Vertical variability of Sea Surface Salinity and influence on L-band brightness temperature

In preparation for SMOS Cal/Val phase, we simulate SMOS retrieved data (first cm) from in situ data (a few meters depth). We study vertical gradients of salinity in the Tropical Atlantic Ocean with three types of data: TSG and XCTD measurements from boats (POLARSTERN and ARAMIS project) and from ARGO floats. Between 0 and 10degnorth, nearly 5% of vertical gradients between 5 and 10 m are larger than 0.1 psu. They appeared in a zone characterized by warm SST and low wind and are linked to rain events or river discharges. The mean value of all the data stays less than 0.02 psu. However their distribution is skewed towards positives values, implying a non Gaussian repartition of differences between SMOS and in situ data.