SPL4SMGP.007 SMAP L4 Global 3-hourly 9-km Surface and Root Zone Soil Moisture

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NASA/SMAP/SPL4SMGP/007
Dataset Availability
2015-03-31T12:00:00Z–2023-01-22T22:30:00
Dataset Provider
Earth Engine Snippet
ee.ImageCollection("NASA/SMAP/SPL4SMGP/007")
Tags
drought nasa smap soil-moisture surface weather

Description

The SMAP Level-4 (L4) Soil Moisture product includes surface soil moisture (0-5 cm vertical average), root-zone soil moisture (0-100 cm vertical average), and additional research products (not validated), including surface meteorological forcing variables, soil temperature, evapotranspiration, and net radiation.

SMAP L4 provides uninterrupted soil moisture data. During outages of the SMAP instrument, SMAP L4 soil moisture is based on land model simulations alone, without the concomitant assimilation of SMAP brightness temperature observations. Significant SMAP instrument outages occurred between 19 June and 23 July 2019 and between 6 August and 20 September 2022.

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.

The SPL4SMGP product includes a series of 3-hourly time-averaged geophysical data fields from the assimilation system. SPL4SMGP data are transformed to geographic coordinates using GDAL libraries before the data are ingested into Google Earth Engine.

See the SMAP L4 Soil Moisture User Guide and references therein for additional documentation and algorithm details.

Bands

Resolution
11000 meters

Bands

Name Units Min Max Description
sm_surface m^3 m^-3 0 0.9

Top layer soil moisture (0-5 cm)

sm_rootzone m^3 m^-3 0 0.9

Root zone soil moisture (0-100 cm)

sm_profile m^3 m^-3 0 0.9

Total profile soil moisture (0 cm to model bedrock depth).

sm_surface_wetness 0 1

Top layer soil wetness (0-5 cm;wetness units). Soil wetness units (dimensionless) vary between 0 and 1, indicating relative saturation between completely dry conditions and completely saturated conditions, respectively.

sm_rootzone_wetness 0 1

Root zone soil wetness (0-100 cm;wetness units). Soil wetness units (dimensionless) vary between 0 and 1, indicating relative saturation between completely dry conditions and completely saturated conditions, respectively.

sm_profile_wetness 0 1

Total profile soil wetness (0 cm to model bedrock depth; wetness units). Soil wetness units (dimensionless) vary between 0 and 1, indicating relative saturation between completely dry conditions and completely saturated conditions, respectively.

surface_temp K 180 350

Mean land surface temperature (including snow-covered land area). Excluding areas of open water and permanent ice

soil_temp_layer1 K 210 350

Soil temperature in layer 1 of soil heat diffusion model

soil_temp_layer2 K 210 330

Soil temperature in layer 2 of soil heat diffusion model

soil_temp_layer3 K 215 325

Soil temperature in layer 3 of soil heat diffusion model

soil_temp_layer4 K 220 325

Soil temperature in layer 4 of soil heat diffusion model

soil_temp_layer5 K 225 325

Soil temperature in layer 5 of soil heat diffusion model

soil_temp_layer6 K 230 320

Soil temperature in layer 6 of soil heat diffusion model

snow_mass kg m^-2 0 10000

Average snow mass (or snow water equivalent) over land fraction of grid cell

snow_depth m 0 50

Snow depth within snow-covered land fraction of grid cell

land_evapotranspiration_flux kg m^-2 s^-1 -0.001 0.001

Evapotranspiration from land

overland_runoff_flux kg m^-2 s^-1 0 0.05

Overland (surface) runoff (including throughflow)

baseflow_flux kg m^-2 s^-1 0 0.01

Baseflow

snow_melt_flux kg m^-2 s^-1 0 0.05

Snowmelt

soil_water_infiltration_flux kg m^-2 s^-1 0 0.05

Soil water infiltration rate

land_fraction_saturated 0 1

Fractional land area that is saturated and snow-free

land_fraction_unsaturated 0 1

Fractional land area that is unsaturated (but non-wilting) and snow-free

land_fraction_wilting 0 1

Fractional land area that is wilting and snow-free

land_fraction_snow_covered 0 1

Fractional land area that is snowcovered

heat_flux_sensible W m-2 -2500 3000

Sensible heat flux from land

heat_flux_latent W m-2 -2500 3000

Latent heat flux from land

heat_flux_ground W m-2 -1000 1000

Downward ground heat flux into layer 1 of soil heat diffusion model

net_downward_shortwave_flux W m-2 0 1365

Net downward shortwave flux over land

net_downward_longwave_flux W m-2 -1000 200

Net downward longwave flux over land

radiation_shortwave_downward_flux W m-2 0 1500

Downward shortwave flux incident on the surface

radiation_longwave_absorbed_flux W m-2 35 800

Absorbed (downward) longwave radiation at the surface

precipitation_total_surface_flux kg m^-2 s^-2 0 0.05

Total surface precipitation (incl. snow fall)

snowfall_surface_flux kg m^-2 s^-2 0 0.05

Surface snow fall

surface_pressure K 40000 110000

Mean land surface temperature (incl. snow-covered land area)

height_lowatmmodlay m 40 80

Center height of lowest atmospheric model layer

temp_lowatmmodlay K 180 350

Air temperature at center height of lowest atmospheric model layer

specific_humidity_lowatmmodlay kg kg^-1 0 0.4

Air specific humidity at center height of lowest atmospheric model layer

windspeed_lowatmmodlay m s^-1 -60 60

Surface wind speed at center height of lowest atmospheric model layer

vegetation_greenness_fraction 0 1

Vegetation “greenness” or fraction of transpiring leaves averaged over the land area* of the grid cell.

leaf_area_index m2 m^-2 0 10

Vegetation leaf area index

sm_rootzone_pctl percent 0 100

Root zone soil moisture (0-100 cm; percentile units)

sm_profile_pctl percent 0 100

Total profile soil moisture (0 cm to model bedrock depth; percentile units)

depth_to_water_table_from_surface_in_peat m -5 0.15

Depth to water table from mean surface elevation in peatlands (positive above ground)

free_surface_water_on_peat_flux kg m^-2 s^-1 -0.001 0.001

Change in free surface water storage on peatlands

mwrtm_vegopacity 0 2.5

Microwave radiative transfer model: Vegetation opacity.

Terms of Use

Terms of Use

This dataset is in the public domain and is available without restriction on use and distribution. See NASA's Earth Science Data & Information Policy for additional information.

Citations

Citations:
  • Reichle, R.H., G. De Lannoy, R.D. Koster, W.T. Crow, J.S. Kimball, Q. Liu, and M. Bechtold. 2022. SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 7. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi:10.5067/LWJ6TF5SZRG3

    Reichle, R.H., G. De Lannoy, R.D. Koster, W.T. Crow, J.S. Kimball, Q. Liu, and M. Bechtold. 2022. SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 7. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi:10.5067/EVKPQZ4AFC4D

    Reichle, R.H., G. De Lannoy, R.D. Koster, W.T. Crow, J.S. Kimball, Q. Liu, and M. Bechtold. 2022. SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update, Version 7. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi:10.5067/EVKPQZ4AFC4D

Explore in Earth Engine

var dataset = ee.ImageCollection('NASA/SMAP/SPL4SMGP/007')
                  .filter(ee.Filter.date('2017-04-01', '2017-04-30'));

var smSurface = dataset.select('sm_surface');
var smSurfaceVis = {
  min: 0.0,
  max: 0.9,
  palette: ['0300ff', '418504', 'efff07', 'efff07', 'ff0303'],
};
Map.setCenter(-6.746, 46.529, 2);
Map.addLayer(smSurface, smSurfaceVis, 'SM Surface');