Skip to main content

Description

SMAP Level-4 (L4) surface and root zone soil moisture (L4_SM) data are provided in three products.

The SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP, DOI: 10.5067/T5RUATAQREF8) product is a series of 3-hourly time average geophysical land surface fields that are output by the L4_SM algorithm. It is likely of primary interest to most users.

The SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU, DOI: 10.5067/02LGW4DGJYRX) product provides diagnostics from the land surface analysis updates. It consists of a series of 3-hourly instantaneous (or snapshot) files that contain the assimilated SMAP observations, the corresponding land model predictions and analysis estimates, and additional data assimilation diagnostics.

Lastly, the SMAP L4 Global 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM, DOI: 10.5067/PXQIBL2ALDZD) product provides static (time-invariant) land surface model constants that will be needed by some users for further interpretation of the geophysical land surface fields. This product consists of only one granule (file) per L4_SM data product version (as defined by a distinct Science Version ID).

For each product, SMAP L-band brightness temperature data from descending and ascending half-orbit satellite passes (approximately 6:00 a.m. and 6:00 p.m. local solar time, respectively) are assimilated into a land surface model that is gridded using an Earth-fixed, global cylindrical 9 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0) projection.

Version Description

Changes to this version include: The precipitation observations used outside of North America and the high latitudes are from Version 07 of the NASA Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement mission (IMERG) products; The L-band microwave radiative transfer model (mwRTM) was updated; The Catchment land surface model now uses climatological snow albedo values based on observations from the NASA Moderate Resolution Imaging Spectroradiometer, replacing the look-up table parameterization of earlier L4_SM versions; The assimilated brightness temperatures are now taken only from Version 6 (“R19”) of the SPL1CTB product; The brightness temperature scaling parameters in the L4_SM algorithm are now based on nine years of SMAP observations and model simulations (April 2015 – March 2024); Bug fixes. For the full major and minor version history, go to https://nsidc.org/data/smap/version-history

Product Summary

Platforms
GEOS-5 ,
SMAP
Instruments
NOT APPLICABLE ,
SMAP L-BAND RADIOMETER
Spatial Extent

N: 85.044 S: -85.044 E: 180 W: -180

Spatial Resolution
9 Kilometers x 9 Kilometers
Spatial Reference System(s)
WGS 84 / NSIDC EASE-Grid 2.0 Global (EPSG:6933)
Location
GLOBAL LAND
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2015-03-31 to Present
Concept ID
C3480441264-NSIDC_CPRD
Data State
ACTIVE
Number of Files/Granules
1
Processing Level
4
Published
Science Keywords
Soil Classification ,
Soil Depth ,
Soil Porosity ,
Soil Texture ,
Terrain Elevation

Citation

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.

Copy Citation

Reichle, R., De Lannoy, G., Koster, R., Crow, W., Kimball, J., Liu, Q., & Bechtold, M. (2025). SMAP L4 Global 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants, Version 8 [Dataset]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/PXQIBL2ALDZD Date Accessed: 2026-08-26

Documents

Publications Citing This Dataset

Filters
Title Year Author Topic
Soil moisture buffers the impact of precipitation variability on ecosystem productivity Wang, Huiqi, Bassiouni, Maoya, Kang, Yanghui, Rifai, Sami W., Gherardi, Laureano A., Ukkola, Anna, Keenan, Trevor F. Soil Classification, Soil Depth, Soil Porosity, Soil Texture, Terrain Elevation, Brightness Temperature, Surface Soil Moisture, Photosynthesis, Primary Production, Vegetation Productivity, Land Use/Land Cover Classification, Vegetation Index, Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Root Zone Soil Moisture
Streamflow calibration in ungauged basins using SWOT discharge and SMAP surface soil moisture products Crow, Wade T., Durand, Michael, Coss, Steve, Reichle, Rolf H. Soil Classification, Soil Depth, Soil Porosity, Soil Texture, Terrain Elevation
Satellite soil moisture as an additional observational constraint for machine learning-based irrigation water use modeling Huang, Xin, He, Qing, Hanasaki, Naota, Oki, Taikan Root Zone Soil Moisture, Surface Soil Moisture, Brightness Temperature, Soil Classification, Soil Depth, Soil Porosity, Soil Texture, Terrain Elevation
Spatiotemporal Seamless Estimation of Global Surface Soil Moisture Using Triple Collocation, Machine Learning, and Data Assimilation Xu, Lei, Ye, Zhenni, Dai, Jin, Li, Qi, Hong, Youting, Tao, Yun, Yu, Hongchu, Zhang, Chong, Chen, Zeqiang, Chen, Nengcheng Carbon, Nitrogen, Soil Water Holding Capacity, Soil Bulk Density, Soil Chemistry, Soil Classification, Soil Moisture/Water Content, Soil Horizons/Profile, Surface Pressure, Heat Flux, Longwave Radiation, Shortwave Radiation, Surface Temperature, Humidity, Evapotranspiration, Surface Winds, Rain, Precipitation Rate, Snow, Soil Temperature, Land Surface Temperature, Snow Water Equivalent, Runoff, Land Use/Land Cover Classification, Surface Soil Moisture, Soil Depth, Soil Porosity, Soil Texture, Terrain Elevation
You're viewing 4 of 4