the profiles denote the temperature differences (degrees C). -9-

95 9 r -.. as... f REF AR VZ -.. -,'J l -. -.' -.' -.a ' -. -.' ,...,].,). I 7; '.l.l,.., [... >.,... ss:... "i..o,.., :!:'. ' :..!... )..... ' ; :.. ~.... '" f... ;. '..... i Difference of temperature ( 'C )...,...,....o o -. -., , , o -..o o o REF -AR -vz Fig.l.lb Same as Fig..a, for the flight at UTC on March

96 9 B~~~h t U~~fferences of temperature REF AR VZ, o -..o -. -., -., -...o ' J. -.J J -. J -. (... d.,. ' !.. Go r...,...,... '.'... '.. ~.... '.. -~ -.' -.J J -. J -. J J J ' '.' '.o '.,, so,.. '''"i ""'''' l I "., '' -.l -. ' l -.l : ; ~ l -..o o l -. :... : -.l ' -. l , -.l l -. i of-:..;.,, x....,, _. :.._ l -.l -. l -.l -.l -.l -.l l l -. -.l Difference of temperature ( "C ).. - REF " - AR x - VZ Fig..a Vertical profiles of differences of temperatures with the -thermistor correction for the flight at UTC on 7 February 99. The reference (REF) is the average of FN and AR. Figures on the right side of the profiles denote the temperature differences (degrees C). -9-

97 9 B:~~lo g~lu~efferences of temperature REF AR VZ ' a ' J. -, ( a H H' ( i , ;... : o -. -' = = Difference of temperature ( 'C ) REF "-AR -VZ Fig..b Same as Fig..a, for the flight at UTC on March

98 Consistent differences Category: Z L... : I oli :: fj r :/ i ~!,,_... i......,...,... i:\... ~.!..... cf. ~--~- TT l! : '\--.J i /i Temperature REF FNl ARl JPl JP AR VIZ o ::I' ~ ~-:'_:r_-.r.:~.~~- : r ool..,. -lr.u.:.,:,. :::! :. '... '.I VNi. : i i=h~ :... j; r:, L;',: : ' ::.: ::.::: : : :_ ~_\_ ~_i_t...,... ool[! i'....._;.. _i.. \...\,_... : ).... i :. : ' \ )'if!: t Hi!-.. i,...,:,.~.:~t ~.-.i r.:~~~~-~i...!'... \.. 7ooll..., n i: '.,....,,: :::. :... ' ftl ' : ''''' : ;.... I li!! ~~ I! :t~q loo OF=; ===== =====..J:,_;r-~~=-=- ===- _;_"~ j Difference of temperature ( C ) :..o ;s - REF - FNl " - ARl.,. - JPl :.: - JP "- - AR ~ - VIZ Fig..a Differences of temperature at standard pressure levels for JPl, JP, ARl, and VIZ in the night time (UTC). The reference (REF) is the average of FNl and ARL See text for details of the figures in the attached table. -9-

99 Standard deviations Category: Z Temperature REF FNl ARl JPl JP AR VIZ B B l ls Standard deviation of temperature ( oc ) ~!!! - REF Cl - FNl 'I - ARl T - JPl X - JP " - AR... - VIZ Fig..b Standard deviations of temperature differences at standard pressure levels for JP!, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. -9-

100 Consistent differences Category: Z Temperature REF FNl ARl AR AR VZ VZ FN o o o.o o o o o '. l.. '... '. -..o o..o.o j. -...o Difference of temperature ( oc ) ~ - REF - FNl 7 - ARl ~ - AR x - AR - VZ ~ - VZ m - FN Fig.l.c Same as Fig..a, for AR, AR, VZ, VZ and FN. -9-

101 Standard deviations Category: Z ~ i -, :~ ~. ~... A... lfl p Temperature REF FNl ARl AR AR VZ VZ FN r;>/j,l'~,: ; fi. 'l~:;~~~:;r... ' I ' ' ' ' [.//f' 9 9 7!!... /n..!<#:i"" '""<!' '"'" :.. IT fl I' ~ ll ~!/ 'l ~-w : oo~!fiit il Iii :... "'"'{"" ~ m:.t.. ' '""....,,!..., "<,.,, i! i \\"-,,. ~ t:: il..rp.~.. }~. '-"' ~ j!!.:;::, e ::l i, t..f'' ; (/) '"''-;;,,t.. =... (/)... p=, e il',i r ',i! =-. tl. ~. ;'} Qi'i'!\tk. <.o.....!i t'li 'I[;! ;, Jill oo~rw.: i,.! 'I'"' l, il] ;, o~ :.q;+ "':...:.... l. ( ~!I idoltj Wj,l'!.l - ~t...,... "'"".. i!t\y : 'lp i),: t} -~... ~ frill\ : h.fi'i ' i$n.. ; I',, : \ b '!'.. :.. " ' 'T.. J ~, i i!i"-.o.-'lti'.~ =... ~-.... I Lo... Standard deviation of temperature ( oc ) - REF D - FNl y - ARl T - AR : : - AR ~ - VZ "" - VZ Q - FN Fig..d Same as Fig.l.lb, for AR, AR, VZ, VZ and FN. -9-

102 Consistent differences Category: Z Temperature,:r~t ykp ['' '''''\::~ ''i"'.,.. t' : \.,'.'. I (; i: i.! l o...,....., j ~ '.; sol...,.... :\; <~.'.:_ ' )r.,.. '..,.:...., ,...,.,.' J...J.. :._j..,<').... ;... ' \f 7..;.... ' ~.<Si;.... ii ';{:\ rl i/ ooj.....,...., ~;h... t... f...., r<tj. /r.... sor...;.....,.,. u '., ' ~ Ul.: : (""'"~..., : : ~! 't I! ~ sal :...:...,.. :...L.~~-~~A... ~i. TT...,..,....,.....,.. rt'i:~"',...., ;.... ~~. ''I :.h l..,...:... '..,.. ", ooll.:...,...,...,.. ~~.\~:.. ~,.\ H..,..., i' ooc...,. : :!,IJ../i.I '... ~... t);:'.... J...,.. r.,..,. : soar...,!:... : \~.../... ~'"...,,...,...,!, ~~ I~... T.\.!.LJ... ool~... l..... ;... -,:;;r I'. /\\! I?ooli.. i...,..., İ '!"I \ lii ',! ~~ ~ \.! '( :...,... :~:.. rl.. ~.. :... /iu~ t.,.,...!.,...;...,.. J.,...;... 9['"'"l"'"i,, i.. \r rr [ : ~ ::.: r-== /\ [I i l l~!d,j,+~.. ~=-~- ~- ===+ : '"')"! ''' : I -, -.,., Difference of temperature ( oc ) REF FNl ARl JPl JP AR VIZ.o o o o !i - REF - FNl "' - ARl v - JPl :.: - JP " - AR "- - VIZ Fig..a Differences of temperature at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. -97-

103 Standard deviations Category: Z Temperature REF FNl ARl JPl JP AR VIZ...; : ' '. ' '. '.... ' '. ' '....!.. '... ( '.. '. '. '. ' '. '..7 : '''' ; :.. ;.. """"-:"... ;. """... ;.....;....;. '''''""(" '... >... ''. : '... '.. ' ,...; '("... ;.. " o ;... ;..;.. '"""!"" :..;...;...,.. ' :... ;... ; : Standard deviation of temperature ( oc ) " - REF ~ - FNl 7 - ARl " - JPl ): - JP ~ - AR "' - VIZ Fig..b Standard deviations of temperature differences at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. -9-

104 Consistent differences Category: Z Temperature REF FNl ARl AR AR VZ VZ FN li li son I j: 7ol!.. ; j: ool : : soli! i: ool i: H -~~r z..... \ > \~,I '' >... ~..... : i. _. i.i.. _-,-_.._/.... : / \ ~ :.: -~ ll !....,... < !.. ' : Difference of temperature ( oc ) !!! - REF - FNl " - ARl ' - AR :-: - AR "' - VZ "- - VZ - FN Fig..c Same as Fig..a, for AR, AR, VZ, VZ and FN. -99-

105 Standard deviations Category: Z Temperature REF FNl ARl AR AR VZ VZ FN.o.....o o h~!f i! /A l I f'y~::;~. ~+.+zy. : :.o o '., ,,,,,,, i o FNl 7 - ARl ' - AR x - AR ~ - VZ ~ - VZ ~ - FN Fig.l.d Same as Fig.l.b, for AR, AR, VZ, VZ and FN. -loo-

106 Consistent differences Category: Z Geopotential REF FNl ARl JPl JP AR VIZ ol:,, j: : I ~ : : < '===~:~~ :=-=" -~=" '~=~" i :~. ::-:;"'.~ ;.::o=,..c;~~- '--- Difference of gcopotential (m) - s - REF - - FNl 7 - ARl " - JPl x - JP " - AR ~ - VIZ Fig..a Differences of geopotential height at standard pressure levels for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. - -

107 Standard deviations Category: Z Geopotential REF FNl ARl JPl JP AR VIZ :. "" ~-:_.. _ ~ =~=~=-..::..:..=.!!--'";::.=..:.::::.-...:... ~..,;,.-=,=--=:,..::.:.~ Standard deviation of gcopotcntial (m) ~ - REF FNl 7 - ARl ' - JPl x - JP ~ - AR ~ - VIZ Fig..b Standard deviations of geopotential height differences at standard pressure levels for JPl, JP, AR and VIZ in the nighttime (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

108 Consistent differences Category: Z Geopotential REF FNl ARl AR AR VZ VZ FN,:~[lll)~ :.!... :~~I.. ~_ ~...!: '~.: \.A.! I,. : /: i: : '!,_ \'i.\.)j_ ~,i :,.,... : !,':.:':... i.. '...,,....<. '!:7 :...,: :J.r:!.. " \: \\~ i,! ;i sol' ;. ;. ;.... ;. \Of~t -+#... '... : 7ol:... :.. :...,....; H!J.lJ ' ;,! :\.I~ I \': H!,! :t,l l! oo!i -\ '... ;. HA!:$$... ;... lsoli.. :.,... :...IU.Il~.U.t..,..,..,.. : ' :., I! l'o I ~ ' zooli. :.;...,,, i l.lulll,.,...,! : Tf: -\JTif ii. : i',i illi' IJ "".!...:.... _,....., r..~.t.; ~:~;fl. _:_~~-~~,:..=_i.l._i_'~... oo ( : :. r ~.-...;...;..,. I~ ~?!, 'I!!.!.:_...,...,... oo!j... j..!...;..... '! {~.....;.., i: Jiii I' : '.!:i \!. :... :..... ~_:_... :... :' I ' " ': " ''" i. ' ' :!,h~....,..., '.",.. j,. j:"""!" '!"."! :' :'llil.. lli!i, ' '!.\l'l :,!:.:...,.;.. 7 -~.,....,... ;...,...:. '~-L....,...,..,..... :m H ' m,...:.. I'i,i.i,..,...,.;... ;... asoj!.. + :...:... ;.. i... 9sli...,...,..,. :... ~, : T.~... ;...,......,. i ' oo!'.._ --,.==... -~= "... -=;-~"""",..:..._,_..:.~".. r -o -o Difference of geopotential (m) s - REF w - FNl 7 - ARl ~ - AR x - AR ~ - VZ ~ - VZ m - FN Fig..lc Same as Fig..a, for AR, AR, VZ, VZ and FN. --

109 Standard deviations Category: Z Geopotential REF FNl ARl AR AR VZ VZ FN ll. f ii/!': ~ tl/ /: :./ - '. ' ~/ f._:-..,/-.t;..... :-. :!#/' i ~ [. "ilf'"t.: : 7~" ~ :; :-.. :, I'll ii fi oo& i! ~.. #l i ll uw ~, oo~ Ht..,....;.~!.-J.:..!.. _~_.-,:.. " lj i ;' ~ i f ~' f't" : : 7~-r-ffc"'-:- : :.... ;..,,,,,,, : : <...;.. < ~!;/]...,... ". rr : : il [ i 9srlt...!....,...!!I' I oo rr =='= Standard deviation of geopotential (m) !! - REF FNl ' - ARl V - AR X - AR ~ - VZ ~ vz "" - FN Fig..d Same as Fig..b, for AR, AR, VZ, VZ and FN. --

110 Consistent differences Category: Z Geopotential REF FNl ARl JPl JP AR VIZ ] loll ol H ol! :!: : i'" i: 'Oe' ~ e ::l "' 7:.' I' 9 9 9!: looi I r sol' I "!: : ooi! i: 7 r!: !: ooi ooi[ ooi'- - ~ - - -! E :' GooH r ool: : aol : l i: :" ; I' :. ~~=~ r Difference of geopotential (m) - REF :: - FNl V - ARl '\' - JPl :=: - JP i::.. - AR.. - VIZ Fig..a Differences of geopotential height at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. - -

111 Standard deviations Category: Z Geopotential REF FNl ARl JPl JP AR VIZ ;.. :..... i '.. '.. ;. ' '. ~ '. '..' ' '.. '... '.:......;...; :......,.,. =.. ;... :.. : ,.. \ ; :... i :.' : : <.;.. ' :".. j....: ; ~. " " :.... j.. "... ; ' ' '. ' :.. ' ' ~ ~ - REF ~ - FNl 7 - ARl ~ - JPl x - JP ~ - AR - VIZ Fig..b Standard deviations of geopotential height differences at standard pressure levels for JPl, JP, AR and VIZ in the midday (UTC). The reference (REF) is the average of FNl and ARl. See text for details of the figures in the attached table. --

112 Consistent differences Category: Z Geopotential REF FNl ARl AR AR VZ VZ FN loo I' r :! sof., [ ooi:,. I!!,. r!:'..,.! Gool i: ;.... ; Difference of geopotential (m) '" - REF - FNl " - ARl " - AR :;: - AR - - VZ " - VZ - - FN Fig.l.c Same as Fig..a, for AR, AR, VZ, VZ and FN. - 7-

113 Standard deviations Category: Z Geopotential REF FNl ARl AR AR VZ VZ FN a Standard deviation of geopotential (m) - REF FNl " - ARl ' - AR :.: - AR "' - VZ "' - VZ - - FN Fig..~ Same as Fig.l.b, for AR, AR, VZ, VZ and FN. - -

114 A R A A.g ~ A A )o At!-.a... \ I X on~n G~n.B. a.g g Gt~- fi fig Gn {;}.B.A G o rq /"-... G ~~n A X f. rv.r\j~.,. Flight No. + ARl :: AR FNl X FN o JPl A JP VIZ Fig.l. Temporal variations of tropopause heights. The points indicating the first tropopause heights and those indicating the second tropopause heights reported from FNl are linked by solid lines, respectively.

115 hpa~------~------~------~------~------~------~------~------~~ UTC \., Flight No. \ I I,.,,''..... ;::j;~ :\ :t.... ~ ~....,,/.. /A,... ~,./ -; /-... : : \ ~- ~ \~:! /...,,...,,. :! \ ~! t',. /::; ;~:- ~ /(, r;;" ARI AR FNI FN, JPI ~... ::Jr I : I ' , JP-...,---' '\ ~ \\ \ : j'i...!..."..."..:."..."..."... ~..."... :--..."... ~... ~-... ~... I~ ~~ h i I :\' i"' ~ '... : : "'''"''''''''''''':.. :... ;... ;... ~ '.. ' ~... ' '.'...;'... ' ~... '... ~. '... '.'.... ' '.. '... ". FNI FN JP! JP... ;... j.... j ''''"'':... ;... {... ; ;...;... '... ':.... '.. '... ~.... '. '..... :'... ;...;......)...; ;...;...;...: 7...,...,... ''"""'\''"'"'"'"""""""''"'''"""""'"""""''"""' '''''"'''"''''''''''''''''''' '''''''''''''''''''''!'"'"'''''''' ''''''''''''''"'''"''"'''"''"' '''"'''''''''"'"'''"'"'''"'"'''''''''''' '''''''!'''''''''''''"''''''''"'!'"'''''""''''' Fig.l. Vertical profiles of temperature from TEMP messages at UTC on February 99. The tropopause level reported from each radiosonde system is indicated by a filled circle within the profile, with the name of the system on the right side. - -

116 Appendix A Photographs of radiosondes Meisei RS- - -

117 Meisei RS-9 - -

118 Vaisala RS-N I RS-LH --

119 AIR IS-A-HS --

120 AIR IS-A-L - -

121 VIZ Markll MICROSONDE - -

122 Appendix B Location of antennas N /"">..J.J-+--Japan ( RS-) Aerological obsevatory building Surface observation field ' CJ Cl Balloon release field Hydrogen building Japan(RS-9)~ USA(IS-A-L) -7-

123 Appendix C Flight rig configuration Parachute Unwinder Balloon g I m(surface) _J_ r. -t- m.m.m I S-A-HS (USA) llarkll IIICROSONDE (USA) OR IS-A-L (USA) RS-LH (Finland) --

124 - 9-