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Description

This Level-3 (L3) product provides a daily composite of 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. SMAP L-band brightness temperatures are used to derive freeze/thaw state and transition data, which are then resampled to both an Earth-fixed, Northern Hemisphere azimuthal 36 km Equal-Area Scalable Earth Grid (EASE-Grid 2.0), and to an Earth-fixed global 36 km EASE-Grid 2.0.

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: 45 E: 180 W: -180

,

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

Spatial Resolution
36 Kilometers x 36 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
C2872801958-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 L3 Radiometer Global and Northern Hemisphere Daily 36 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/ZJOKL452HRLD Date Accessed: 2026-06-20

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