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Description
This enhanced Level-3 (L3) soil moisture product provides a composite of daily estimates of global land surface conditions retrieved by the Soil Moisture Active Passive (SMAP) radiometer. This product is a daily composite of SMAP Level-2 (L2) soil moisture which is derived from SMAP Level-1C (L1C) interpolated brightness temperatures. Backus-Gilbert optimal interpolation techniques are used to extract information from SMAP antenna temperatures and convert them to brightness temperatures, which are posted to the 9 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0) in a global cylindrical projection. As of 2021, the data are also posted to the Northern Hemisphere EASE-Grid 2.0, an azimuthal equal-area projection.
Version Description
Changes to this version include:
- Dual Channel Algorithm (DCA) replaces Single Channel Algorithm – Vertical (SCA-V) as the baseline algorithm
- Addition of AM and PM north-polar grid soil moisture retrievals. This update is intended to mitigate the distortion of global-grid cells at high northern latitudes (> 50N).
- Bulk_density maximum value changed from 1.0 to 2.65.
Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.
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ONeill, P., Chan, S., Njoku, E., Jackson, T., Bindlish, R., Chaubell, J., & Colliander, A. (2021). SMAP Enhanced L3 Radiometer Global and Polar Grid Daily 9 km EASE-Grid Soil Moisture, Version 5 [Data set]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/4DQ54OUIJ9DL Date Accessed: 2026-06-17
ONeill, Peggy, Steven Chan, Eni Njoku, Thomas Jackson, Rajat Bindlish, Julian Chaubell, and Andreas Colliander. “SMAP Enhanced L3 Radiometer Global and Polar Grid Daily 9 Km EASE-Grid Soil Moisture, Version 5.” NASA National Snow and Ice Data Center Distributed Active Archive Center, 2021. doi:10.5067/4DQ54OUIJ9DL. Date Accessed: 2026-06-17
ONeill, Peggy, et al. SMAP Enhanced L3 Radiometer Global and Polar Grid Daily 9 Km EASE-Grid Soil Moisture, Version 5. NASA National Snow and Ice Data Center Distributed Active Archive Center, 2021, doi:10.5067/4DQ54OUIJ9DL. Date Accessed: 2026-06-17
Huang, Min, Carmichael, Gregory R., Bowman, Kevin W., De Smedt, Isabelle, Colliander, Andreas, Cosh, Michael H., Kumar, Sujay V., Guenther, Alex B., Janz, Scott J., Stauffer, Ryan M., Thompson, Anne M., Fedkin, Niko M., Swap, Robert J., Bolten, John D., Joseph, Alicia T.