N: 85.044 S: -85.044 E: 180 W: -180
TABLE OF CONTENTS
Description
This data set is retired and no longer available for download. We recommend using the <a href="https://nsidc.org/data/spl4smau/">newest version of SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update</a> (SPL4SMAU) data set as an alternative.
</p>
SMAP Level-4 (L4) surface and root zone soil moisture data are provided in three products:
- SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP, DOI: 10.5067/9LNYIYOBNBR5)
- SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU, DOI: 10.5067/0D8JT6S27BS9)
- SMAP L4 Global 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM, DOI: 10.5067/5C36BVQZW28K).
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 climatology to which all L4_SM precipitation forcing inputs are rescaled is now based on the climatology of the NASA IMERG-Final (Version 06B) product. Where the IMERG climatology is not available (primarily poleward of 60ºN latitude), L4_SM precipitation inputs are rescaled to the climatology of the Global Precipitation Climatology Project (GPCP) v2.3 product.
• The L4_SM precipitation forcing outside of North America and the high latitudes is now corrected to match the daily totals from the NASA IMERG (Version 06B) product. As in Version 5, precipitation corrections based on CPCU data are used in North America. The latitude band for the linear tapering of the daily precipitation corrections is now 50-60ºN/S. The IMERG-Final product, which is informed by satellite observations and monthly totals from precipitation gauges, was used during L4_SM reprocessing. Forward-processing of L4_SM uses the satellite-only IMERG-Late product, which is not informed by precipitation gauges. A change in the L4_SM Science Version ID indicates the switch from IMERG-Final to IMERG-Late inputs.
• Minor change in a parameter related to the multiplicative, lognormal perturbations of precipitation and shortwave radiation forcing to reduce minor bias between perturbed and unperturbed forcing.
The brightness temperature scaling parameters in the updated Level-4 soil moisture algorithm are based on six years of SMAP observations (April 2015 – March 2021).
Product Summary
Platforms
GEOS-5
,
Instruments
NOT APPLICABLE
,
Spatial Extent
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 2022-11-14
Temporal Resolution
3 Hour
Concept ID
C2872768133-NSIDC_CPRD
Data State
DEPRECATED
Number of Files/Granules
0
Processing Level
4
Published
Science Keywords
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
Citation Copied
Reichle, R., De Lannoy, G., Koster, R., Crow, W., Kimball, J., & Liu, Q. (2021). SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 6 [Dataset]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/6P2EV47VMYPC Date Accessed: 2026-07-29
Reichle, R., De Lannoy, G., Koster, R., Crow, W., Kimball, J., & Liu, Q. (2021). SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 6 [Dataset]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/6P2EV47VMYPC Date Accessed: 2026-07-29
Reichle, Rolf, et al. “SMAP L4 Global 3-Hourly 9 Km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 6.” NASA National Snow and Ice Data Center Distributed Active Archive Center, 2021, https://doi.org/10.5067/6P2EV47VMYPC. Date Accessed: 2026-07-29
TABLE OF CONTENTS
Documents
USER'S GUIDE
ALGORITHM THEORETICAL BASIS DOCUMENT (ATBD)
DATA PRODUCT SPECIFICATION
PRODUCT QUALITY ASSESSMENT
Publications Citing This Dataset
Filters
| Title | Year Sort ascending | Author | Topic |
|---|---|---|---|
| Assessing the influence of model inputs on performance of the EMT plus | Fischer, Samantha C., Niemann, Jeffrey D., Scalia, Joseph, Bullock, Matthew D., Proulx, Holly E., Kim, Boran, Green, Timothy R., Grazaitis, Peter J. | Heat Flux, Longwave Radiation, Shortwave Radiation, Surface Temperature, Evaporation, Evapotranspiration, Rain, Snow, Canopy Characteristics, Leaf Characteristics, Vegetation Cover, Soil Moisture/Water Content, Soil Temperature, Albedo, Land Surface Temperature, Snow Water Equivalent, Runoff, Brightness Temperature, SIGMA NAUGHT, Surface Soil Moisture | |
| Characterizing Satellite Soil Moisture Drydown: A Bivariate Filtering | Sinha, Jhilam, Sharma, Ashish, Marshall, Lucy, Kim, Seokhyeon | Vegetation Index, Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Surface Soil Moisture | |
| Current and Future Distribution of the Cataglyphis nodus (Brulle, 1833) in the Middle East and North Africa | Kalarikkal, Remya Kottarathu, Park, Hotaek, Georgiadis, Christos, Guenard, Benoit, Economo, Evan P., Kim, Youngwook | Surface Soil Moisture, Root Zone Soil Moisture | |
| Evaluation of machine learning algorithms in soil water content prediction at multiple depths | Jain, Shubham, Samanta, Sayantan, Himanshu, Sushil Kumar | Surface Soil Moisture | |
| Soil Moisture Retrieval Using in Situ and Data Simulation Regularized Deep Learning Models | Tsagkatakis, Grigorios, Moghaddam, Mahta, Tsakalides, Panagiotis | Surface Soil Moisture | |
| IMERG Precipitation Improves the SMAP Level-4 Soil Moisture Product | Reichle, Rolf H., Liu, Qing, Ardizzone, Joseph V., Crow, Wade T., De Lannoy, Gabrielle J. M., Kimball, John S., Koster, Randal D. | Surface Soil Moisture, Soil Moisture/Water Content, Soil Temperature, Precipitation, Precipitation Amount, Precipitation Rate, Snow, Rain, Brightness Temperature | |
| Satellite-based land surface temperature and soil moisture observations accurately predict soil respiration in temperate deciduous and coniferous forests | Weiland, Lelia, Rogers, Cheryl A., Sothe, Camile, Arain, M. Altaf, Gonsamo, Alemu | Land Surface Temperature, Emissivity, Surface Radiative Properties, Surface Soil Moisture | |
| Toward Improved Regional Hydrological Model Performance Using StateOfTheScience DataInformed Soil Parameters | Li, Chuxuan, Yu, Guo, Wang, Jiali, Horton, Daniel E. | Surface Pressure, Longwave Radiation, Shortwave Radiation, Surface Temperature, Evaporation, Humidity, Convection, Surface Winds, Rain, Land Surface Temperature, Heat Flux, Evapotranspiration, Snow, Canopy Characteristics, Leaf Characteristics, Vegetation Cover, Soil Moisture/Water Content, Soil Temperature, Albedo, Snow Water Equivalent, Runoff, Root Zone Soil Moisture, Surface Soil Moisture | |
| Aquifer storage change, 20182021, in the Big Chino Subbasin, Yavapai County, Arizona | Kennedy, Jeffrey R. | Surface Soil Moisture | |
| Cascading droughtheat dynamics during the 2021 Southwest United States Heatwave | Osman, M., Zaitchik, B. F., Winstead, N. S. | Leaf Area Index (LAI), Fraction Of Absorbed Photosynthetically Active Radiation (fapar), Leaf Characteristics, Photosynthetically Active Radiation, Reflectance, Albedo, Anisotropy, Surface Soil Moisture |
You're viewing 10 of 10