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SMAP Enhanced L3 Radiometer Global and Northern Hemisphere Daily 9 km EASE-Grid Freeze/Thaw State, Version 2 (SPL3FTP_E)
Data set:
SPL3FTP_E
Citation
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.

Overview

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.
Data Contributor(s):
Xu, X., R. S. Dunbar, C. Derksen, A. Colliander, Y. Kim, and J. S. Kimball.
Parameter(s):
BRIGHTNESS TEMPERATURE FREEZE/THAW TRANSITION DIRECTION
Platform(s):
SMAP
Sensor(s):
SMAP L-BAND RADIOMETER
Data Format(s):
HDF5
Temporal Coverage:
31 March 2015 to 27 August 2020
Temporal Resolution:
1 day
Spatial Resolution:
9 km
9 km
Spatial Coverage:
N:
85.044
S:
-85.044
E:
180
W:
-180
N:
85.044
S:
45
E:
180
W:
-180

Data Access & Tools

This data set has been retired. There is a more recent version of these data.

Help Articles

How To

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. 
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.
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.
  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).
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.
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).
NASA's Global Imagery Browse Services (GIBS) provides up to date, full resolution imagery for selected NSIDC DAAC data sets. 

Getting started

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.
OPeNDAP, the Open-source Project for a Network Data Access Protocol, is a NASA community standard DAP that provides a simple way for researchers to access and work with data over the internet.
SMAP Ancillary data sets are used to produce SMAP Level-1, -2, -3, and -4 standard data products.
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.
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.