Abstract
Moist Static Energy (MSE) represents the combined effects of moist enthalpy and potential energy in an atmospheric column. Energy balance demands that the net import of radiant and diffusive energy to an atmospheric column is balanced by the divergence of MSE through circulation. Thus, to understand tropical deep convection, such as monsoons, one must investigate, in addition to circulations, the three-dimensional gradient of MSE. Here, using reanalysis data, we decompose a vertical profile of MSE into four terms: its minimum value (h0), and the corresponding pressure level (p0), a component that is symmetric (β), and that is asymmetric (α) about the minimum value. These four degrees of freedom enable us to explain the spatiotemporal variations of the MSE and its divergence in a simplified fashion. The vertically integrated horizontal divergence of MSE flux quantifies the net export of MSE from the atmospheric column, while vertical advection characterizes the upward transport of MSE to upper levels. We show that the climatological MSE transport diagnosed from reanalysis closely resembles that derived from the reconstructed MSE profiles, demonstrating the effectiveness of the proposed framework. Furthermore, alongside the dynamics, we examine the relative contributions of the asymmetric and symmetric components of the MSE profile in modulating the interannual variations of the energy transport, and convection over South Asia and West Africa during the boreal summer, and relate them to climate modes such as the El Niño Southern Oscillation (ENSO), the Tropical Atlantic sea surface temperature (SST) variability, and the Indian Ocean Dipole (IOD).