Moisture-continuity equation

From Glossary of Meteorology

moisture-continuity equation

The water vapor storage equation as applied to the atmosphere.

The general form of the equation is written
where I is the atmospheric moisture inflow, E the evapotranspiration from the ground, O the atmospheric moisture outflow, P precipitation, and dS/dt the time rate of change of moisture storage in the portion of the atmosphere under consideration. In practice the equation is more commonly applied to a finite interval of time and the various terms become mean values in this interval.