Simulation of Tropical Convective Systems. Part II: Simulations of Moving Cloud Lines

Abstract

The new cumulns parameterization of Part I of this paper is used in a setes of simulations of tropical mesoscale convective lines. The structures and life cycles of the simulated systems are quite similar to those observed in many studies of tropical convection, supporting the use of the parametedzation in mesoscale model. The modeled cloud lines formed extensive upper-level nimbostratus clouds, primarily from air detrained below cloud top by the parameterized convection. These clouds produced copious rainfall and tended to shift the net diabafic heating predicted by the model to higher levels. When a cloud model lacking lateral detrainment was used, the simulated cloud lines grew rapidly, had short lifetimes, did not develop nimbostratus ions and concentrated the diabatic heating in the upper levels. Radiative processes, though crudely simulated, were shownto have potentially large effects on the intensity of the conyective system Decreasing the intercept, No, in the drop size distribution in the explicit moisture scheme had relatively small effects on the structure of the simulated systems, but it inctsed the rainfall and caused a small upward shir in the vertical heating probe.