Upper ocean salinity stratification and rain freshening in the tropics observed from Aquarius

We present validation results for the Aquarius Version 3.0 ocean surface salinity product that has been released in June 2014. We focus on comparing the Aquarius salinity in the tropics with measurements from the ARGO drifter network, moored PMEL buoys and HYCOM. The results are stratified as function of surface rain rate. As the measurements occur at different depth below the ocean surface, this allows an assessment of salinity stratification within the very upper ocean layer and rain induced freshening effects. We separate the rain freshening effects from local biases in the Aquarius salinity that correlate with sea surface temperature and are likely related to uncertainties in the geophysical model that is used in the salinity retrieval algorithm. We derive an adjustment for this SST-dependent biases and evaluate the performance of this bias-adjusted salinity product. A comparison between the standard Aquarius salinity product and the CAP salinity is also presented.