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

2 Contents Introduction of Meteorological Satellite development in china Development status of FY3(02) dual-frequency Rain Radar Field campaign results conclusion

3 Roadmap of FenYun satellite Science Target: Global all weather, multispectral 3D detection 2006FY-2D 2007FY-3A (TEST) 2010FY-2F 2008FY-2E 2009FY-3B (TEST) 2011FY-3AM1 2012FY-3PM1 2012FY-2G 2013FY-4A (TEST) 2013FY-3RM (TEST) 2015FY-4EAST1 2014FY-3AM2 2017FY-3AM3 2015FY-3PM2 2016FY-4WEST1 2017FY-4MS (TEST) 2018FY-3PM3 2016FY-3RM1 2019FY-3RM FY-4EAST FY-4WEST FY-4MS 2008FY3A

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 Microwave sounder 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 Microwave imager 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 KuPRKaPR Frequency13.6 GHz35.5 GHz Scan angle±20º Horizontal resolution5 km (nadir) Range resolution250m Observation range18 km~-5 km sensitivity0.5 mm/h0.2 mm/h Antenna Side lobe level-35 dB － 30dB Range side lobe-70dB-60dB accuracy≤ ±1 dB Independent sampling number≥ 64 Calender Year Ku/Ka PRConceptual DesignPreliminary Design/Airborne flightCritical DesignSustaining DesignLaunch Gound SystemConceptual DesignSystem DesignSystem integerationOperation AlgorithmConceptual DesignPrototype DevelopmentDevelopmentValidation

77 Ground weather Radar Z Gnd Rain profile Z APR Inversion algorithmAPR 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 JS-RM2010 Dual-frequency Rain Radar Field Campaign

8 KuKa Fly height5km Frequency13.6GHz35.5GHz Swath width3.6km Observation range 4km ～ -3km ASL Horizontal resolution240m Vertical resolution250m sensitivity0.25mm/h0.1mm/h Sample rate64 Beam width 2.9 °× 2.9 ° Scan angle range ± 20 ° Dynamical range≥70dB ADPR(Ku/Ka) Instrument characteristics

9 Dual-Frequency Radar Airborne Field Campaign (JS-RM2010) Jun-Oct, 2010 Ku Radar Ka Radar

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11 Ocean surface radar backscattering characteristics Comparing with TRMM-PR measurements over ocean surface shows that the loss of antenna radome is obvious, and the attenuation is angle dependence.

12 Calibration accuracy evaluation by using TRMM- PR measurements 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

13 Antenna radiom Loss correction The rms error of model computation is 0.78dB

14 ADPR antenna Loss model

15 TRMM-PR Measurements over Test Area

16 ADPR Calibration Accuracy Evaluation Results Mean bias = 0.046

-17- Carborne meteorological radar: –X-band, 9.375GHz –1.5° –Volume scan –150m TRMM PR: –Ku-band, 13.6GHz –0.71° –Cross-track scan, 49 angle bins per scan –4.3km / 5km, 0.25km Satellite-Airplane-Ground Radar Zm Profile comparison Volume Scan

18 Ku band measurements Rain profile measurements comparison with TRMM-PR Ka band measurements

19 Time difference is about 40 minutes Measurements from 1.5-5Km above surface is consistent with each other, both in height and Z value; The ADPR derived Ze under 1.5Km is effected by surface return signal. ADPR rain profile Comparison with TRMM-PR

-20- Airplane-ground comparison Airplane attitude correction Processing procedures

-21- Airplane-ground comparison Vertical sections of airborne radar and ground radar Left ： airborne Ku/Ka-band precipitation radar Right ： carborne X-band meteorological radar

-22- Airplane-ground comparison Observation time , 09:52:06~10:02:24 Matched points 4684 Maximum (dBZ) Ku ： Ka ： X ： Minimum (dBZ) Ku ： Ka ： X ： 4.00 Mean (dBZ) Ku ： Ka ： X ： 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 Quantitative comparison results

-23- detection sensitivity [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.

-24- sidelobe [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.

-25- range resolution [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. 2. Field Campaign results shows that ADPR basically satisfy the desired performance. 3. The dual-frequency precipitation radar is qualified for the development of future spaceborne dual-frequency precipitation radar in China. Conclusion

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