One-Dimensional Time-Dependent Modeling of GATE Cumulonimbus Convection

Abstract

A one-dimensional time-dependent cumulonimbus model is designed that, unlike in previous one-dimensional models, simulates cloud-top heights, vertical velocities, and water contents that are reasonably consistent with those observed in real convective cores. The model successfully simulates deep tropical oceanic cumulonimbus with results that are in agreement with aircraft observations of vertical velocity, observations of radar reflectivity, and three-dimensional model simulations. These results are achieved by improving the parameterizations of the following physical processes: vertical mixing through the inclusion of an overturning thermal circulation near cloud top, lateral entrainment by modifying the assumed shape of the cloud, initiating convection with sustained boundary-layer forcing that resembles the lifting by gust fronts associated with tropical oceanic cumulonimbus, and making the pressure perturbation internally consistent with the horizontal distribution of vertical velocity in the cloud. The effect of a tilted updraft on precipitation fallout and enhanced cloud growth are also examined.