Interactions between Tropical Convection and Its Environment: An Energetics Analysis of a 2D Cloud Resolving Simulation

Abstract

The phase relation between the perturbation kinetic energy (K?) associated with the tropical convection and the horizontal-mean moist available potential energy (P) associated with environmental conditions is investigated by an energetics analysis of a numerical experiment. This experiment is performed using a 2D cloud resolving model forced by the Tropical Ocean Global Atmosphere Coupled Ocean?Atmosphere Response Experiment (TOGA COARE) derived vertical velocity. The imposed upward motion leads to a decrease of P through the associated vertical advective cooling, and to an increase of K? through cloud-related processes, feeding the convection. The maximum K? and its maximum growth rate lags and leads, respectively, the maximum imposed large-scale upward motion by about 1?2 h, indicating that convection is phase locked with large-scale forcing. The dominant life cycle of the simulated convection is about 9 h, whereas the timescales of the imposed large-scale forcing are longer than the diurnal cycle. In the convective events, the maximum growth of K? leads the maximum decay of the perturbation moist available potential energy (P?) by about 3 h through vertical heat transport by perturbation circulation, and perturbation cloud heating. The maximum decay of P? leads the maximum decay of P by about 1 h through the perturbation radiative processes, the horizontal-mean cloud heating, and the large-scale vertical advective cooling. Therefore, maximum gain of K? occurs about 4?5 h before maximum decay of P.