A new semi-empirical sea surface microwave backscatter model coupled with the rain effect

The geophysical model function is generally employed to invert the surface wind speed using scatterometer or synthetic aperture radar (SAR) measurements over the ocean. The GMF relates the normalized radar cross-section (NRCS) to the incidence angle and wind vector. The rain effect on NRCS is not considered in the GMF. In raining areas, the NRCS of the ocean surface is altered by rain. Rain contamination introduces errors to wind speed retrieved by scatterometer, particularly at high incidence angles [1]. Moreover, under extreme weather conditions, significant differences exist between the SAR retrieved wind speed and those measured by Stepped-Frequency Microwave Radiometer (SFMR) measurements in hurricane eyewall regions [2], due to the intense rainfall there. The challenges in satellite retrievals of ocean winds related to precipitation effects has been elaborated in [3].