National Aeronautics and Space Administration

The NASA Soil Moisture Active and Passive (SMAP) satellite mission provides L-band (1.4 GHz) passive microwave brightness temperature observations that are sensitive to surface (0-5 cm) soil moisture and temperature. Several of the key applications targeted by SMAP, however, require knowledge of deeper-layer, "root zone" (0-100 cm) soil moisture and land surface carbon fluxes, which are not directly measured by SMAP. GMAO, in collaboration with The University of Montana and the NASA Jet Propulsion Laboratory, contributes to SMAP by providing value-added Level-4 data products.

The Level-4 datasets rely on the merger of SMAP observations into physically-based numerical models of the land surface water, energy, and carbon cycles. Available Level-4 data include global, 9-km, 3-hourly estimates of surface and root zone soil moisture, surface and soil temperature, and land surface fluxes, along with algorithm diagnostics from the ensemble-based data assimilation system. Level-4 data further include global, 9-km, daily estimates of net ecosystem CO₂ exchange, component carbon stocks and fluxes, and sub-grid information broken down by plant functional types.