GRIB-API definition
volumetric Volumetric soil moisture | Abbreviation |
vsm
UERRA details
Definition | Volumetric soil moisture of a soil layer. |
Validity | instantaneous |
Comment |
Averaged volumetric soil moisture between given levels | Sea points should be set as missing values (encoded as bitmap). Soil layers must always start from 1 (0 soil level is the surface by default which is not encoded). To interpret soil moisture and to compare different models the Soil Wetness Index (SWI) is used: SWI = (soil_moisture - wilting_point) / (field_capacity - wilting_point).
Field capacity corresponds to the maximum value that the model can sustain without precipitation for more than a few hours. The vegetated fraction of the soil evaporates at the maximum rate for soil moisture larger than field capacity and stops evaporating below the permanent wilting point, with a continuous variation between the two extremes. All Partners are asked to provide the wilting point and the field capacity for each grid point. |
WMO GRIB2 definition
Parameter |
---|
Discipline | 2 | land surface products |
Parameter |
Categorycategory | 0 | vegetation/biomass |
category Numbernumber | 25 | volumetric soil moisture |
Level |
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Type of first fixed surface |
106 | Depth below land surface (m)151 | soil level** |
Scale factor of first fixed surface |
20 | |
Scaled value of first fixed surface |
value in cm | Depth of the top of the layer in 0/1/2/3/.../X-1 | n-1 for the nth soil layer |
cm |
Type of second fixed surface |
106 | Depth below land surface (m)151 | soil level* |
Scale factor of second fixed surface |
20 | |
Scaled value of second fixed surface |
value in cm | Depth of the bottom of the layer in cm1/2/3/.../X | n for the nth soil layer |
**newly approved level type (WMO release in May 2016)