Data Fields - SMAP L4 Global 3-hourly 9 km Surface and Rootzone Soil Moisture, Version 3

This page provides a description of all data fields within the SMAP L4 Global 3-hourly 9 km Surface and Rootzone Soil Moisture product. The data are grouped into the following main HDF5 groups : 

For a description of metadata fields for this product, refer to the Metadata Fields document.

* As reflected in the file names, gph, aup, and lmc indicate three different file collections: geophysical, analysis, and land-model-constants data, respectively. Note that analysis, forecast, and observations data are contained in the aup collection.

Geophysical_Data

Table 1 describes the data fields in the Geophysical_Data group stored in the gph file collection. This group contains fields that specify time-average geophysical data (including soil moisture, soil temperature, and land surface fluxes). Time and space coordinate information is stored in the HDF5 root data group.

Table 1. Data Fields for Geophysical_Data
Data Field Name Type Shape Unit Valid Min Valid Max Fill Value
baseflow_flux Float32 LatCell_LonCell_Array kg m-2 s-1 0.0 0.01 -9999.0
heat_flux_ground Float32 LatCell_LonCell_Array W m-2 -1000.0 1000.0 -9999.0
heat_flux_latent Float32 LatCell_LonCell_Array W m-2 -2500.0 3000.0 -9999.0
heat_flux_sensible Float32 LatCell_LonCell_Array W m-2 -2500.0 3000.0 -9999.0
height_lowatmmodlay Float32 LatCell_LonCell_Array m 40.0 80.0 -9999.0
land_evapotranspiration_flux Float32 LatCell_LonCell_Array kg m-2 s-1 -0.001 0.001 -9999.0
land_fraction_saturated Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
land_fraction_snow_covered Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
land_fraction_unsaturated Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
land_fraction_wilting Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
leaf_area_index Float32 LatCell_LonCell_Array m2 m-2 0.0 10.0 -9999.0
net_downward_longwave_flux Float32 LatCell_LonCell_Array W m-2 -1000.0 200.0 -9999.0
net_downward_shortwave_flux Float32 LatCell_LonCell_Array W m-2 0.0 1365.0 -9999.0
overland_runoff_flux Float32 LatCell_LonCell_Array kg m-2 s-1 0.0 0.05 -9999.0
precipitation_total_surface_flux Float32 LatCell_LonCell_Array kg m-2 s-1 0.0 0.05 -9999.0
radiation_longwave_absorbed_flux Float32 LatCell_LonCell_Array W m-2 35.0 800.0 -9999.0
radiation_shortwave_downward_flux Float32 LatCell_LonCell_Array W m-2 0.0 1500.0 -9999.0
sm_profile Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_profile_pctl Float32 LatCell_LonCell_Array percent 0.0 100.0 -9999.0
sm_profile_wetness Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
sm_rootzone Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_rootzone_pctl Float32 LatCell_LonCell_Array percent 0.0 100.0 -9999.0
sm_rootzone_wetness Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
sm_surface Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_surface_wetness Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
snow_depth Float32 LatCell_LonCell_Array m 0.0 50.0 -9999.0
snow_mass Float32 LatCell_LonCell_Array kg m-2 0.0 10000.0 -9999.0
snow_melt_flux Float32 LatCell_LonCell_Array kg m-2 s-1 0.0 0.05 -9999.0
snowfall_surface_flux Float32 LatCell_LonCell_Array kg m-2 s-1 0.0 0.05 -9999.0
soil_temp_layer1 Float32 LatCell_LonCell_Array K 210.0 340.0 -9999.0
soil_temp_layer2 Float32 LatCell_LonCell_Array K 210.0 330.0 -9999.0
soil_temp_layer3 Float32 LatCell_LonCell_Array K 215.0 325.0 -9999.0
soil_temp_layer4 Float32 LatCell_LonCell_Array K 220.0 325.0 -9999.0
soil_temp_layer5 Float32 LatCell_LonCell_Array K 225.0 325.0 -9999.0
soil_temp_layer6 Float32 LatCell_LonCell_Array K 230.0 320.0 -9999.0
soil_water_infiltration_flux Float32 LatCell_LonCell_Array kg m-2 s-1 0.0 0.05 -9999.0
specific_humidity_lowatmmodlay Float32 LatCell_LonCell_Array kg kg-1 0.0 0.4 -9999.0
surface_pressure Float32 LatCell_LonCell_Array Pa 40000.0 110000.0 -9999.0
surface_temp Float32 LatCell_LonCell_Array K 180.0 350.0 -9999.0
temp_lowatmmodlay Float32 LatCell_LonCell_Array K 180.0 350.0 -9999.0
vegetation_greenness_fraction Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
windspeed_ lowatmmodlay Float32 LatCell_LonCell_Array m s-1 -60.0 60.0 -9999.0
cell_column1 Unsigned32 LatCell_LonCell_Array dimensionless 0 3855 4294967294
cell_lat1 Float32 LatCell_LonCell_Array degrees -90.0 90.0 -9999.0
cell_lon1 Float32 LatCell_LonCell_Array degrees -180.0 180.0 -9999.0
cell_row1 Unsigned32 LatCell_LonCell_Array dimensionless 0 1623 4294967294
time 1 Float64 LatCell_LonCell_Array seconds since 2000-01-01 11:58:55.816 N/A N/A N/A

Analysis_Data [top]

Table 2 describes the data fields in the Analysis_Data group stored in the aup file collection. This group contains soil moisture and temperature estimates after the ensemble Kalman filter analysis update, along with their corresponding uncertainty estimates. Soil moisture and temperature values are snapshots/instantaneous data. Time and space coordinate information is stored in the HDF5 root data group.

Table 2. Data Fields for Analysis_Data group
Data Field Name Type Shape Unit Valid Min Valid Max Fill Value
sm_profile_analysis Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_profile_analysis_ensstd Float32 LatCell_LonCell_Array m3 m-3 0.0 1.0 -9999.0
sm_rootzone_analysis Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_rootzone_analysis_ensstd Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_surface_analysis Float32 LatCell_LonCell_Array m3 m-3 0.0 1.0 -9999.0
sm_surface_analysis_ensstd Float32 LatCell_LonCell_Array m3 m-3 0.0 1.0 -9999.0
soil_temp_layer1_analysis Float32 LatCell_LonCell_Array K 210.0 340.0 -9999.0
soil_temp_layer1_analysis_ensstd Float32 LatCell_LonCell_Array K 0.0 50.0 -9999.0
surface_temp_analysis Float32 LatCell_LonCell_Array K 180.0 350.0 -9999.0
surface_temp_analysis_ensstd Float32 LatCell_LonCell_Array K 0.0 50.0 -9999.0
cell_column1 Unsigned32 LatCell_LonCell_Array dimensionless 0 3855 4294967294
cell_lat1 Float32 LatCell_LonCell_Array degrees -90.0 90.0 -9999.0
cell_lon1 Float32 LatCell_LonCell_Array degrees -180.0 180.0 -9999.0
cell_row1 Unsigned32 LatCell_LonCell_Array dimensionless 0 1623 4294967294
time1 Float64 LatCell_LonCell_Array seconds since 2000-01-01 11:58:55.816 N/A N/A N/A

Forecast_Data [top]

Table 3 describes the data fields in the Forecast_Data group stored in the aup file collection. This group is the land model equivalent of the Observations_Data group; it provides the land surface model’s predictions of the assimilated observations. These forecasts, or observation predictions, are based on propagating the land surface model forward in time from the previous analysis time step. The Forecast_Data group does not contain a medium-range (5-day) forecast of land surface conditions. Soil moisture and temperature values are snapshots/instantaneous data. Time and space coordinate information is stored in the HDF5 root data group.

Table 3. Data Fields for Forecast_Data group
Data Field Name Type Shape Unit Valid Min Valid Max Fill Value
sm_profile_forecast Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_rootzone_forecast Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
sm_surface_forecast Float32 LatCell_LonCell_Array m3 m-3 0.0 0.9 -9999.0
soil_temp_layer1_forecast Float32 LatCell_LonCell_Array K 210.0 340.0 -9999.0
surface_temp_forecast Float32 LatCell_LonCell_Array K 180.0 350.0 -9999.0
tb_h_forecast Float32 LatCell_LonCell_Array K 100.0 350.0 -9999.0
tb_h_forecast_ensstd Float32 LatCell_LonCell_Array K 0.0 50.0 -9999.0
tb_v_forecast Float32 LatCell_LonCell_Array K 100.0 350.0 -9999.0
tb_v_forecast_ensstd Float32 LatCell_LonCell_Array K 0.0 50.0 -9999.0
cell_column1 Unsigned32 LatCell_LonCell_Array dimensionless 0 3855 4294967294
cell_lat1 Float32 LatCell_LonCell_Array degrees -90.0 90.0 -9999.0
cell_lon1 Float32 LatCell_LonCell_Array degrees -180.0 180.0 -9999.0
cell_row1 Unsigned32 LatCell_LonCell_Array dimensionless 0 1623 4294967294
time1 Float64 LatCell_LonCell_Array seconds since 2000-01-01 11:58:55.816 N/A N/A N/A

Observations_Data [top]

Table 4 describes the data fields in the Observations_Data group stored in the aup file collection. This group provides information about the assimilated SMAP observations. Time and space coordinate information is stored in the HDF5 root data group.

Table 4. Data Fields for Observations_Data group
Data Field Name Type Shape Unit Valid Min Valid Max Fill Value
tb_h_obs Float32 LatCell_LonCell_Array K 100.0 350.0 -9999.0
tb_h_obs_assim Float32 LatCell_LonCell_Array K 100.0 350.0 -9999.0
tb_h_obs_errstd Float32 LatCell_LonCell_Array K 0.0 50.0 -9999.0
tb_h_obs_time_sec Float64 LatCell_LonCell_Array seconds 465156000 946000000 -9999.0
tb_h_orbit_flag Unsigned32 LatCell_LonCell_Array dimensionless 0 2 4294967294
tb_h_resolution_flag Unsigned32 LatCell_LonCell_Array dimensionless 1 2 4294967294
tb_v_obs Float32 LatCell_LonCell_Array K 100.0 350.0 -9999.0
tb_v_obs_assim Float32 LatCell_LonCell_Array K 100.0 350.0 -9999.0
tb_v_obs_errstd Float32 LatCell_LonCell_Array K 0.0 50.0 -9999.0
tb_v_obs_time_sec Float64 LatCell_LonCell_Array seconds 465156000 946000000 -9999.0
tb_v_orbit_flag Unsigned32 LatCell_LonCell_Array dimensionless 0 2 4294967294
tb_v_resolution_flag Unsigned32 LatCell_LonCell_Array dimensionless 1 2 4294967294
cell_column1 Unsigned32 LatCell_LonCell_Array dimensionless 0 3855 4294967294
cell_lat1 Float32 LatCell_LonCell_Array degrees -90.0 90.0 -9999.0
cell_lon1 Float32 LatCell_LonCell_Array degrees -180.0 180.0 -9999.0
cell_row1 Unsigned32 LatCell_LonCell_Array dimensionless 0 1623 4294967294
time1 Float64 LatCell_LonCell_Array seconds since 2000-01-01 11:58:55.816 N/A N/A N/A

Land-Model-Constants_Data [top]

Table 5 describes the data fields in the Land-Model-Constants_Data group stored in the lmc file collection. This group contains fields that specify static/time-invariant parameters (or constants) of the Catchment Land Surface Model (CLSM) and its associated L-band Microwave Radiative Transfer Model (MWRTM). Time and space coordinate information is stored in the HDF5 root data group.

Note: Due to the time-invariant nature of the file contents, the lmc file collection consists of only one granule per data product version (as identified by a distinct Science Version ID).

Table 5. Data Fields for Land-Model-Constants_Data group
Data Field Name Type Shape Unit Valid Min Valid Max Fill Value
cell_elevation Float32 LatCell_LonCell_Array m -500.0 6000.0 -9999.0
cell_land_fraction Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
clsm_cdcr Float32 LatCell_LonCell_Array kg m-2 30.0 3000.0 -9999.0
clsm_cdcr Float32 LatCell_LonCell_Array kg m-2 200.0 6000.0 -9999.0
clsm_dzgt Float32 LatCell_LonCell_Array m 0.0988 0.0988 -9999.0
clsm_dzgt Float32 LatCell_LonCell_Array m 0.1952 0.1952 -9999.0
clsm_dzgt Float32 LatCell_LonCell_Array m 0.3859 0.3859 -9999.0
clsm_dzgt Float32 LatCell_LonCell_Array m 0.7626 0.7626 -9999.0
clsm_dzgt Float32 LatCell_LonCell_Array m 1.5071 1.5071 -9999.0
clsm_dzgt Float32 LatCell_LonCell_Array m 10.0 10.0 -9999.0
clsm_dzpr Float32 LatCell_LonCell_Array m 1.33 10.0 -9999.0
clsm_dzrz Float32 LatCell_LonCell_Array m 1.0 1.0 -9999.0
clsm_dzsf Float32 LatCell_LonCell_Array m 0.05 0.05 -9999.0
clsm_dztsurf Float32 LatCell_LonCell_Array m 0.0 0.05 -9999.0
clsm_poros Float32 LatCell_LonCell_Array m3 m-3 0.3 0.9 -9999.0
clsm_wp Float32 LatCell_LonCell_Array m3 m-3 0.001 0.3 -9999.0
mwrtm_bh Float32 LatCell_LonCell_Array dimensionless 0.0 0.7 -9999.0
mwrtm_bv Float32 LatCell_LonCell_Array dimensionless -0.15 0.85 -9999.0
mwrtm_lewt Float32 LatCell_LonCell_Array kg m-2 0.0 1.0 -9999.0
mwrtm_omega Float32 LatCell_LonCell_Array dimensionless 0.0 0.3 -9999.0
mwrtm_poros Float32 LatCell_LonCell_Array m3 m-3 0.3 0.9 -9999.0
mwrtm_rghhmax Float32 LatCell_LonCell_Array dimensionless 0.0 3.0 -9999.0
mwrtm_rghhmin Float32 LatCell_LonCell_Array dimensionless 0.0 2.0 -9999.0
mwrtm_rghnrh Float32 LatCell_LonCell_Array dimensionless 0.0 1.75 -9999.0
mwrtm_rghnrv Float32 LatCell_LonCell_Array dimensionless -1.0 2.0 -9999.0
mwrtm_rghpolmix Float32 LatCell_LonCell_Array dimensionless 0.0 0.0 -9999.0
mwrtm_rghwmax Float32 LatCell_LonCell_Array m3 m-3 0.3 0.9 -9999.0
mwrtm_rghwmin Float32 LatCell_LonCell_Array m3 m-3 0.1 0.4 -9999.0
mwrtm_sand Float32 LatCell_LonCell_Array dimensionless 0.0 1.0 -9999.0
mwrtm_soilcls Unsigned32 LatCell_LonCell_Array dimensionless 1 253 4294967294
mwrtm_vegcls Unsigned32 LatCell_LonCell_Array dimensionless 1 16 4294967294
mwrtm_wangwp Float32 LatCell_LonCell_Array m3 m-3 0.0 0.4 -9999.0
mwrtm_wangwt Float32 LatCell_LonCell_Array m3 m-3 0.1 0.4 -9999.0
cell_column1 Unsigned32 LatCell_LonCell_Array dimensionless 0 3855 4294967294
cell_lat1 Float32 LatCell_LonCell_Array degrees -90.0 90.0 -9999.0
cell_lon1 Float32 LatCell_LonCell_Array degrees -180.0 180.0 -9999.0
cell_row1 Unsigned32 LatCell_LonCell_Array dimensionless 0 1623 4294967294
time1 Float64 LatCell_LonCell_Array seconds since 2000-01-01 11:58:55.816 N/A N/A N/A


Data Field Definitions [top]

Table 6 lists all Level-4 soil moisture data fields and their definitions. All fields are two-dimensional and Float32 unless otherwise indicated in the description.

Table 6. Description of Data Fields for SPL4SMP
Data Field Name GEOS-5 Name Data group Description

baseflow_flux

BASEFLOW Geophysical Baseflow

cell_column

CELL_COLUMN_INDEX [All Data groups]1 The column index of each cell in the cylindrical 9 km Earth-fixed EASE-Grid 2.0. Type is Unsigned32.

cell_elevation

CELL_ELEVATION LandModel Constants Mean elevation above sea Level-of land within each grid cell.

cell_land_fraction

FRLAND LandModel Constants Area fraction of land within each grid cell.

cell_lat

LATITUDE [All Data groups]1 The geodetic latitude of the center of each cell in the cylindrical 9 km Earth-fixed EASE-Grid 2.0. Zero latitude represents the Equator. Positive latitudes represent locations North of the Equator. Negative latitudes represent locations South of the Equator.

cell_lon

LONGITUDE [All Data groups]1 The geodetic longitude of the center of each cell in the cylindrical 9 km Earth-fixed EASE-Grid 2.0. Zero longitude represents the Prime Meridian. Positive longitudes represent locations to the East of the Prime Meridian. Negative longitudes represent locations to the West of the Prime Meridian.

cell_row

CELL_ROW_INDEX [All Data groups]1 The row index of each cell in the cylindrical 9 km Earth-fixed EASE-Grid 2.0. Type is Unsigned32.

clsm_cdcr1

CLSM_cdcr1 LandModel Constants Catchment model: Catchment deficit at which baseflow ceases

clsm_cdcr2

CLSM_cdcr2 LandModel Constants Catchment model: Maximum water holding capacity of land field

clsm_dzgt1

CLSM_dzgt1 LandModel Constants Catchment model: Thickness of soil heat diffusion model layer 1

clsm_dzgt2

CLSM_dzgt2 LandModel Constants Catchment model: Thickness of soil heat diffusion model layer 2

clsm_dzgt3

CLSM_dzgt3 LandModel Constants Catchment model: Thickness of soil heat diffusion model layer 3

clsm_dzgt4

CLSM_dzgt4 LandModel Constants Catchment model: Thickness of soil heat diffusion model layer 4

clsm_dzgt5

CLSM_dzgt5 LandModel Constants Catchment model: Thickness of soil heat diffusion model layer 5

clsm_dzgt6

CLSM_dzgt6 LandModel Constants Catchment model: Thickness of soil heat diffusion model layer 6

clsm_dzpr

CLSM_dzpr LandModel Constants Catchment model: Thickness of profile soil moisture layer (“depth-to-bedrock” in the Catchment model)

clsm_dzrz

CLSM_dzrz LandModel Constants Catchment model: Thickness of root zone soil moisture layer

clsm_dzsf

CLSM_dzsf LandModel Constants Catchment model: Thickness of surface soil moisture layer

clsm_dztsurf

CLSM_DZTSURF LandModel Constants Catchment model: Thickness of soil layer associated with surface_temp

clsm_poros

CLSM_poros LandModel Constants Catchment model: Soil porosity

clsm_wp

CLSM_WP LandModel Constants Catchment model: Soil wilting point

heat_flux_ground

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

heat_flux_latent

LHLAND Geophysical Latent heat flux from land2

heat_flux_sensible

SHLAND Geophysical Sensible heat flux from land2

height_lowatmmodlay

HLML Geophysical Center height of lowest atmospheric model layer

land_evapotranspiration_flux

EVLAND Geophysical Evapotranspiration from land2

land_fraction_saturated

FRSAT Geophysical Fractional land area that is saturated and snow-free2

land_fraction_snow_covered

FRSNO Geophysical Fractional land area that is snow-covered2

land_fraction_unsaturated

FRUNSAT Geophysical Fractional land area that is unsaturated (but non-wilting) and snow-free2

land_fraction_wilting

FRWLT Geophysical Fractional land area that is wilting and snow-free2

leaf_area_index

LAI Geophysical Vegetation leaf area index

mwrtm_bh

MWRTM_BH LandModel Constants Microwave radiative transfer model: H-pol. Vegetation b parameter

mwrtm_bv

MWRTM_BV LandModel Constants Microwave radiative transfer model: V-pol. Vegetation b parameter

mwrtm_clay

MWRTM_CLAY LandModel Constants Microwave radiative transfer model: Clay fraction

mwrtm_lewt

MWRTM_LEWT LandModel Constants Microwave radiative transfer model: Parameter to transform leaf area index into vegetation water content

mwrtm_omega

MWRTM_OMEGA LandModel Constants Microwave radiative transfer model: Scattering albedo

mwrtm_poros

MWRTM_POROS LandModel Constants Microwave radiative transfer model: Porosity

mwrtm_rghhmax

MWRTM_RGHHMAX LandModel Constants Microwave radiative transfer model: Maximum microwave roughness parameter

mwrtm_rghhmin

MWRTM_RGHHMIN LandModel Constants Microwave radiative transfer model: Minimum microwave roughness parameter

mwrtm_rghwmax

MWRTM_RGHWMAX LandModel Constants Microwave radiative transfer model: Soil moisture value above which minimum microwave roughness parameter is used

mwrtm_rghwmin

MWRTM_RGHWMIN LandModel Constants Microwave radiative transfer model: Soil moisture value below which maximum microwave roughness parameter is used

mwrtm_rghnrh

MWRTM_RGHNRH LandModel Constants Microwave radiative transfer model: H-pol. Exponent for rough reflectivity parameterization

mwrtm_rghnrv

MWRTM_RGHNRV LandModel Constants Microwave radiative transfer model: V-pol. Exponent for rough reflectivity parameterization

mwrtm_rghpolmix

MWRTM_RGHPOLMIX LandModel Constants Microwave radiative transfer model: Polarization mixing parameter

mwrtm_sand

MWRTM_SAND LandModel Constants Microwave radiative transfer model: Sand fraction

mwrtm_soilcls

MWRTM_SOILCLS LandModel Constants Microwave radiative transfer model: Soil class. Type is Unsigned32.

mwrtm_vegcls

MWRTM_VEGCLS LandModel Constants Microwave radiative transfer model: Vegetation class. Type is Unsigned32.

mwrtm_wangwp

MWRTM_WANGWP LandModel Constants Microwave radiative transfer model: Wang dielectric model wilting point soil moisture

mwrtm_wangwt

MWRTM_WANGWT LandModel Constants Microwave radiative transfer model: Wang dielectric model transition soil moisture

net_downward_longwave_flux

LWLAND Geophysical Net downward longwave flux over land2

net_downward_shortwave_flux

SWLAND Geophysical Net downward shortwave flux over land2

overland_runoff_flux

RUNOFF Geophysical Overland (surface) runoff (including throughflow)2

precipitation_total_surface_flux

PRECTOT Geophysical Total surface precipitation (incl. snow fall)

radiation_longwave_absorbed_flux

LWGAB Geophysical Absorbed (downward) longwave radiation at the surface

radiation_shortwave_downward_flux

SWGDN Geophysical Downward shortwave flux incident on the surface

sm_profile

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

sm_profile_pctl

PRMC_PRCNTL Geophysical

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

Note: An improved version of the model-only Nature Run (NRv4.1) simulation is used to derive (i) the brightness temperature scaling parameters, (ii) the 31 March 2015, 00:00 UTC model soil moisture initial conditions, and (iii) the soil moisture climatology used to generate the soil moisture output in percentile units (sm_rootzone_pctl, sm_profile_pctl). The NRv4.1 simulation is driven with surface meteorological forcing data from the GEOS-5.12.4 Forward-Processing for Instrument Teams (FP-IT) product for 2000-2014. This newer version of the FP-IT product is more consistent (than the GEOS-5.9.1 FP-IT product used for NRv4 in the Version 2 algorithm) with the near-real-time GEOS-5.13 and GEOS-5.16 Forward Processing (FP) product that is used to generate the Level-4 soil moisture product (2015-present).

sm_profile_wetness

GWETPROF Geophysical Total profile soil wetness (0 cm to model bedrock depth; wetness units5)

sm_profile_wetness_analysis

GWETPROF_ANA Analysis Analysis total profile soil moisture (0 cm to model bedrock depth ; wetness units5)

sm_profile_wetness_analysis_ensstd

GWETPROF_ANA_ENSSTD Analysis Uncertainty of analysis total profile soil moisture (0 cm to model bedrock depth; ensemble std-dev; wetness units5)

sm_profile_wetness_forecast

GWETPROF_FCST Forecast Catchment model forecast total profile soil moisture (0 cm to model bedrock depth; wetness units5)

sm_rootzone

RZMC Geophysical Root zone soil moisture (0-100 cm)

sm_rootzone_pctl

RZMC_PRCNTL Geophysical

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

Note: An improved version of the model-only Nature Run (NRv4.1) simulation is used to derive (i) the brightness temperature scaling parameters, (ii) the 31 March 2015, 00:00 UTC model soil moisture initial conditions, and (iii) the soil moisture climatology used to generate the soil moisture output in percentile units (m_profile_pctl, sm_rootzone_pctl). The NRv4.1 simulation is driven with surface meteorological forcing data from the GEOS-5.12.4 Forward-Processing for Instrument Teams (FP-IT) product for 2000-2014. This newer version of the FP-IT product is more consistent (than the GEOS-5.9.1 FP-IT product used for NRv4 in the Version 2 algorithm) with the near-real-time GEOS-5.13 and GEOS-5.16 Forward Processing (FP) product that is used to generate the Level-4 soil moisture product (2015-present).

sm_rootzone_wetness

GWETROOT Geophysical Root zone soil wetness (0-100 cm; wetness units5)

sm_rootzone_wetness_analysis

GWETROOT_ANA Analysis Analysis root zone soil moisture (0-100 cm; wetness units5)

sm_rootzone_wetness_analysis_ensstd

GWETROOT_ANA_ENSSTD Analysis Uncertainty of analysis root zone soil moisture (0-100 cm; ensemble std-dev; wetness units5)

sm_rootzone_wetness_forecast

GWETROOT_FCST Forecast Catchment model forecast root zone soil moisture (0-100 cm; wetness units5)

sm_surface

SFMC Geophysical Top layer soil moisture (0-5 cm)

sm_surface_wetness

GWETTOP Geophysical Top layer soil wetness (0-5 cm; wetness units5)

sm_surface_wetness_analysis

GWETTOP_ANA Analysis Analysis surface soil moisture (0-5 cm; wetness units5)

sm_surface_wetness_analysis_ensstd

GWETTOP_ANA_ENSSTD Analysis Uncertainty of analysis surface soil moisture (0-5 cm; ensemble std-dev; wetness units5)

sm_surface_wetness_forecast

GWETTOP_FCST Forecast Catchment model forecast surface soil moisture (0-5 cm; wetness units5)

snow_depth

SNODP Geophysical Snow depth within snow-covered land fraction of grid cell2

snow_mass

SNOMAS Geophysical Average snow mass (or snow water equivalent) over land fraction of grid cell2

snow_melt_flux

SNOMLT Geophysical Snowmelt2

snowfall_surface_flux

PRECSNO Geophysical Surface snow fall

soil_temp_layer1

TSOIL1 Geophysical Soil temperature in layer 1 of soil heat diffusion model

soil_temp_layer1_analysis

TSOIL1_ANA Analysis Analysis soil temperature in layer 1 of soil heat diffusion model

soil_temp_layer1_analysis_ensstd

TSOIL1_ANA_ENSSTD Analysis Uncertainty of analysis soil temperature in layer 1 of soil heat diffusion model (ensemble std-dev)

soil_temp_layer1_forecast

TSOIL1_FCST Forecast Catchment model forecast soil temperature in layer 1 of soil heat diffusion model

soil_temp_layer2

TSOIL2 Geophysical Soil temperature in layer 2 of soil heat diffusion model

soil_temp_layer3

TSOIL3 Geophysical Soil temperature in layer 3 of soil heat diffusion model

soil_temp_layer4

TSOIL4 Geophysical Soil temperature in layer 4 of soil heat diffusion model

soil_temp_layer5

TSOIL5 Geophysical Soil temperature in layer 5 of soil heat diffusion model

soil_temp_layer6

TSOIL6 Geophysical Soil temperature in layer 6 of soil heat diffusion model

soil_water_infiltration_flux

QINFIL Geophysical Soil water infiltration rate

specific_humidity_lowatmmodlay

QLML Geophysical Air specific humidity at center height of lowest atmospheric model layer

surface_pressure

PS Geophysical Surface pressure

surface_temp

TSURF Geophysical Mean land surface temperature (incl. snow-covered land area)2

surface_temp_analysis

TSURF_ANA Analysis Analysis surface temperature

surface_temp_analysis_ensstd

TSURF_ANA_ENSSTD Analysis Uncertainty of analysis surface temperature (ensemble std-dev)

surface_temp_forecast

TSURF_FCST Forecast Catchment model forecast surface temperature

tb_h_forecast

TBHCOMP_FCST Forecast Composite resolution Catchment model forecast 1.41 GHz H-pol brightness temperature4

tb_h_forecast_ensstd

TBHCOMP_FCST_ ENSSTD Forecast Uncertainty (ensemble std-dev) of tb_h_forecast4

tb_h_obs

TBHCOMP_OBS Observations

Composite resolution observed (SPL2SMAP or SPL1CTB) H-pol brightness temperature, represented as the average of fore and aft observations from the SMAP antenna3

Note: These brightness temperature observations passed all quality control steps but could not be assimilated for lack of brightness temperature scaling parameters. For such observations, the variables tb_h_obs_assim and tb_v_obs_assim are equal to no-data values.

tb_h_obs_assim

TBHCOMP_OBS_ASSIM Observations

Assimilated value after model-based quality control and climatological adjustment (scaling) tb_h_obs3 for consistency with the land model’s seasonally varying mean brightness temperature climatology

Output for this field is only stored at times and locations for which input SMAP Level-1 or Level-2 data are assimilated. If more than one overpass occurs for a given grid cell within the assimilation window, the Level-1 or Level-2 observations from all overpasses within the analysis update time window are averaged.

Note: These brightness temperature observations passed all quality control steps but could not be assimilated for lack of brightness temperature scaling parameters. For such observations, the variables tb_h_obs_assim and tb_v_obs_assim are equal to no-data values.

tb_h_obs_errstd

TBHCOMP_OBS_ERRSTD Observations Observation error std-dev for tb_h_obs_scaled3

tb_h_obs_time_sec

TBHCOMP_OBS_TIME_SEC Observations

Time values as counts of International System (SI) seconds based on the J2000 epoch in Ephemeris Time (ET). The J2000 epoch starting point is January 1, 2000 at 12:00 ET, which translates to January 1, 2000 at 11:58:55.816 Universal Coordinated Time (UTC). Type is Float64.

Time stamps for H-polarization and V-polarization observations are provided in the fields tb_h_obs_time_sec and tb_v_obs_time_sec, respectively. If observations from more than one overpass time at the same location (grid cell) are assimilated, the observation time stamps reflect the average over the spacecraft overpass times. Furthermore, the fields tb_h_orbit_flag and tb_v_orbit_flag indicate whether the observation is exclusively from ascending orbits (orbit_flag=1), exclusively from descending orbits (orbit_flag=2), or from an average over ascending and descending orbits (orbit_flag=0). The latter case may occur at very high latitudes.

tb_h_orbit_flag

TBHCOMP_ORBFLAG Observations

Flag indicating the orbit direction of H-pol brightness temperature composite fields (tb_h_obs, tb_h_forecast, etc.): 0=average over ascending and descending orbits, 1=ascending orbits only, 2=descending orbits only, Type is Unsigned32.

Time stamps for H-polarization and V-polarization observations are provided in the fields tb_h_obs_time_sec and tb_v_obs_time_sec, respectively. If observations from more than one overpass time at the same location (grid cell) are assimilated, the observation time stamps reflect the average over the spacecraft overpass times. Furthermore, the fields tb_h_orbit_flag and tb_v_orbit_flag indicate whether the observation is exclusively from ascending orbits (orbit_flag=1), exclusively from descending orbits (orbit_flag=2), or from an average over ascending and descending orbits (orbit_flag=0). The latter case may occur at very high latitudes.

tb_h_resolution_flag

TBHCOMP_RESFLAG Observations

Flag indicating the effective resolution of H-pol brightness temperature composite fields (tb_h_obs, tb_h_forecast, etc.): 1=36 km, 2=9 km. Type is Unsigned32.

The fields tb_h_resolution_flag and tb_v_resolution_flag indicate whether the model forecast brightness temperature for a given grid cell corresponds to a 36 km observation from the SPL1CTB product or to a 9 km observation from the SPL2SMAP product. Model forecast brightness temperatures that correspond to 36 km observations from the SPL1CTB product are aggregated from 9 km to 36 km and then posted at 9 km for convenience. Brightness temperature output is only stored at times and locations for which input SPL1CTB or SPL2SMAP brightness temperature data are assimilated. If more than one overpass occurs for a given grid cell within the assimilation window, the latest overpass time prevails.

tb_v_forecast

TBVCOMP_FCST Forecast Composite resolution Catchment model forecast 1.41 GHz V-pol brightness temperature4

tb_v_forecast_ensstd

TBVCOMP_FCST_ENSSTD Forecast Uncertainty (ensemble std-dev) of tb_v_forecast4

tb_v_obs

TBVCOMP_OBS Observations

Composite resolution observed (SPL2SMAP or SPL1CTB) V-pol brightness temperature, represented as the average of fore and aft observations from the SMAP antenna3

Output for this field is only stored at times and locations for which input SMAP Level-1 or Level-2 data are assimilated. If more than one overpass occurs for a given grid cell within the assimilation window, the Level-1 or Level-2 observations from all overpasses within the analysis update time window are averaged.

Note: These brightness temperature observations passed all quality control steps but could not be assimilated for lack of brightness temperature scaling parameters. For such observations, the variables tb_h_obs_assim and tb_v_obs_assim are equal to no-data values.

tb_v_obs_assim

TBVCOMP_OBS_ASSIM Observations

Assimilated value after model-based quality control and climatological adjustment (scaling) of tb_v_obs3 for consistency with the land model’s seasonally varying mean brightness temperature climatology

Note: These brightness temperature observations passed all quality control steps but could not be assimilated for lack of brightness temperature scaling parameters. For such observations, the variables tb_h_obs_assim and tb_v_obs_assim are equal to no-data values.

tb_v_obs_errstd

TBVCOMP_OBS_ERRSTD Observations Observation error std-dev for tb_v_obs_scaled3

tb_v_obs_time_sec

TBVCOMP_OBS_TIME_SEC Observations

Time values as counts of International System (SI) seconds based on the J2000 epoch in Ephemeris Time (ET). The J2000 epoch starting point is January 1, 2000 at 12:00 ET, which translates to January 1, 2000 at 11:58:55.816 Universal Coordinated Time (UTC). Type is Float64.

Time stamps for H-polarization and V-polarization observations are provided in the fields tb_h_obs_time_sec and tb_v_obs_time_sec, respectively. If observations from more than one overpass time at the same location (grid cell) are assimilated, the observation time stamps reflect the average over the spacecraft overpass times. Furthermore, the fields tb_h_orbit_flag and tb_v_orbit_flag indicate whether the observation is exclusively from ascending orbits (orbit_flag=1), exclusively from descending orbits (orbit_flag=2), or from an average over ascending and descending orbits (orbit_flag=0). The latter case may occur at very high latitudes.

tb_v_orbit_flag

TBVCOMP_ORBFLAG Observations

Flag indicating the orbit direction of V-pol brightness temperature composite fields (tb_v_obs, tb_v_forecast, etc.): 0=average over ascending and descending orbits, 1=ascending orbits only, 2=descending orbits only. Type is Unsigned32.

Time stamps for H-polarization and V-polarization observations are provided in the fields tb_h_obs_time_sec and tb_v_obs_time_sec, respectively. If observations from more than one overpass time at the same location (grid cell) are assimilated, the observation time stamps reflect the average over the spacecraft overpass times. Furthermore, the fields tb_h_orbit_flag and tb_v_orbit_flag indicate whether the observation is exclusively from ascending orbits (orbit_flag=1), exclusively from descending orbits (orbit_flag=2), or from an average over ascending and descending orbits (orbit_flag=0). The latter case may occur at very high latitudes.

tb_v_resolution_flag

TBVCOMP_RESFLAG Observations

Flag indicating the effective resolution of V-pol brightness temperature composite fields (tb_v_obs, tb_v_forecast, etc..): 1=36 km, 2=9 km. Type is Unsigned32.The fields tb_h_resolution_flag and tb_v_resolution_flag indicate whether the model forecast brightness temperature for a given grid cell corresponds to a 36 km observation from the SPL1CTB product or to a 9 km observation from the SPL2SMAP product. Model forecast brightness temperatures that correspond to 36 km observations from the SPL1CTB product are aggregated from 9 km to 36 km and then posted at 9 km for convenience. Brightness temperature output is only stored at times and locations for which input SPL1CTB or SPL2SMAP brightness temperature data are assimilated. If more than one overpass occurs for a given grid cell within the assimilation window, the latest overpass time prevails.

temp_lowatmmodlay

TLML Geophysical Air temperature at center height of lowest atmospheric model layer
time TIME [All Data groups]1

Time accrued since 2000-01-01 11:58:55.816. Type is 64-bit floating-point and array is one dimensional.

vegetation_greenness_fraction

GRN Geophysical Vegetation “greenness” or fraction of transpiring leaves averaged over the land area2 of the grid cell.

windspeed_lowatmmodlay

SPEEDLML Geophysical Surface wind speed at center height of lowest atmospheric model layer

1 The time and space coordinate data sets are stored in the HDF5 root data group, not in any particular group (i.e Geophysical_Data).
2 Excluding areas of open water and permanent ice. Output is only stored at times and locations for which input SMAP Level-1 or Level-2 data are assimilated. If more than one overpass occurs for a given grid cell within the assimilation window, output represents average over all overpass times.

3 Observed brightness temperatures that originate from 36 km SPL1CTB files are posted at 9 km here for convenience (as average over fore and aft brightness temperature if stored separately in SPL1CTB product).

4 Model forecast brightness temperatures that correspond to 36 km observations from the SPL1CTB product are aggregated from 9 km to 36 km and then posted at 9 km for convenience.

5 Soil wetness units (dimensionless) vary between 0 and 1, indicating relative saturation between completely dry conditions and completely saturated conditions, respectively.
Soil moisture output in the Geophysical Data (gph) group is provided in three different units:

1. m3/m3 (or volumetric percent): the volume of water / total volume of soil including solids, water, and air
2. dimensionless wetness units (or relative saturation): volume of water / volume of pore space
3. percentile units: root zone and profile soil moisture only (Note: There are known shortcomings in the underlying climatology, and at this time we advise that percentile units be used only with caution).

Soil moisture output in the Analysis Update (aup) group is provided only in m3/m3 (volumetric percent); for applications, the gph output is likely more appropriate. For more details, refer to Appendix D (page 81) of the Product Specification Document (Reichle et al. 2015a).

Metadata [top]

For a description of metadata fields for this product, refer to the Metadata Fields document.

Two-Dimensional Arrays

All SPL4SM HDF5 data fields have LatCell_LonCell_Array shape. This shape is a two-dimensional array, where each data field represents a specific grid cell in the 9 km global cylindrical EASE-Grid 2.0 as specified by the cell_lat and cell_lon arrays. For example, the field surface_temp (234,789) represents the land surface temperature of the grid cell located at cell_lat (234,789) and cell_lon (234,789), where cell_row (234,789)=234 and cell_column (234,789)=789.

Fill/Gap Values [top]

SMAP data products employ fill and gap values to indicate when no valid data appear in a particular data field and ensure that data fields retain the correct shape. Gap values locate portions of a data stream that do not appear in the output data file. Yet because the SPL4SM data product is partially based on modeling, gaps are not expected to occur in the SPL4SM data stream. Note, however, that there might well be 3-hour intervals for which no SMAP data were assimilated. This situation would be reflected in the aup collection when the total number of assimilated observations for the time interval in question is zero.

Fill values appear in the SPL4SM data product over ocean and water surfaces or for variables that are not meaningful (such as snow temperatures in the absence of snow). Fill values are also used, for example, in the aup file collection for all grid cells for which SMAP observations were not assimilated. The latter may occur for any of the following circumstances:

  • There was no SMAP overpass for the grid cell in question during the assimilation time window.
  • The SMAP observations were not available due to quality control, missing science or engineering input data, or any other reason in the Level-1, -2, or -3 processing algorithms.
  • The SMAP observations were rejected for assimilation due to quality control by the SPL4SM algorithm.

SMAP data products employ a specific set of data values to connote that a field is fill. The selected values that represent fill are dependent on the data type.

No valid value in the SPL4SM data product is equal to the values that represent fill. If any exceptions should exist in the future, the SPL4SM content will provide a means for users to discern between fields that contain fill and fields that contain genuine data values.

Notations [top]

Table 7 lists the acronyms and abbreviations used in this document.

Table 7. Acronyms and Abbreviations
Abbreviation Definition
Char 8-bit character
IGBP International Geosphere-Biosphere Programme
Int8 8-bit (1-byte) signed integer
Int16 16-bit (2-byte) signed integer
Int32 32-bit (4-byte) signed integer
Float32 32-bit (4-byte) floating-point integer
Float64 64-bit (8-byte) floating-point integer
H-pol Horizontally polarized
N/A Not Applicable
NF Number of frozen ground pixels
NL Number of water pixels
NT Number of thawed land pixels
NW Number of land pixels
SI International System of Units
SPS Science Production Software
T1, T2 Threshold 1, Threshold 2
TB Brightness Temperature
Uint8 8-bit (1-byte) unsigned integer
Uint16 16-bit (2-byte) unsigned integer
UTC Universal Coordinated Time
V-pol Vertically polarized
VWC Vegetation Water Content