1 Development Of Space-borne Rain Radar In China: The First Results From Airborne Dual-Frequency Rain Radar Field Campaign Hu Yang, Honggang Yin, Jian Shang Qiong Wu, Yang Guo, Beidou Zhang National Satellite Meteorological Center July 26,2011 IGARSS’2011
Introduction of Meteorological Satellite development in china
Development status of FY3(02) dual-frequency Rain Radar
4 Orbit coverage in FY3(02) Era FY3-Am + FY3-PM + FY3-RM will consist polar orbit earth observation constellation, combined with GPM satellites, provide Globe 3-hourly high accuracy precipitation products.
5 Introduction of China Spaceborne Precipitation Radar
The main objectives of RM satellite:
Consist a Global observation constellation system with FY3-2 AM and PM satellites, as well as GPM satellite;
Improve the severe convective system monitoring ability in china together with GPM satellite;
Provide 3D precipitation structure over both ocean and land;
Improve the sensitivity and accuracy of precipitation measurement over china and arrounding area;
Instruments onboard the PR satellite platform
Core instrument : Ku/Ka Radar
MWTS ： centre frequencies set at 50.3,51.76,52.8,53.596,54.4,54.94,55.50,57.29GHz
MWHS ： centre frequencies set at 89.0,118.75±0.2, ±0.3, ±0.8, ±1.1, ±2.5, ±3.0, ±5.0,150,183.31±1, ±1.8, ±3, ±4.5, ±7
MWRI ： Centre frequencies set at 10.65,18.7,23.8,36.5,89GHz, with V/H polarization
KaPR KuPR MWRI MWTS MWHS MWRI
6 Main Instrument Characteristics KuPR KaPR Frequency 13.6 GHz 35.5 GHz Scan angle ±20º Horizontal resolution 5 km (nadir) Range resolution 250m Observation range 18 km~-5 km sensitivity 0.5 mm/h 0.2 mm/h Antenna Side lobe level -35 dB － 30dB Range side lobe -70dB -60dB accuracy ≤ ±1 dB Independent sampling number ≥ 64 Calender Year 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Ku/Ka PR Conceptual Design Preliminary Design/Airborne flight Critical Design Sustaining Design Launch Gound System Conceptual Design System Design System integeration Operation Algorithm Conceptual Design Prototype Development Development Validation
7 7 JS-RM2010 Dual-frequency Rain Radar Field Campaign Ground weather Radar Z Gnd Rain profile Z APR Inversion algorithm APR calibration Attenuation Correction Ze Rain profile Inversion algorithm Attenuation Correction Ze Radar simulator APR rain measurements simulation database TRMM-PR rain products （ 2A25 ） TRMM-PR Z PR
8 ADPR(Ku/Ka) Instrument characteristics Ku Ka Fly height 5km 5km Frequency 13.6GHz 35.5GHz Swath width 3.6km 3.6km Observation range 4km ～ -3km ASL 4km ～ -3km ASL Horizontal resolution 240m 240m Vertical resolution 250m 250m sensitivity 0.25mm/h 0.1mm/h Sample rate 64 64 Beam width 2.9 °× 2.9 ° 2.9 °× 2.9 ° Scan angle range ± 20 ° ± 20 ° Dynamical range ≥ 70dB ≥ 70dB
Dual-Frequency Radar Airborne Field Campaign (JS-RM2010) Jun-Oct, 2010 9 Ku Radar Ka Radar
Ocean surface radar backscattering characteristics 11 11 Comparing with TRMM-PR measurements over ocean surface shows that the loss of antenna radome is obvious, and the attenuation is angle dependence.
Calibration accuracy evaluation by using TRMM-PR measurements 12 12 1.Ku radar ocean sigma0 from TRMM-PR 2. Ku band ocean surface roughness parameter from TRMM-PR 3. Ku/Ka ocean surface roughness difference 4. Ka band ocean surface roughness from Ku measurments 5. Ka band ocean surface sigma0 from model ADPR Ku radar Cal/val by using TRMM-PR ADPR Ka Radar cal/val Ocean sigma0 from model computation
Antenna radiom Loss correction 13 13 The rms error of model computation is 0.78dB
Airplane-ground comparison -22- Quantitative comparison results Observation time 2010-10-11, 09:52:06~10:02:24 Matched points 4684 Maximum (dBZ) Ku ： 25.77 Ka ： 25.07 X ： 30.50 Minimum (dBZ) Ku ： -7.82 Ka ： -10.07 X ： 4.00 Mean (dBZ) Ku ： 16.38 Ka ： 14.55 X ： 19.22 RMS Ku vs. Ka ： 1.84 Ku vs. X ： 6.75 Ka vs. X ： 7.51 Correlation coefficient Ku vs. Ka ： 0.98 Ku vs. X ： 0.53 Ka vs. X ： 0.53
detection sensitivity -23- [Ku] The minimum detectable rain rate of airborne Ku-band radar is 0.15mm/h, which satisfies the desired performance of 0.25mm/h. [Ka] The minimum detectable rain rate of airborne Ka-band radar is 0.13mm/h, which is a little worse than the desired performance of 0.10mm/h. Given the rain attenuation and the radome’s influence, the sensitivity of Ka-band radar basically satisfies the desired performance.
sidelobe -24- [Ku] The sidelobe of Ku-band radar is lower than -60dB, which satisfies the desired performance. [Ka] The sidelobe of Ka-band radar is lower than -50dB, which is a little worse than the desired performance.
range resolution -25- [Ku] Actual 6dB range resolution of Ku-band radar is better than 250m, which satisfies the desired performance. [Ka] Actual 6dB range resolution of Ka-band radar is better than 250m, which satisfies the desired performance.
The radar reflectivity factor profiles of ADPR and TRMM PR are highly consistent, which proves ADPR’s measuring accuracy.
Field Campaign results shows that ADPR basically satisfy the desired performance.
The dual-frequency precipitation radar is qualified for the development of future spaceborne dual-frequency precipitation radar in China.