The Thermodynamic Equation in Cumulus Dynamics

Abstract

Neither the pseudo-adiabatic nor the saturation-adiabatic form of the thermodynamic equation used in meteorological practice is suitable for the study of cumulus dynamics inasmuch as this form ignores the microphysics of condensation and precipitation. A thermodynamic equation has been derived treating the cloud as a mixture of dry air, water vapor, and liquid water distributed into droplets, drops and/or other centers of condensation and evaporation. The equation implicitly includes the effect of fallout of the centers from their parent parcels of air and is explicitly supplemented by an equation of continuity for the centers. A simple way has been indicated for extending the basic equation which has been derived for condensation-evaporation centers of uniform mass (and fall velocity relative to air) to clouds having a population of centers of varying mass.