SMAP L4 Global 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants, Version 8
Data set id:
SPL4SMLM
DOI: 10.5067/PXQIBL2ALDZD
This is the most recent version of these data.
Version Summary
Version Summary
Changes to this version include:
- The precipitation observations used outside of North America and the high latitudes are from Version 07 of the NASA Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement mission (IMERG) products. Precipitation rates from the IMERG-Final half-hourly product for a given month are used only where they are consistent with the rates of the IMERG-Final monthly product. In this case, the (hourly) L4_SM precipitation forcing is corrected to match the IMERG-Final daily total precipitation. When the IMERG-Final half-hourly data are inconsistent with the corresponding IMERG-Final monthly data, which is typically the case for solid precipitation (snowfall), the L4_SM precipitation forcing is corrected to match only the IMERG-Final monthly total precipitation.
- The L-band microwave radiative transfer model (mwRTM) was updated as follows: the mwRTM uses the Mironov soil mixing approach, replacing the Wang & Schmugge model used in earlier L4_SM versions; the mwRTM uses updated values of the L-band scattering albedo, soil roughness, and vegetation opacity climatology obtained from Version 6 of the SMAP Level-2 dual-channel soil moisture retrieval product (SPL2SMP_E); the mwRTM uses updated values of the polarization mixing parameters of the rough surface reflectivity, matching those of the SPL2SMP_E product.
- The Catchment land surface model now uses climatological snow albedo values based on observations from the NASA Moderate Resolution Imaging Spectroradiometer, replacing the look-up table parameterization of earlier L4_SM versions.
- The assimilated brightness temperatures are now taken only from Version 6 (“R19”) of the SPL1CTB product.
- The brightness temperature scaling parameters in the L4_SM algorithm are now based on nine years of SMAP observations and model simulations (April 2015 – March 2024).
- Two bug fixes were implemented. The first corrects excessive precipitation rates that occasionally appeared along certain longitudes in North America in earlier versions of L4_SM. The second fixes an error in the ancillary soil data that misclassified a small region in Argentina as peat.
For the full major and minor version history, go to https://nsidc.org/data/smap/version-history
- The precipitation observations used outside of North America and the high latitudes are from Version 07 of the NASA Integrated Multi-satellitE Retrievals for the Global Precipitation Measurement mission (IMERG) products. Precipitation rates from the IMERG-Final half-hourly product for a given month are used only where they are consistent with the rates of the IMERG-Final monthly product. In this case, the (hourly) L4_SM precipitation forcing is corrected to match the IMERG-Final daily total precipitation. When the IMERG-Final half-hourly data are inconsistent with the corresponding IMERG-Final monthly data, which is typically the case for solid precipitation (snowfall), the L4_SM precipitation forcing is corrected to match only the IMERG-Final monthly total precipitation.
- The L-band microwave radiative transfer model (mwRTM) was updated as follows: the mwRTM uses the Mironov soil mixing approach, replacing the Wang & Schmugge model used in earlier L4_SM versions; the mwRTM uses updated values of the L-band scattering albedo, soil roughness, and vegetation opacity climatology obtained from Version 6 of the SMAP Level-2 dual-channel soil moisture retrieval product (SPL2SMP_E); the mwRTM uses updated values of the polarization mixing parameters of the rough surface reflectivity, matching those of the SPL2SMP_E product.
- The Catchment land surface model now uses climatological snow albedo values based on observations from the NASA Moderate Resolution Imaging Spectroradiometer, replacing the look-up table parameterization of earlier L4_SM versions.
- The assimilated brightness temperatures are now taken only from Version 6 (“R19”) of the SPL1CTB product.
- The brightness temperature scaling parameters in the L4_SM algorithm are now based on nine years of SMAP observations and model simulations (April 2015 – March 2024).
- Two bug fixes were implemented. The first corrects excessive precipitation rates that occasionally appeared along certain longitudes in North America in earlier versions of L4_SM. The second fixes an error in the ancillary soil data that misclassified a small region in Argentina as peat.
For the full major and minor version history, go to https://nsidc.org/data/smap/version-history
Overview
SMAP Level-4 (L4) surface and root zone soil moisture (L4_SM) data are provided in three products.
The SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP, DOI: 10.5067/T5RUATAQREF8) product is a series of 3-hourly time average geophysical land surface fields that are output by the L4_SM algorithm. It is likely of primary interest to most users.
The SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU, DOI: 10.5067/02LGW4DGJYRX) product provides diagnostics from the land surface analysis updates. It consists of a series of 3-hourly instantaneous (or snapshot) files that contain the assimilated SMAP observations, the corresponding land model predictions and analysis estimates, and additional data assimilation diagnostics.
Lastly, the SMAP L4 Global 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM, DOI: 10.5067/PXQIBL2ALDZD) product provides static (time-invariant) land surface model constants that will be needed by some users for further interpretation of the geophysical land surface fields. This product consists of only one granule (file) per L4_SM data product version (as defined by a distinct Science Version ID).
For each product, SMAP L-band brightness temperature data from descending and ascending half-orbit satellite passes (approximately 6:00 a.m. and 6:00 p.m. local solar time, respectively) are assimilated into a land surface model that is gridded using an Earth-fixed, global cylindrical 9 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0) projection.
Parameter(s):
SOIL CLASSIFICATIONSOIL DEPTHSOIL POROSITYSOIL TEXTURETERRAIN ELEVATION
Platform(s):
GEOS-5, SMAP
Sensor(s):
NOT APPLICABLE, SMAP L-BAND RADIOMETER
Data Format(s):
HDF5
Temporal Coverage:
31 March 2015 to present
Temporal Resolution:
- Not applicable
Spatial Resolution:
- 9 km
- 9 km
Spatial Reference System(s):
WGS 84 / NSIDC EASE-Grid 2.0 Global
EPSG:6933
Spatial Coverage:
N:
85.044
S:
-85.044
E:
180
W:
-180
Blue outlined yellow areas on the map below indicate the spatial coverage for this data set.
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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.
This short article describes the customization services available for SMAP data using Earthdata Search.
There are a few reasons that the soil moisture data values in SMAP Level-4 data products may vary from what you expect in a particular region. The first step a data user should take in investigating apparently anomalous values is to look at the rich quality information and other data flags c
The surface and root zone soil moisture estimates in the SMAP Level-4 soil moisture products are the outputs of a land surface model into which SMAP observations of brightness temperature have been assimilated.
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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.
The following are instructions on how to import and geolocate SMAP Level-3 Radiometer Soil Moisture HDF5 data in ENVI.
Testing notes
Software: ENVI
Software version: 5.3
Platform: Windows 7
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