Data Set ID:

SMAP L3 Radiometer Global and Northern Hemisphere Daily 36 km EASE-Grid Freeze/Thaw State, Version 3

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.

This is the most recent version of these data.

Version Summary:

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

COMPREHENSIVE Level of Service

Data: Data integrity and usability verified; data customization services available for select data

Documentation: Key metadata and comprehensive user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools and data customization services

See All Level of Service Details

Data Format(s):
  • HDF5
Spatial Coverage:
N: 85.044, 
N: 85.044, 
S: 45, 
S: -85.044, 
E: 180, 
E: 180, 
W: -180
W: -180
Spatial Resolution:
  • 36 km x 36 km
Temporal Coverage:
  • 31 March 2015
Temporal Resolution1 dayMetadata XML:View Metadata Record
Data Contributor(s):Xu, X., R. S. Dunbar, C. Derksen, A. Colliander, Y. Kim, and J. S. Kimball.

Geographic Coverage

Other Access Options

Other Access Options


As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Xu, X., R. S. Dunbar, C. Derksen, A. Colliander, Y. Kim, and J. S. Kimball. 2020. SMAP L3 Radiometer Global and Northern Hemisphere Daily 36 km EASE-Grid Freeze/Thaw State, Version 3. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].

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How To

Programmatic Data Access Guide
Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system or through our Application Programming Interface (API). Our API offers you the ability to order data using specific temporal and spatial filters... read more
How do I access data using OPeNDAP?
Data can be programmatically accessed using NSIDC’s OPeNDAP Hyrax server, allowing you to reformat and subset data based on parameter and array index. For more information on OPeNDAP, including supported data sets and known issues, please see our OPeNDAP documentation: ... read more
How to learn more about SMAP ancillary data
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This step-by-step tutorial demonstrates how to access MODIS and SMAP data using the Application for Extracting and Exploring Analysis Ready Samples (AppEEARS). AppEEARS allows users to access, explore, and download point and area data with spatial, temporal, and parameter subsets. Interactive... read more
Visualize NSIDC data as WMS layers with ArcGIS and Google Earth
NASA's Global Imagery Browse Services (GIBS) provides up to date, full resolution imagery for selected NSIDC DAAC data sets. ... read more
Search, order, and customize NSIDC DAAC data with NASA Earthdata Search
NASA Earthdata Search is a map-based interface where a user can search for Earth science data, filter results based on spatial and temporal constraints, and order data with customizations including re-formatting, re-projecting, and spatial and parameter subsetting. Thousands of Earth science data... read more
Filter and order from a data set web page
Many NSIDC data set web pages provide the ability to search and filter data with spatial and temporal contstraints using a map-based interface. This article outlines how to order NSIDC DAAC data using advanced searching and filtering.  Step 1: Go to a data set web page This article will use the... read more
Visualize and download NSIDC DAAC data with NASA Worldview
NASA Worldview uses the Global Imagery Browse Service (GIBS) to provide up to date, full resolution imagery for select NSIDC DAAC data sets (see attachments below). The map interface allows users to... read more
NSIDC DAAC Data Subscription Requests
Data subscriptions are available for select NSIDC DAAC data collections (found below). Our subscription service automatically sends you new data as they are delivered from active NASA satellite missions. The service cannot be applied to past data already archived at NSIDC. This service is... read more


What are the latencies for SMAP radiometer data sets?
The following table describes both the required and actual latencies for the different SMAP radiometer data sets. Latency is defined as the time (# days, hh:mm:ss) from data acquisition to product generation. Short name Title Latency Required Actual (mean1) SPL1AP SMAP L1A... read more
What data subsetting, reformatting, and reprojection services are available for SMAP data?
The following table describes the data subsetting, reformatting, and reprojection services that are currently available for SMAP data via the NASA Earthdata Search, a Data Subscription, and... read more
How do I convert an HDF5/HDF-EOS5 file into binary format?
To convert HDF5 files into binary format you will need to use the h5dump utility, which is part of the HDF5 distribution available from the HDF Group. How you install HDF5 depends on your operating system. Full instructions for installing and using h5dump on Mac/Unix and... read more