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
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.