Sea surface salinity roughness correction at L-band for Aquarius instrument

Aquarius/SAC-D is a joint NASA/CONAE (Argentine Space Agency) Earth Science satellite mission to measure the global sea surface salinity (SSS). The prime remote sensor is an L-band microwave radiometer to measure ocean blackbody emission (brightness temperature, Tb), which depends upon the sea surface temperature and SSS. The application of L-band radiometry to measure SSS is a difficult task, and there are many Tb 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 Tb. The Aquarius baseline approach uses the coincident 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 for ocean surface wind vector. The theoretical basis of our algorithm is described and results are compared with the AQ baseline scatterometer method.