Effect of long waves on Ku-band ocean radar backscatter at low incidence angles using TRMM and altimeter data

This letter uses a large ocean satellite data set to document relationships between Ku-band radar backscatter (sigma-0) of the sea surface, near-surface wind speed (U), and ocean wave height (SWH). The observations come from satellite crossovers of the Tropical Rainfall Mapping Mission (TRMM) Precipitation Radar (PR) and two satellite altimeters, namely: 1) Jason-1 and 2) ENVISAT. At these nodes, we obtain TRMM clear-air normalized radar cross-section data along with coincident altimeter-derived significant wave height. Wind speed estimates come from the European Centre for Medium-Range Weather Forecast. TRMM PR is the first satellite to measure low incidence Ku-band ocean backscatter at a continuum of incidence angles from 0 degrees to 18 degrees. This letter utilizes these global ocean data to assess hypotheses developed in past theoretical and field studies.