Data Set ID: 
SPL3FTP_E

SMAP Enhanced L3 Radiometer Global and Northern Hemisphere Daily 9 km EASE-Grid Freeze/Thaw State, Version 2

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 Level-1C (L1C) interpolated brightness temperatures. 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.

There is a more recent version of these data.

Version Summary: 

Changes to this version include:

  • Implementation of a supplementary single-channel V-pol (SCV) algorithm
    for areas of lower latitudes where the seasonal difference of the NPR algorithm is
    too small to be effectively used to discriminate freeze/thaw state. This change
    provides stronger flag agreement between Tair and Tsoil, and for ascending/p.m.
    versus descending/a.m. overpasses due to physics (e.g. the NPR algorithm response to wet snow over frozen soil in spring). It also addresses an artifact of the validation approach (e.g. soils remain thawed for weeks after freeze onset in fall
    due to insulation from snow).
  • With the addition of the new SCV algorithm to augment the NPR baseline
    algorithm, spatial coverage of freeze/thaw data was extended to global. Data are
    output on a fixed global 36 km EASE-Grid 2.0 and are provided in the Freeze_Thaw_Retrieval_Data_Global group.
  • Updated retrieval_quality_flag for water contamination/permanent
    ice.
  • Implementation of false flag mitigation using TB screening and AMSR-E
    weekly climatology maps, resulting in significantly fewer false flags.

For the full major and minor version history, go to https://nsidc.org/data/smap/data_versions.

Parameter(s):
  • MICROWAVE > BRIGHTNESS TEMPERATURE
  • SNOW/ICE > FREEZE/THAW
  • SNOW/ICE > FREEZE/THAW > TRANSITION DIRECTION
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
Platform(s):SMAP
Spatial Resolution:
  • 9 km x 9 km
Sensor(s):SMAP L-BAND RADIOMETER
Temporal Coverage:
  • 31 March 2015 to 27 August 2020
Version(s):V2
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

No 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. 2018. SMAP Enhanced L3 Radiometer Global and Northern Hemisphere Daily 9 km EASE-Grid Freeze/Thaw State, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/1M7OJC7R7VKI. [Date Accessed].

It appears your Web browser is not configured to display PDF files. Download adobe Acrobat or click here to download the PDF file.

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
SMAP Ancillary data sets are used to produce SMAP Level-1, -2, -3, and -4 standard data products. Several of these ancillary data sets are produced by external organizations, such as NOAA, the NASA Global Modeling and Assimilation... 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
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
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

FAQ

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 Programmatic Access. Short name Title Subsetting Reformatting... read more
How are the enhanced SMAP radiometer products generated and what are the benefits of using these products?
There is considerable overlap of the SMAP radiometer footprints, or Instantaneous Fields of View (IFOVs), which are defined by the contours where the sensitivity of the antenna has fallen by 3db from its maximum. The IFOVs are spaced about 11 km apart in the along scan direction with scan lines... read more