On the local available energy budget of an idealized tropical cyclone

Abstract

Exploring the links between moist processes, convection, and intensification in modeled tropical cyclones (TCs) remains an important object in the TC internal dynamics. In this study, the full life cycle of an idealized TC is diagnosed by a local moist available energy budget. In general, the diabatic term in available potential energy (APE) mainly from the microphysical processes dominates the rapid intensification (RI) of the TC, while the uplift term makes a negative and considerable contribution, implying the importance of water lifting in TC development. The budgets at different layers in the inner region are further explored. In the lower troposphere, the downward transport of the vertical pressure flux dominates the growth of the available elastic energy (AEE); the planetary boundary layer (PBL) and the microphysical processes contribute more to APE in the pre-RI and RI stage, respectively. In the mid-upper troposphere, the diabatic term mainly from the microphysical processes leads to the growth of APE; then the increased APE is converted into mechanical energy and ultimately the cyclone intensifies. The vertical pressure fluxes transport downward below 10 km and upward above 10 km, with the AEE being deposited in the lower troposphere and removed in the mid-upper troposphere. Compared to previous budget analyses, our approach emphasizes the conditional instability of the atmosphere and the corresponding result aligns more closely with the conditional instability of the second kind (CISK) mechanism. Also, the divergence of the APE flux at high levels indicates an instantaneous strengthening of the wind speed model.