On the correlation of area-extensive measurement of fractional area whitecap coverage with microwave brightness temperatures

On August 21, 2007, while mounted in a U.S. Navy P3 aircraft, the Naval Research Laboratorypsilas Airborne Polarimetric Microwave Imaging Radiometer (APMIR) and the University of Washingtonpsilas FoamCam recorded microwave and video images of the sea surface in the Gulf of Mexico as a function of distance from the eye of Hurricane Dean. From a working altitude of 6.1 km, the FoamCam sea surface optical imagery determined sea state, including presence of whitecaps, while APMIR measured the ocean surface brightness temperature at bands from 6.6 GHz to 37 GHz. The specific brightness temperatures measured were 6.6 VH, 6.8 VH, 7.2 VH, 10.7 V and full polarimetric data at 19.35 and 37 GHz. Collocated nearly cotemporaneous data from both SSM/I and WindSat satellite radiometer overpasses were available, as were oceanographic and meteorological data from National Buoy Data Center buoys. As an initial result from the analysis of these datasets, this paper provides a comparison of the APMIR-measured brightness temperatures with those measured by SSM/I and WindSat. The APMIR data and the surface video imagery is also used to investigate the relationship between linearly polarized microwave brightness temperatures and whitecap coverage. Future analysis directions for this data are discussed at the end of the paper.