The role of vertical motion structures in the amplification of deep convection

Abstract:

Phases of the convective lifecycle are thought to be associated with variations in the vertical structure of convection. Vertical motion often has a more bottom-heavy profile during growth phases and a more top-heavy profile during decaying phases. During the growth phase of tropical deep convection, the moisture (and moist static energy, MSE) convergence associated with the convection is typically larger than the precipitation, leading to moistening and further enhancements in deep convection. Conversely, during the decaying phase of deep convection, precipitation is usually larger than moisture (and MSE) convergence and hence the atmosphere dries and is less conducive to deep convection. We examine the hypothesis that the variations in vertical motion structure lead to charging and discharging of moist static energy during convective life-cycles.

We also use observations from the TOGA COARE field campaign to test the relative importance of various processes in the growth and decay of moist static energy anomalies. Vertical advection (convergence), horizontal advection, reductions in radiative cooling and increases in evaporation can all play a role. Using filtering and a moist static energy budget analysis, we find that on shorter timescales, variations in vertical structure (and associated vertical advection) are more important to the moist static energy budget than on longer timescales.