Generalization of Ku-Band False-Alarm Reduction Method and Application to Cscat

Space-borne scatterometer observations are well-known ocean surface wind remote sensing instruments, they usually work at C- or Ku-band. Particularly in tropical regions, their observations are affected by rain. Rain-affected data are labeled in a quality control (QC) step during wind product generation. This is achieved by setting threshold of QC indicators. Among the applied QC indicators, a new one namely Joss proposed by Xu & Stoffelen in 2019, is characterized by a higher probability of detection (POD) of rain events. Joss particularly reduces the false alarm rate (FAR) for Ku-band observations during the rain screening as tested with reference to C-band observations., However, it is not possible in tropical regions for the Ku-band rotating fan-beam scatterometer onboard the Chinese-French Oceanographic SATellite (CFOSAT), to obtain C-band collocations with time differences less than 30 min. In our research, first, based on the results of the existing FAR reduction method, collocated C-and Ku- band observations are further investigated. Then the method is generalized, without the assistance of collocated C-band observations. Finally, application to wind product FAR reduction of CSCAT is presented. Results prove the effectiveness of the theory of this paper. Rain references are provided by products from the Global Precipitation Mission (GPM). Further research would be analysis on detailed rain effects to Ku-band scatterometers in different rain processes in tropical and sub-tropical regions to improve the established method.