The Variable Nature of Convection in the Tropics and Subtropics: A Legacy of 16 Years of the TRMM Satellite

Abstract:

For over 16 years, the Precipitation Radar of the Tropical Rainfall Measuring Mission (TRMM) satellite detected the three-dimensional structure of significantly precipitating clouds in the tropics and subtropics. This talk reviews and synthesizes studies using the TRMM radar data to present a global picture of the variation of convection throughout low latitudes. The multi-year dataset shows convection varying not only in amount but also in its very nature across the oceans, continents, islands, and mountain ranges of the tropics and subtropics. Shallow isolated raining clouds are overwhelmingly an oceanic phenomenon. Extremely deep and intense convective elements occur almost exclusively over land. Upscale growth of convection into mesoscale systems takes a variety of forms. Oceanic cloud systems may form by self-aggregation and generally have less intense embedded convection although they can form very wide stratiform regions, generally wider than seen over land. Continental mesoscale systems often have the most intense embedded convection. Some of these most intense convective cells and mesoscale systems occur near the great mountain ranges of low latitudes. The Maritime Continent and Amazonia exhibit convective clouds with maritime characteristics although they are partially or wholly land. Convective systems containing broad stratiform areas manifest most strongly over oceans. The stratiform precipitation occurs in various forms. Often it occurs as quasi-uniform precipitation with strong melting layers connected with intense convection. In monsoons and the intertropical convergence zone, it takes the form of closely packed weak convective elements. Where fronts extend into the subtropics, broad stratiform regions are larger and have lower and sloping melting layers related to the baroclinic origin of the precipitation.