An introduction to atmospheric

Transcription

1 An introduction to atospheric icrowave radioetry DoeNico Ciini Institute for the Environental Analysis and Monitoring (IMAA) National Research Council of ITALY (CNR) Contributions fro: Ulrich Löhnert, Susanne Crewell, Dave Turner, Ed Westwater, Stick Ware,

2 Introduction Why MW radioetry? Very brief history Natural MW radiation What MW radioetry can provide? Advantages and liitations MWR networking MWRnet Towards operational service Suary and conclusions

3 Introduction Why icrowave radioetry? Real-tie continuous geophysical easureents Teperature profiles Huidity profiles Total colun water vapor and cloud liquid aounts Robust, all-weather, unattended instruents Passive technique: natural eission fro the atosphere

4 Introduction Very Brief History Bell Labs* First experients in 1960s NOAA (2-chan) Coercial units in late 1980s *Penzias and Wilson, Nobel Prize in Physics 1978 for discovering the cosic icrowave background radiation

5 Introduction Very Brief History 1963 at Bell Labs*, USA *Penzias and Wilson, Nobel Prize in Physics 1978 for discovering the cosic icrowave background radiation

6 Introduction Why MW radioetry? Very brief history Natural MW radiation What MW radioetry can provide? Advantages and liitations MWR networking MWRnet Towards operational service Suary and conclusions

7 Natural MW radiation MW radioeters (MWR) perfor easureent of theral radiation The observed theral radiation coes priarly fro: o Atospheric gases (oxygen and water vapor) o Hydroeteors (ainly liquid water) q The easured quantity is Radiance (R) q R is converted to Tb (brightness teperature) q Intuitive units [K] Typical spectral range GHz l ~ 1.5 c to 5

8 Natural MW radiation Theral radiation Black Body Planck s curves B[W/( 2 Hz sr)] vs. f[hz] T=6000K T=2000K T= 300K

9 Natural MW radiation Atospheric Transittance (absorption only)

10 Natural MW radiation The Atosphere is NOT a black body: Atospheric absorption coefficient in the MW O 2 H 2 O Total Water Vapor Liquid Water Oxygen

11 Natural MW radiation Diension paraeter and scattering regies x=2pr/l

12 Natural MW radiation eission eission transission absorption (( )) scattering SENSOR

13 Natural MW radiation eission eission transission absorption (( )) scattering SENSOR

14 Natural MW radiation eission eission transission absorption (( )) scattering SENSOR

15 Natural MW radiation eission eission transission absorption RFI (( )) scattering eission SENSOR

16 Atospheric MW radiative transfer T b Measured quantity = T c e Cosic background Tc ò dt = K - K -t ( 0, ) 0 + KE r) T( r) e Cosic background ter (attenuated along the path) 0 E ( dr dr Þt ( r) ò r = ò K 0 ( r) dr' Atospheric ter (eitted & attenuated along the path) Optical depth r E E ( r') dr' Atosphere Attenuation r - ò e 0 K E ( r') dr' dr Eission K E ( r) T( r) dr r Attenuation r - ò e 0 K E ( r') dr' MWR

17 What can MW radioeters provide? The Atosphere is NOT a black body: Atospheric absorption coefficient in the MW O 2 T channels Total H 2 O WV-LW channels Water Vapor Liquid Water Oxygen

18 What can MW radioeters provide? WV radioeters GHz band for WV and liquid water sensing Dual-channel integrated water vapor (IWV) and liquid water (ILW) only o IWV PWV, TCWV; ILW LWP, TCLW Multiple channels IWV, ILW, and WV profiles WV-LW channels LW WV f (GHz)

19 What can MW radioeters provide? T profiling radioeters GHz band for T sensing One channel Multiangle Usually liited to lower ~1k BL characterization Multiple channels Single- or ulti-angle Extended range (<10 k) BL characterization (if ulti-angle) T channels f (GHz)

20 What can MW radioeters provide? WV and T profiling radioeters GHz band for T, WV, and liquid water sensing Multiple channels Single- or ulti-angle Extended range (<10 k) BL characterization (if ulti-angle) T channels WV-LW channels f (GHz)

21 What can MW radioeters provide? Derived products fro T and WV profiles Virtual potential teperaure Mixing layer height (Parcel Method) Forecast indeces (e.g. K-index)

22 Advantages and liitations Advantages of MWR: Good accuracy for Tb Aziuth and elevation scanning Suitable for all weather conditions o Clear, cloudy, precipitation Continuous unattended operations at ~1in teporal resol. Ideal easureents for: o Data assiilation into NWP o Synergy with other profiling instruents (cloud radar, lidar, wind profiler)

23 Advantages and liitations Liitations of MWR: Proper calibration needs onitoring and aintenance Low-to-oderate vertical resolution o Intrinsic in passive observations o Specially true for WV and LW profiles o Higher resolution for T profiles in the BL Perforances degrade under precipitation o Retrieved products ay be not reliable o Mitigation solutions o hydrophobic coating, blowers, side-views o Perfoances depend on precipitation rate

24 Introduction Why MW radioetry? Very brief history Natural MW radiation What MW radioetry can provide? Advantages and liitations MWR networking MWRnet Towards operational service Suary and conclusions

25 MWR networking MWRnet Botto-up network grouping about 30 MWR in Europe

26 MWR networking MWRnet Ai: Addressing the lack of coordination and increase the utilization of quality controlled MWR data Goals: Establish the best practices for MWR observations and retrievals Facilitate the access of well docuented and quality controlled MWR observations and retrievals Encourage the use of MWR data for NWP and cliate applications Providing a data hub for MWR data and retrievals

27 MWR networking Towards operational service MWRnet Data assiilation experient: 13 MWR, 1-onth dataset (Oct Nov 2011) MADRID LAMPEDUSA CAGLIARI

28 MWR networking Towards operational service EUMETNET (Network of 31 EU National Meteorological Services) EUMETNET Profiling Prograe (E-PROFILE) for coordinating vertical profiles of wind, aerosols and clouds radar wind profilers Doppler wind lidars 1 st phase: autoated Lidar/Ceiloeter Proposal to EUMETNET STAC and PFAC*: Addition of MWR to E-PROFILE for profiling BL T and H Subject to approval for E-PROFILE 2 nd phase ( ) *Scientific Technical Advisory Coittee and Policy and Finance Advisory Coittee

29 Introduction Why MW radioetry? Very brief history Natural MW radiation What MW radioetry can provide? Advantages and liitations MWR networking MWRnet NWP Data Assiilation Suary and conclusions

30 Suary and Conclusions MW radioetry is a ature technique Robust, (nearly) all-weather, unattended instruents o Retrievals shall be quality-flagged (precipitation, RFI, ) Low (oderate?) aintenance o Calibration onitoring, radoe integrity Low-to-oderate vertical resolution 24/7 with ~1 in teporal resolution Suitable for network deployent Can copleent radiosonde with high teporal resolution Most of the inforation is in the atospheric boundary layer How can MWR be beneficial for operational eteorology and NWP?

31 Suary and Conclusions The planetary boundary layer (PBL) is the single ost iportant undersapled part of the atosphere* Observation gap in the PBL, particularly iportant in nowcasting and severe weather initiation 2 nd top-priority atospheric variables not currently adequately easured**: teperature and huidity profiles (in cloudy areas) *U.S. National Research Council Reports **WMO guidance on observations for NWP

32 Suary and Conclusions MWR are copleentary to Radiosondes + Better teporal resolution (diurnal cycle at ~1in) + Inforation on cloud liquid water (total colun) Moderate/low vertical resolution Satellites + Better teporal resolution (diurnal cycle at ~1in) + Higher accuracy in the PBL Low spatial coverage (representative colun) Radiosonde Satellite MWR vertical resolution spatial coverage teporal resolution Yet MWR observations are not assiilated by any NWP syste

33 References Books Atospheric Reote Sensing by Microwave Radioetry, Janssen Ed., New York, J. Wiley & Sons, Inc., Microwave Reote Sensing: Active and Passive, fro Theory to Applications, Ulaby, Moore, and Fung, Artech House, 1986 Integrated Ground-Based Observing Systes - Applications for Cliate, Meteorology, and Civil Protection, Ciini, Marzano, and Visconti, Eds., Springer, Berlin, Articles / Overview Accuracy of Boundary Layer Teperature Profiles Retrieved with Multi-frequency, Multi-angle Microwave Radioetry, Crewell and Löhnert, TGARS, 2007 Principles of Surface-based Microwave and Millieter wave Radioetric Reote Sensing of the Troposphere, Westwater, Crewell, Mäztler, and Ciini, SIEM, Surface-based Microwave and Millieter wave Radioetric Reote Sensing of the Troposphere: a Tutorial, Westwater, Crewell, Mätzler, IEEE Geosci. Re. Sens. Newslett., Guide to Microwave Weighting Function Calculations, Schroeder and Westwater, NOAA Tech. Meo. ERL WPL-225, 1992