Evaluation of the Atmospheric Upward Thermal Emission Towards SSS Retrieval at L Band

In the framework of actual and future L-band satellite radiometric missions devoted to ocean observation, and in particular to the retrieval of sea surface salinity, it is important to accurately evaluate every single contribution to the signal that can affect the retrieval algorithm. This paper presents the results of the comparison between the atmospheric contribution to the signal, as computed by the SMOS Surface Sea Salinity (SSS) algorithm, and that predicted by a multi-layer forward model driven by radio sounding data. This preliminary analysis focuses on two years of radiosonde measurements collected in a specific test site (Kauai Island, HI, USA) to estimate the Top of Atmosphere (TOA) brightness temperature TB under well-controlled conditions. As expected, while the two predicted sets of TB are statistically in good agreement, differences occur under high humidity hot weather conditions. In these cases, the difference between the two methods exceeds 0.2 K and 0.5 K at V and H polarization, respectively. Such fluctuations have an impact on SSS estimate