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Performance of water vapor radiometers at 22 and 183 GHz developed at RPG

This paper discusses the performance of water vapor radiometers developed at RPG in the 22 and 183 GHz frequency bands. The instruments are capable of humidity and temperature profiling in various atmospheric conditions. The paper also includes information on instrument configurations, calibrations, and comparisons with radiosonde data.

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Performance of water vapor radiometers at 22 and 183 GHz developed at RPG

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  1. Performance of water vapor radiometers at 22 and 183 GHz developed at RPG Thomas Rose, Harald Czekala (Radiometer Physics GmbH)

  2. Microwave Bands Frequencies: Humidity Profiling: 22-31.4 GHz Band (7 channels) RPG-TEMPRO RPG-HATPRO RPG-HUMPRO Temp. Profiling (Trop.):50-59 GHz Band (7 channels) RPG-LWP 90 GHz LWP / IWV / Wet-Delay: 23.8 / 31.4 GHz 23.8 /31.4 + 90 GHz 90 / 150 GHz 183.3 GHz , 4 chan. 23.8 GHz RPG-LWP-U90 36.5/31.4 GHz

  3. HATPRO Instrument Configuration

  4. RPG-HATPRO Optical Performance temperature profiler humidity profiler 23.8 GHz, HPBW = 3.9°, Sidelobes: <-30 dB (6.5) 55.0 GHz, HPBW = 1.9°, Sidelobes: <-30 dB (4.0)

  5. HATPRO Rain / Dew Protection System • Prevent formation of • dew and rain on microwave window by: • - strong blower system • (150 Watts fan power • 1.5 kW heater module) • - Hydrophobic coating • Optional heater module • (1.5 kWatts) removable dew blower System allows for humidity profiling during fog, rain

  6. HATPRO Meteorological Station Weather Station and Time Reference: Rain Sensor: Provides rain flag for measurement documentation, control of super blower system GPS-Clock: Provides time reference standard for synchronization Humidity Sensor: Provides control of super blower system, documentation Temperature Sensor: Documentation of surface temperature Humidity Sensor Pressure Sensor: Documentation of baro-metric pressure, LN-target calibration Temp. Sensor Optional IR-Radiometer: Cloud base height detection, ceilometer function

  7. RPG-HATPRO Receiver Layout Dual Profiler Direct Detection Filterbank Receivers based on MMIC Technology:

  8. RPG Waveguide Dicke Switches

  9. RPG Waveguide Dicke Switches 90 GHz Direct Detection Receiver 150 GHz Direct Detection Receiver Dicke Switches Focussing Mirror Wire Grid

  10. RPG-HATPRO Receiver Allan Variance Receivers obey radiometer formula: or: Tested up to: tint = 1000 sec 30 sec. Integr. Time → ∆T = 0.1 K

  11. Humidity Profiler Calibrations • Automatic Calibrations: • gain calibration continuously by periodic noise injection • system noise calibration continuously by Dicke switch or • ambient target • tip curve, only for humidity profiler • Manual Calibrations: • - absolute calibration with liquid nitrogen (calibration of noise • standards)

  12. Nonlinearity Calibration System gain nonlinearity is corrected by 4 point method: Detector model: Absolute Calibration: Injection of additional noise TN from precision noise diode source 4 Equations result in: G, Tsys, TN, a

  13. Compact V-Band Receiver Design 55 dB Pre-Amplifier Splitter and Filter Section Boosters and Detectors Video Amps, MUX, 16 Bit ADC Noise Injection Coupler 70 mm 200 mm 51-59 GHz 7 Channel Filterbank Receiver Corrugated Feedhorn

  14. Compact K-Band Receiver Design 85 mm 280 mm

  15. Thermal Receiver Stabilisation Two stage thermal stabilisation system: Receiver stabilisation: <30 mK over full opera- ting temperature range (-30°C to + 45°C)

  16. 8 hours 0.1 K +40°C -30°C Thermal Receiver Stabilisation

  17. How do Retrievals Work?

  18. IWV Retrievals • 18580 high-resolution radio sondes • Rainy conditions included: RMS 0.45 kg/m^2 • Clear-sky RMS: 0.2 kg/m^2

  19. IWV Comparison with Radiosoundings HATPRO • 140 radio soundings (26. April to 4. July, Cabauw, KNMI) • Radiosonds: Vaisala RS-92 • No-Rain RMS: 0.43 kg/m^2, Bias: 0.05 kg/m^2 • Two channel RPG-LWP: RMS: 0.6 kg/m^2, Bias similar to HATPRO RS

  20. Example of Rapid WV-Fluctuations Benin, West Africa, 9. April 2006 (AMMA) changes of up to 7 kg / m^2 within 1 hour!

  21. HATPRO Humidity Profiling up to 10 km Benin, West Africa, 19. January 2006 (AMMA) 45 kg/m^2 27 kg/m^2

  22. Vertical humidity profiles (absolute humidity, 10 km)

  23. Vertical profiles (absolute humidity, 10km)

  24. HATPRO Humidity Profiling Comparison with radiosonde data. RMS Error : 1.0 g/m3 on the ground

  25. Example: Relative Humidity Profiles without T.-Profile Info 4 days time series (1740 profiles), H < 2000 m

  26. Example: Relative Humidity Profiles including T.-Profile Info 4 days time series (1740 profiles), H < 2000 m

  27. Example: Relative Humidity Profiles Temp. Inversion present Temp. Inversion present no temperature information added temperature information added

  28. LWP time series High temp. and spatial res. LWP time series for cloud analysis temp. res.: 1 sec., abs. acc.: +/-20 g/m2 ,RMS Noise: +/- 2 g/m2 30 g/m2 (=0.03 mm)

  29. Instrument Installations • University of Salford, UK • ARPAV, Weather Service of Veneto Italy • Regione Marche Civil Protection Centre / Ancona, Italy • KNMI, Dutch Weather Service, Cabauw • Tokyo University / Japan • University of Munich / Germany, Zugspitze • Meteo Swiss / Switzerland, 3 Units • AMMA Project, West Africa • Aerospace Corporation / USA • Institut für Meereskunde in Kiel / Germany, Research Ship „Polarstern“

  30. 183 GHz Water Vapour Radiometer System Performance: Frequencies: 183.3 +/- 1.4 GHz, BW: 0.8 GHz 183.3 +/- 3.6 GHz, BW: 1.0 GHz 183.3 +/- 7.0 GHz, BW: 2.0 GHz 183.3 +/- 14.0 GHz, BW: 2.0 GHz System Noise Temperatures: Channel 1: 1150 K Channel 2: 1200 K Channel 3: 1300 K Channel 4: 1250 K Sampling rate: 1 second

  31. 183 GHz WVR mounted in APEX 12 m Cassegrain Instrument operated by: MPI for Radio Astronomy in Bonn Site: Atacama desert SA (ALMA site)

  32. 183 GHz WVR Receiver Layout

  33. Summary of Important Results • IWV accuracy of 7 channel retrieval including window channel at 31.4 GHz is in the order of 0.45 kg/m^2 RMS • 2 channel radiometer (23.8 and 31.4 GHz) provides slightly less accurate IWV retrieval of 0.6 kg/m^2 RMS • IWV can be a rapidly changing parameter in particular close to the sea coast. • By including a Dicke switch to the receiver input it is possible to achieve low BT noise of 10 mK (1000 sec. integration time)

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