The Soil Moisture Operational Products System (SMOPS) combines soil moisture retrievals from multi-satellites/sensors to provide a global soil moisture map with more spatial and temporal coverage. More recently, the SMOPS has been updated to retrieve soil moisture with near-real time SMAP data and also include the soil moisture retrievals from SMAP and GMI, which is on board GPM. The SMOPS now provides a seamless soil moisture map over global land from five satellites, including GPM, SMAP, GCOM-W1, and MetOp-B.
The global soil moisture maps are generated in 6-hourly and daily intervals with the latest 6 and 24 hours worth of soil moisture retrievals from multi-satellites/algorithms, and mapped with a cylindrical projection on 0.25 x 0.25 degree grids. For each grid point of the map, the output includes soil moisture values (%vol/vol) of the surface (top 1-5 cm) soil layer with associated quality information and metadata. The 6-hourly product is available in GRIB2 format at standard forecast times (00Z, 06Z, 12Z and 18Z), and the daily product is available in both GRIB2 and netCDF4 formats.
Details on the algorithm can be found at Algorithm Description