The NASA SMAP satellite mission has provided global L-band radiometry measurements since early 2015. The instrument features advanced radio-frequency interference (RFI) detection and mitigation capabilities.  The globe can be mapped with 2 to 3 days.  Over land, the measurements are used to infer surface soil moisture fields and above-ground vegetation water content, which are key variables for watershed modeling, agricultural monitoring, and flood prediction. Over the oceans and coastal zones, the measurements can be used to infer sea surface salinity dynamical features due to riverine freshwater runoff and coastal mixing. Over land ice-covered regions, the liquid content of ice can be quantified.  Such collection of observations allow new and holistic insights the Earth system’s terrestrial and coastal water cycles. They also have use-cases (e.g., in monitoring, modeling, analysis, prediction, and disaster response) beneficial to society. This session presents science and application topics based on the long-term SMAP L-band radiometry.