Sea Surface Salinity Retrieval from Space: Potential Synergetic Use of GNSS-R Signals to Improve the Sea State Correction and Application to the SMOS Mission

It is accepted that the best way to retrieve sea surface salinity (SSS) is by means of L-band radiometric measurements. However, the sea surface brightness temperature (T_B) depends not only on the SSS, but also on the sea surface temperature (SST), and, more importantly, the sea state, which is usually parameterized in terms of the 10-meter height wind speed (U ₁₀) or the significant wave height (SWH). Other effects, such as the presence of foam, appear for wind speeds higher than ~7 m/s, but also depend on the sea state development, atmospheric stability, etc. Recently, it has been proposed that the mean squared slope (mss) derived from global navigation satellite signals (GNSS) reflected over the sea surface could be an appropriate sea state descriptor that could be used to make the necessary sea state T_B corrections to improve the SSS estimates. This work describes the feasibility of this technique applied to the SMOS mission of the European Space Agency and the requirements on the mss estimates to satisfy the SSS accuracy requirements