Parameter Tree:
EARTH SCIENCE > ATMOSPHERE > CLOUDS > CLOUD MICROPHYSICS > CLOUD PRECIPITABLE WATER

Definition:
The total atmospheric water vapor contained in a vertical column of unit cross-sectional area extending between any two specified levels, commonly expressed in terms of the height to which that water substance would stand if completely condensed and collected in a vessel of the same unit cross section.

Reference:
The Glossary of Weather and Climate, American Meteorological Society, 2014. http://glossary.ametsoc.org/wiki/Precipitable_water