How the environment interacts with the development and structure of deep tropical convective clouds remains one of the key uncertainties in understanding climate change. Complexities of tropical cloud system development and structure results from the state and evolution of the large-scale variables, including advective forcings, radiative transfer, air-sea interaction, as well as the smaller scale cloud microphysical and turbulent processes (e.g. boundary-layer turbulence). One method to study how the complex environmental and cloud processes contribute to the lifecycle of tropical convective systems is through the utilization of cloud resolving models (CRMs). An advantage of the CRM is its ability to explicitly resolve individual convective cells, while at the same time encompassing an entire cloud system. In addition, observational data can be used to force the CRM to ensure as close an agreement as possible between the bulk properties of the model and the observational data (dependent variables such as temperature and moisture are still free to evolve). By quantifying the cumulative effects of cloud systems, the CRM can be used to study the role in which large-scale advective forcings, radiative transfer, air-sea interactions, and microphysical processes play in the development, maintenance, and structure of tropical cloud systems.
In this study, the Goddard Cumulus Ensemble Model (GCE) is used to examine the behavior and response of air-sea interactions, microphysical and precipitation processes, radiational effects, and large-scale forcings in the evolution of two multi-day tropical convective systems. The first system is over the relatively cool and dry atmosphere of the eastern Atlantic (1-7 September 1974; GATE), while the second is over the warmer and more moist tropical waters of the western Pacific Ocean (19-27 December 1992; TOGA COARE). Both two- and three-dimensional versions of the GCE are used to conduct the simulations, which includes a full three-class ice-phase microphysics scheme, and explicit interactions between the cloud microphysics, radiation, and surface fluxes.
The convective cloud systems from the GATE and TOGA-COARE simulations will be compared which each other in order to evaluate the role of environmental and cloud-scale forcings on tropical convective development. Some results which will be compared and presented from these simulations include (1) quantified heating and moisture budgets in the convective and stratiform regions; (2) domain-averaged mass fluxes, radiation fluxes, surface fluxes, cloud fractions, and precipitation amounts; (3) temperature and moisture deviations from observations; and (4) profiles of the hydrometeor distributions. The simulated results will also be compared to observations in order to quantify the relative significance in which surface processes, radiation, microphysics, large-scale forcings, and domain dimension play in the development and evolution of these systems.