SMAP Maps: JPL CAP
This is an investigator-produced monthly mapped sea surface salinity (SSS) product from the NASA Soil Moisture Active Passive (SMAP) observatory. It is based on the Combined Active-Passive (CAP) retrieval algorithm developed at the NASA Jet Propulsion Laboratory (JPL) originally in the context of Aquarius/SAC-D and now extended to SMAP.
The maps show a range of salinities using the Practical Salinity Scale (PSS; Lewis, 1980), roughly equivalent to parts per thousand. PSS and PSU (Practical Salinity Units), are different names for the same thing.