The Response of Tropical Cyclone Inner Core and Outer Rainband Precipitation to Warming in Idealized Convection-Permitting WRF

Abstract

Global mean and extreme tropical cyclone (TC) precipitation have been increasing over the past few decades and are expected to continue to increase into the future due to climate change. Most projections of future TC precipitation use climate models with grid spacings of 25–100 km, which are too coarse to resolve the convective structures and small-scale precipitation processes within TCs. This work uses convection-permitting Weather Research and Forecasting model simulations to investigate how precipitation and precipitation processes change in the inner core (IC) and outer rainbands (OR) of TCs in response to sea surface temperature (SST) warming. The simulations are idealized, with single TCs initialized from weak vortices over domain-constant SSTs. In these simulations, TC intensity and IC precipitation greatly increase with SST warming while OR precipitation increases slightly. A greater area in the IC is occupied by deep convection more frequently in the warmer simulations, while the deep convective activity remains relatively constant with warming in the TC OR. Mixing ratios of hydrometeors and cloud ice increase with warming in both the IC and OR, while the TCs' vertical circulations deepen, melting levels rise, and mean upward velocities strengthen. This work demonstrates how analysis of three-dimensional storm structures can provide insight into processes that change TC precipitation in different regions of the storm, and future work will include applying this analysis to more realistic convection-permitting simulations.