Below are land correction validation graphs based on
HYCOM. Improvement in sea surface salinity (SSS) retrieval accuracy as a function of land fraction and distance from coast. LEFT: Land fraction corresponds to the magnitude of the land signal into the antenna. We see a very significant improvement in the bias and RMS of the retrieved salinity as compared to HYCOM. RIGHT: The odd-looking reversal in trend versus distance to coast can be due to very small islands which can be close but not have significant land contamination.
(Source: SMAP JPL Version 5 User's Guide)