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Full catalog/SPL4SMAU
SPL4SMAU·v008·dataset

How wet surface and root-zone soil is, from NASA's SMAP satellite and model (9 km, 3-hrly)

SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update V008
land NASA NSIDC_CPRD Level 4 active HDF5
Illustration of what How wet surface and root-zone soil is, from NASA's SMAP satellite and model (9 km, 3-hrly) shows
Illustration of the concept — not real satellite data.
In plain English

What it measures. How wet the soil is, both at the surface and in the root zone (the deeper layer plants draw from), as a model-corrected estimate on a 9 km grid every 3 hours. This particular file also shows the corrections made and diagnostic details.

How it's made. Produced by SMAP's Level-4 system, which feeds the satellite's microwave brightness-temperature readings into a land-surface model (GEOS-5) to estimate moisture deeper than the satellite can directly see.

How & where you'd use it. Useful for agriculture, drought and flood assessment, and weather and climate models that need root-zone soil moisture. This 'analysis update' file is mainly for users wanting to inspect how the assimilation adjusted the model, rather than the main geophysical product.

What's measured

LAND SURFACE › SOILS › SOIL MOISTURE/WATER CONTENT › ROOT ZONE SOIL MOISTURELAND SURFACE › SOILS › SOIL MOISTURE/WATER CONTENT › SURFACE SOIL MOISTURE

Coverage & cadence

  • Time span2015-03-31 → ongoing
  • Measured byGEOS-5 (NOT APPLICABLE) · SMAP (SMAP L-BAND RADIOMETER)
  • Processing levelLevel 4
  • Spatial extent-180, -85.044, 180, 85.044
  • FormatsHDF5
  • StatusACTIVE

What you can do with it

  • Track deforestation, fire scars and land-cover change
  • Monitor crop and vegetation health (NDVI/EVI)
  • Map how built-up vs. green an area is over time
Official description

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.

Get the data

spl4smau_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="SPL4SMAU",
    version="008",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from NSIDC_CPRD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.