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Description

This Level-2 (L2) soil moisture product provides estimates of land surface conditions retrieved by both the Soil Moisture Active Passive (SMAP) radiometer during 6:00 a.m. descending and 6:00 p.m. ascending half-orbit passes and the Sentinel-1A and -1B radar. SMAP L-band brightness temperatures and Copernicus Sentinel-1 C-band backscatter coefficients are used to derive soil moisture data, which are then resampled to an Earth-fixed, cylindrical 3 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0). While the 3 km data product has undergone validation, the 1 km product has not and should be used with caution.

Version Description

Changes to this version include: - An improved calibration methodology was applied to the SMAP Level-1B brightness temperatures. - Revised the coefficients in the land surface temperature computation to be consistent with the SMAP Level-2 soil moisture passive enhanced product. The new coefficients are C=0.246, K=1.007 for AM passes and C=1.0, K=1.007 for PM passes. - Changed the omega parameter of the tau-omega model for forest landcover classes (1-5) from 0.05 to 0.07. - Uses a new high-resolution soil database (SoilGrid250m; Hengl et al., 2017). - Uses bulk density to set the upper limit of the soil moisture retrievals. Previous versions used a fixed value of 0.65 m3/m3. - Enhanced documentation on Data Flags in the User Guide to help data users to better understand and use the flags. - Added a bit in the TB Disaggregation QC flag to indicate (1) the use of SMAP AM or PM data; and (2) the time difference (greater or less than 36 hours) between the SMAP and Sentinel observations overlap. - Fixed the EASE_[row/column]_index_apm_[1km/3km] data fields to make them 0-based. - Fixed the range beginning and ending time in the file metadata. For the full major and minor version history, go to https://nsidc.org/data/smap/version-history

Product Summary

Platforms
SMAP ,
Sentinel-1A ,
Sentinel-1B
Instruments
SMAP L-BAND RADIOMETER ,
C-SAR
Spatial Extent

N: 60 S: -60 E: 180 W: -180

Spatial Resolution
3 Kilometers x 3 Kilometers
Spatial Reference System(s)
WGS 84 / NSIDC EASE-Grid 2.0 Global (EPSG:6933)
Location
OCEANIA ,
AFRICA ,
ASIA ,
EUROPE ,
NORTH AMERICA ,
SOUTH AMERICA
Coordinate System
CARTESIAN
Granule Spatial Representation
GEODETIC
Temporal Extent
2015-03-31 to Present
Temporal Resolution
30 Second
Concept ID
C2938663471-NSIDC_CPRD
Data State
ACTIVE
Number of Files/Granules
1818161
Processing Level
2
Published
Updated
Science Keywords
Brightness Temperature ,
SIGMA NAUGHT ,
Surface Soil Moisture

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

Das, N., Entekhabi, D., Dunbar, R., Kim, S., Yueh, S., Colliander, A., ONeill, P., Jackson, T., Jagdhuber, T., Chen, F., Crow, W., Walker, J., Berg, A., Bosch, D., Caldwell, T., & Cosh, M. (2020). SMAP/Sentinel-1 L2 Radiometer/Radar 30-Second Scene 3 km EASE-Grid Soil Moisture, Version 3 [Data set]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/ASB0EQO2LYJV Date Accessed: 2026-05-28

Documents

Publications Citing This Dataset

Filters
Title Year Author Topic
Tocap: a web tool for ad-hoc campaign planning in terrestrial hydrology Nixdorf, Erik, Eggert, Daniel, Morstein, Peter, Kalbacher, Thomas, Dransch, Doris Brightness Temperature, SIGMA NAUGHT, Surface Soil Moisture
Evaluation of SMAP/Sentinel 1 high-resolution soil moisture data to detect irrigation over agricultural domain Jalilvand, Ehsan, Abolafia-Rosenzweig, Ronnie, Tajrishy, Masoud, Das, Narendra Vegetation Index, Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Brightness Temperature, SIGMA NAUGHT, Surface Soil Moisture, Precipitation, Precipitation Amount, Precipitation Rate, Snow, Rain
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