Influence of sea surface emissivity model parameters at L-band for the estimation of salinity

Abstract

In order to prepare the Soil Moisture and Ocean Salinity (SMOS) mission, we present sensitivity studies on a two-scale sea surface emissivity model used to compute brightness temperatures ( T B ) from the Sea Surface Temperature (SST), the wind vector, the incidence angle and the Sea Surface Salinity (SSS). We analyse the impact of uncertainties of the model on T B at 1.4 GHz ( u 0 = 21 cm), namely we determine the influence of the parametrization of the sea surface permittivity and of the cutoff wavelength u d (the limit which separates the short scales of the wave spectrum from the large scales). Using two existing permittivity parametrizations we find differences on T B ranging from 0.4 to 1.1 K. For SST warmer than 12°C and incidence angles smaller than 35°, the difference on T B is a bias independent of SSS and weakly dependent on SST. For these small incidence angles, the choice of the cutoff wavelength does not lead to significant differences on T B . For incidence angles larger than 40°, the permittivity parametrization and the choice of u d are more critical, resulting in a variation of T B of several tenths of a Kelvin.