Tropical Cyclone Activity in the High‐Resolution Community Earth System Model and the Impact of Ocean Coupling

Abstract

AbstractHigh‐resolution Atmosphere General Circulation Models (AGCMs) are capable of directly simulating realistic tropical cyclone (TC) statistics, providing a promising approach for TC‐climate studies. Active air‐sea coupling in a coupled model framework is essential to capturing TC‐ocean interactions, which can influence TC‐climate connections on interannual to decadal time scales. Here we investigate how the choices of ocean coupling can affect the directly simulated TCs using high‐resolution configurations of the Community Earth System Model (CESM). We performed a suite of high‐resolution, multidecadal, global‐scale CESM simulations in which the atmosphere (∼0.25° grid spacing) is configured with three different levels of ocean coupling: prescribed climatological sea surface temperature (SST) (ATM), mixed layer ocean (SLAB), and dynamic ocean (CPL). We find that different levels of ocean coupling can influence simulated TC frequency, geographical distributions, and storm intensity. ATM simulates more storms and higher overall storm intensity than the coupled simulations. It also simulates higher TC track density over the eastern Pacific and the North Atlantic, while TC tracks are relatively sparse within CPL and SLAB for these regions. Storm intensification and the maximum wind speed are sensitive to the representations of local surface flux feedbacks in different coupling configurations. Key differences in storm number and distribution can be attributed to variations in the modeled large‐scale climate mean state and variability that arise from the combined effect of intrinsic model biases and air‐sea interactions. Results help to improve our understanding about the representation of TCs in high‐resolution coupled Earth system models, with important implications for TC‐climate applications.