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Vertically Integrated Liquid (VIL)

Vertically Integrated Liquid (VIL)

Short Description

Radar-derived estimate of liquid water in a vertical column.



Primary Users


Input Sources

3D Reflectivity Cube


Spatial Resolution: 0.01o Latitude (~1.11 km) x 0.01o Longitude (~1.01 km at 25oN and 0.73 km at 49oN)

Temporal Resolution: 2 minutes

Product Creation

The conversion of weather radar reflectivity data into liquid water content is based on theoretical studies of dropsize distributions and empirical studies on the relationship between reflectivity factor and liquid water content (Greene and Clark 1972).

VIL is a radar-derived estimate of liquid water (exclusive of ice) that is computed at each grid point from the vertical profile of reflectivity using the following equation (Greene and Clark 1972):


where, Z is the radar reflectivity and h is the height expressed in meters. To exclude contributions from ice, if , that term is set to 56 dBZ.

Technical Details

Latest Update: MRMS Version 11.5


Amburn, S. A., and P. L. Wolf, 1997: VIL density as a hail indicator. Wea. Forecasting, 12, 473-478.

Greene, D.R., and R.A. Clark, 1972: Vertically integrated liquid water–A new analysis tool. Mon. Wea. Rev., 100, 548-552.