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Description

SMAP Level-4 (L4) surface and root zone soil moisture data are provided in three products: (1) SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP). (2) SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU). (3) SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM).

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: (1) SMAP observations are now assimilated in Eastern Europe, the Middle East, and East Asia due to expanded coverage of the brightness temperature scaling parameters. The latter are based on two years of SMAP Version 3 brightness temperature observations where the SMOS climatology is unavailable due to RFI. (2) An improved version of the model-only Nature Run (NRv4.1) simulation is used to derive the brightness temperature scaling parameters, the model soil moisture initial conditions, and the soil moisture climatology. (3) Minor bug fixes.

Product Summary

Platforms
SMAP
Instruments
SMAP L-BAND RADAR
Spatial Extent

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

Spatial Resolution
9 Kilometers x 9 Kilometers
Location
GLOBAL LAND
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2015-03-31 to 2018-06-05
Temporal Resolution
3 Hour
Concept ID
C4114261210-NSIDC_CPRD
Data State
DEPRECATED
Number of Files/Granules
0
Processing Level
4
Published
Science Keywords
Root Zone Soil Moisture ,
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

Reichle, R., De Lannoy, G., Koster, R., Crow, W., & Kimball, J. (2017). SMAP L4 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 3 [Data set]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/20ULJH6EZKFJ Date Accessed: 2026-05-26

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