Cumulus-Environment Interaction

An important conceptual breakthrough toward understanding how convection influences the atmosphere on scales larger than the convective elements themselves has come about through the work of Michio Yanai. Yanai et al. (1973) used 1956 Marshall Islands sounding data to diagnose Q1 (apparent heat source) and Q2 (apparent moisture sink) for deep convective systems in this western Pacific region. The quantities Q1 and Q2 had been introduced and defined earlier by Yanai (1961) in a study of the dynamics of typhoon Doris 1958. In the Marshall Islands study, Yanai applied a simplified cloud model that included the processes of entrainment and detrainment to diagnose the bulk properties of cumulus ensembles. This pioneering study provided substantial insight into properties of cloud ensembles and how they impact their environment. The timing of this discovery also allowed it to contribute substantially to the planning of GATE and FGGE and determining how these experiments would be conducted. The idea that observations, particularly data from sounding arrays, can be used to diagnose the collective thermodynamic impacts of ensembles of convection, as well as their impacts on the momentum and vorticity fields, has influenced the course of tropical meteorology over the past four decades. The concepts have been successfully applied to a broad scope of problems in moist convection – to tropical convective systems ranging from trade wind cumulus to the MJO, monsoon convective systems, and midlatitude convective systems.