Aquarius Aquarius Validation Data System (AVDS) Aquarius satellite Arctic Gateways Arctic Ocean Arctic ocean Arctic rivers Argo Gulf of Maine Gulf of Mexico MICAP SMAP SMOS Scotian Shelf Sea Surface Salinity Water Cycle Observation Mission (WCOM) alboran sea aquarius bias characteristics brightness temperature (TB) calibration coastal combined active/passive SSS retrieval algorithm data processing different instrument configurations forward model interferometric microwave imager (IMI) mediterranean sea microwave radiometry microwave remote sensing