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Description

This enhanced Level-3 (L3) product provides a daily composite of global and Northern Hemisphere landscape freeze/thaw conditions retrieved by the Soil Moisture Active Passive (SMAP) radiometer from 6:00 a.m. descending and 6:00 p.m. ascending half-orbit passes. This product is derived from SMAP enhanced Level-1C brightness temperatures (SPL1CTB_E). Backus-Gilbert optimal interpolation techniques are used to extract maximum information from SMAP antenna temperatures and convert them to brightness temperatures. The data are then posted to two 9 km Earth-fixed, Equal-Area Scalable Earth Grids, Version 2.0 (EASE-Grid 2.0): a global cylindrical and a Northern Hemisphere azimuthal.

Version Description

Changes to this version include: - Adjusted the freeze/thaw reference states for the normalized polarization ratio (NPR) algorithm per the improved Level-1 brightness temperature recalibration. The freezing reference averages from 2016-2020 and the thaw reference averages from 2015-2019. - Adjusted the reference states for the Single-Channel V (SCV) algorithm per the update of the GEOS-FP surface and soil temperature profiles. - Improved the never frozen/never thawed masks for false-flag mitigation by: * extending the temporal extent of the AMSR-E source data to include data through 2019 * blending in a GEOS-FP temperature climatology for 2015-2020 using a loose ±10 ºC criterion for fully-frozen or fully-thawed conditions. - The product data structure, content, and processor code are otherwise unchanged from the previous version. For the full major and minor version history, go to https://nsidc.org/data/smap/version-history

Product Summary

Platforms
SMAP
Instruments
SMAP L-BAND RADIOMETER
Spatial Extent

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

,

N: 85.044 S: 45 E: 180 W: -180

Spatial Resolution
9 Kilometers x 9 Kilometers
Spatial Reference System(s)
Multiple EPSG codes (see User Guide)
Location
GLOBAL ,
NORTHERN HEMISPHERE
Coordinate System
CARTESIAN
Granule Spatial Representation
GEODETIC
Temporal Extent
2015-03-31 to 2023-12-02
Temporal Resolution
1 Day
Concept ID
C2872771054-NSIDC_CPRD
Data State
DEPRECATED
Number of Files/Granules
0
Processing Level
3
Published
Updated
Science Keywords
Brightness Temperature ,
Freeze/Thaw ,
Transition Direction

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

Xu, X., Dunbar, R., Derksen, C., Colliander, A., Kim, Y., & Kimball, J. (2020). SMAP Enhanced L3 Radiometer Global and Northern Hemisphere Daily 9 km EASE-Grid Freeze/Thaw State, Version 3 [Dataset]. NASA National Snow and Ice Data Center Distributed Active Archive Center. https://doi.org/10.5067/ZV08T8J395JB Date Accessed: 2026-09-12

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Publications Citing This Dataset

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Title Year Author Topic
An Autoencoder Architecture for L-Band Passive Microwave Retrieval of Kumawat, Divya, Ebtehaj, Ardeshir, Xu, Xiaolan, Colliander, Andreas, Kumar, Vipin Reflectance, Total Surface Water, Transition Direction, Brightness Temperature, Freeze/Thaw, Surface Soil Moisture
Capturing constraints on boreal gross primary productivity using the Melser, Ramon, Coops, Nicholas C., Wulder, Michael A., Derksen, Chris, Knox, Sara H., Wang, Tongli Reflectance, Primary Production, Fraction Of Absorbed Photosynthetically Active Radiation (fapar), Gross Primary Production (gpp), Brightness Temperature, Freeze/Thaw, Transition Direction, Soil Organic Carbon (SOC), Root Zone Soil Moisture, Surface Soil Moisture
Characterizing satellite-derived freeze/thaw regimes through spatial and temporal clustering for the identification of growing season constraints on vegetation productivity Melser, Ramon, Coops, Nicholas C., Derksen, Chris Primary Production, Fraction Of Absorbed Photosynthetically Active Radiation (fapar), Gross Primary Production (gpp), Reflectance, Brightness Temperature, Freeze/Thaw, Transition Direction, Soil Organic Carbon (SOC)
Monitoring ECO-Hydrological Spring Onset Over Alaska and Northern Canada with Complementary Satellite Remote Sensing Data Kim, Youngwook, Kimbal, John S., Parazoo, Nicholas, Xu, Xiaolan, Dunbar, R. Scott, Colliander, Andreas, Reichle, Rolf Brightness Temperature, Freeze/Thaw, Transition Direction, Soil Organic Carbon (SOC)
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