Fractality in idealized simulations of large-scale tropical cloud systems

Abstract

We simulate the generation of large-scale organized cloud systems with a simple dynamic model containing various cumulus parameterizations in a doubly periodic square domain with 20 700-km sides. The system is without rotation. Starting from a random initial condition, a fractal pattern of clouds is spontaneously generated using a grid-scale representation of cumulus evolution and mesoscale downdrafts. On the other hand, elementary representatives of three traditional types (Kuo, Arakawa-Schubert, and Betts-Miller) of cumulus parameterizations fail to produce fractality. Implications for the cumulus parameterizations arising from cloud fractality are also discussed.