WindSat Polarimetric View of Greenland

Abstract

Abstract : WindSat is the first spaceborne microwave polarimetric radiometer that measures all four elements of the Stokes vector, the brightness temperatures at vertical and horizontal polarizations (TV and TH), and the real and imaginary parts of the cross-correlation of the vertical and horizontal polarization known as the third and fourth Stokes parameters (TU and TF). WindSat was developed by NRL and had been in operation since January 2003. The polarimetric signatures of the third and fourth Stokes measurements are mostly related to the asymmetric structures of the ocean-wind-driven surface roughness. Prior to the launch of WindSat, it was a common belief that land polarimetric signatures at satellite footprint scales would be below the instrument noise level and would not carry any useful geophysical information. However, postlaunch data processing reveals significant land signals in the TU and TF, particularly over Greenland and the Antarctic ice sheets, which are the most environmentally sensitive Earth media, playing a significant role in global sea level and climate changes. Understanding this polarimetric signature, uniquely afforded by WindSat, and its relation with the snow properties and microstructures will have a profound impact on climate study.