Cloud microphysical processes associated with the diurnal variations of tropical convection: A 2D cloud resolving modeling study

Abstract

Cloud microphysical processes associated with the diurnal variations of tropical convection are investigated based on hourly data from a 2D coupled ocean-cloud resolving atmosphere simulation. The model is forced by the large-scale vertical velocity and zonal wind derived from TOGA COARE for a 50-day period. The diurnal composites are carried out in weak diurnal SST variations (case W) and strong diurnal SST signals (case S). The ice water path is larger than the liquid water path in case W than it is in case S. The difference is enhanced in the morning in case W and in the early afternoon in case S when the surface rain rates reach their peaks. Further comparison of cloud microphysics budgets, associated with rainfall peaks, between cases S and W shows that solar heating in case S warms air to reduce the contribution of vapor deposition to cloud growth, which decreases ice water path compared to those in case W. While the collection of cloud water by rain is a major contributor to the surface precipitation in both cases, the melting of precipitation ice (sum of snow and graupel) contributes less to the rainfall in case S than in case W.