Salinity is generally defined as the concentration of dissolved salt in a parcel of seawater. Sea Surface Salinity, as measured on the Bulk Meteorology Instrument Packages, specifically refers to the Practical Salinity at the sea surface. Practical Salinity is a unitless quantity calculated from the conductivity of seawater and adjusted for temperature and pressure. It is approximately equivalent to Absolute Salinity (the mass fraction of dissolved salt in seawater) but they are not interchangeable.
The following instrument classes include this data product: