Ocean salinity

Ocean salinity covers sea-surface salinity and related density structure used to track freshwater fluxes, ocean circulation, stratification, and air-sea exchange. The core spaceborne measurement route is L-band microwave radiometry: SMOS, SMAP, and Aquarius-class missions retrieve salinity from brightness-temperature changes at protected L-band frequencies.^[1][2]

Operational salinity products split into direct satellite L3 fields and gap-free L4 analyses. L3 products preserve the satellite retrieval lineage, while L4 products combine SMOS, SMAP, in-situ salinity, and SST information to produce daily global sea-surface-salinity and density fields.^[3]

The practical limitations are coarse spatial resolution and corrections near land, sea ice, rain, and rough seas. Those constraints make fusion and cross-sensor harmonisation important supporting methods, but the first-choice acquisition physics remains L-band radiometry.^[1]