Relationships among deep convective cloud system size, cloud microphysics and atmospheric thermodynamic structure throughout the global tropics

Abstract:

The radiative forcing of deep convective clouds systems plays a key role in the general circulation of the atmosphere by modifying the gradients in heating and cooling of the atmosphere that drive weather systems. A number of factors can be observed to strongly influence the spatial coverage of deep convective clouds systems, and hence the magnitude of their radiative forcing. These include convective aggregation, the level of mesoscale organization of individual cloud systems, the convective available potential energy (CAPE) and vertical shear of the horizontal wind in the cloudy environment, and the microphysics of the cloud. Here we present results from a database of millions of deep convective cloud systems observed by the NASA A-Train of satellite sensors over the entire global tropics. The spatial coverage of isolated deep convective clouds, as well as the combined coverage of the core-anvil structure of large mesoscale convective cloud systems, is related to CAPE, shear, aggregation of convective elements, and the distribution of cloud particle size and phase within cloud boundaries. We describe geographic variations in these relationships and offer observational constraints on these relationships suitable for evaluating climate model parameterizations of the convection and clouds that strongly influence the radiative forcing of the tropical climate. In addition to regional differences in these relationships, we also explore variations evident between El Niño and La Niña conditions.