“吉林一号”宽幅01B卫星GNSS-R数据风速反演研究

Wind Speed Retrieval Using GNSS-R Data from“Jilin-1”Kuanfu-01B Satellite

为了初步分析和评估“吉林一号”宽幅01B卫星全球导航卫星系统反射(global navigation satellite systemreflectometry,GNSS-R)测量数据反演海面风速的有效性和可用性,建立未标定时延多普勒相关功率峰值信噪比、归一化时延波形前沿斜率和后沿斜率反演海面风速的模型,得到了反演模型反演风速与ECMWF(European Centre for MediumRange Weather Forecasts)风速的均方根误差。当无严格数据质量控制和数据定标时,时延-多普勒图(delay-Doppler map,DDM)的峰值信噪比、时延波形前沿和后沿斜率的反演风速的均方根误差分别为3.22 m/s、3.67 m/s和3.49 m/s。当控制信噪比大于-6 dB时,DDM峰值信噪比反演的风速的均方根误差满足低风速反演精度2 m/s的需求,但数据量下降为无严格数据质量控制的78.11%;对于前沿和后沿斜率,当信噪比大于-3 dB时,均方根误差小于2 m/s,数据量下降至53.74%。结果表明“,吉林一号”宽幅01B卫星的GNSS-R数据可用于海面风速的测量。

Objectives:Spaceborne global navigation satellite system-reflectometry(GNSS-R)has been demonstrated to be effective in retrieving global sea surface wind speed,and many missions have been launched in orbit or planned.“Jilin-1”Kuanfu-01B satellite,as a commercial remote sensing satellite of China,equipped a GNSS-R instrument to observe Earths physical parameters.This paper aims to preliminarily analyze and demonstrate the effectiveness and feasibility of GNSS-R data from“Jilin-1”Kuanfu-01B satellite for retrieving sea surface wind speed.Methods:Three basic observables sensitive to wind speed,namely the delay-Doppler map(DDM)peak signal-to-noise ratio(SNR),the leading-edge slope and trailing-edge slope of the normalized delay waveform,are extracted from the DDMs of“Jilin-1”Kuanfu-01B satellite,and are used to demonstrate and assess the potential in retrieving wind speed.Three basic observables have obvious inversely proportional relationships with wind speed;therefore,an empirical exponential function is used to develop the geographic model function(GMF)between the basic observables and wind speed.Furthermore,the root mean square error(RMSE)between the retrieved wind speeds and European Centre for Medium-Range Weather Forecasts(ECMWF)data are obtained.Results:The RMSE of the retrieved wind speed using DDM peak SNR,leading-edge slope and trailingedge slope are 3.22 m/s,3.67 m/s and 3.49 m/s without data quality control and data calibration.When SNR is controlled to be larger than−6 dB,the RMSE of the retrieved wind speed using the DDM peak SNR reduces to be within 2 m/s,and the useful data are 78.11%of that without data quality control.For leading-edge slope and trailing-edge slope,when SNR threshold is−3 dB,the RMSE of retrieved wind speed is also decreased to be within 2 m/s,and the useful data reduce to 53.74%.Conclusions:The results show that the GNSS-R data from“Jilin-1”Kuanfu-01B satellite can be used to measure sea surface wind speed.The data used in the paper are uncalibrated,therefore,the retrieved performances are not optimal.It is a key work to calibrate the influence of transmitted power,transmission gain,and propagation path on the DDM.