Evaluation of WindSat ocean vector wind retrievals in tropical cyclones

WindSat is the world's first microwave polarimetric radiometer, designed to measure ocean vector winds. In late 2004, the first preliminary oceanic wind vector results were released. This paper presents an evaluation of the performance of the retrieval algorithm in hurricane conditions. Both wind speed and wind direction comparisons will be made with surface wind analysis (H*Wind) developed by the NOAA Hurricane Research Division (HRD) and provided by the NOAA National Hurricane Center (NHC). Examples are presented where HRD aircraft flights were conducted within several hours of the WindSat overpass. These H*Wind surface wind analyses provide the most complete independent surface winds comparison data set available. Both WindSat retrieved wind speeds and wind directions are evaluated (against H*Wind) as a function of storm quadrant. To determine the effects of intense rain, rain rates are retrieved with WindSat brightness temperatures using a modified version of the Goddard Profiling (GPROF) algorithm. To complement the analysis, rain rates were derived using WindSat brightness temperatures with a modified version of the TMI 2A12 heritage rain algorithm.