Analysis of WindSat Data over Arctic Sea Ice

The radiation of the 3^rd and 4^th Stokes components emitted by Arctic sea ice and observed by the spaceborne fully polarimetric radiometer WindSat is investigated. Two types of analysis are carried out, spatial (maps of different quadrants of azimuth look angles) and temporal (time series of daily averages over small selected ranges of azimuth angles). The 3^rd Stokes component at 37 GHz has shown the highest signal during early summer (Gt2 K). The next highest signals were observed at the 10.7 GHz 3^rd and 4^th Stokes components during the summer months (Gt1 K). The 37 GHz 4^th Stokes component has shown the least variability (Lt1 K). The 10.7 GHz 4^th Stokes component has higher signal at the ice edge, confirmed from the sea ice concentration maps derived from Advanced Microwave Scanning Radiometer (AMSR-E) data, and similar to signals observed over global coastlines. From the comparison with near surface air temperature of the European Center for Medium-Range Weather Forecasts (ECMWF) model data and Scanning Multichannel Microwave/Imager (SSM/I) NASA Team ice concentrations it was concluded that the microphysical processes during early melting in the topmost sea ice layers are responsible for the high 37 GHz 3^rd Stokes signal.