An ocean roughness correction algorithm for retrieving salinity on Aquarius

Aquarius/SAC-D is a joint NASA/CONAE (Argentine Space Agency) Earth Sciences satellite mission to measure the global sea surface salinity (SSS) using an L-band radiometer to measure ocean blackbody emissions also known as brightness temperature (Tb). The application of L-band radiometry to measure SSS is a difficult task, and there are many corrections that must be made correctly to obtain accurate SSS data. One of the major error sources is the effect of ocean roughness that “warms” the ocean brightness temperature (Tb). The Aquarius baseline approach uses the radar scatterometer to provide this ocean roughness correction through the correlation of radar backscatter with the excess ocean emissivity without directly measuring the surface wind speed. This paper provides an alternative approach using a theoretical Radiative Transfer Model (RTM) driven by numerical weather forecast model surface winds. The theoretical basis of our algorithm is described and results are compared with the AQ baseline scatterometer method.