A renewal of interest for the radiometric L-band (21 cm) sea surface salinity (SSS) remote sensing appeared in the 1990s and led to the launch of the space missions SMOS (November 2009) and Aquarius (June 2011). However, due to the low signal to noise ratio, retrieving SSS from L-band radiometry is very challenging. This work focuses on the study of the L-band radiometric signature of the ocean surface properties (especially SSS and roughness), using measurements from the CAROLS airborne L-band radiometer. These measurements were acquired in the Bay of Biscay in 2009 and 2010. A first study shows that SSS derived from CAROLS radiometer measurements was accurate to better than 0.3 pss in an area of high spatial and temporal variability with a higher accuracy than coastal numerical models. The second study which combines passive (CAROLS) and active (C-band scatterometer STORM) measurements, shows the improvement of the new satellite roughness models compared to pre-launch models. In addition, the study shows the importance of taking into account the medium and large roughness scales (> 20 cm) for the interpretation of radiometric measurements far from the nadir.
