Reducing Tropical Cyclone Activity in Global Climate Models by Evaporative Suppression

What would a world without tropical cyclones look like? Although such a world is unrealistic, addressing this question would reveal the role tropical cyclones (TCs) play in modulating the climate system. In this study, we begin to address this question by introducing a novel algorithm for reducing TC activity in TC-permitting global climate models (GCMs) through suppression of wind-induced surface heat exchange (WISHE) at grid points where TC-like conditions are detected. This algorithm, abbreviated as “SWISHE,” was implemented in a suite of GCM simulations developed by NOAA's Geophysical Fluid Dynamics Laboratory and compared to a control suite of simulations with no perturbations. Application of SWISHE resulted in a model-mean 44% reduction of TC frequency compared to control simulations, with TCs of hurricane-strength reduced by approximately 90%. Aggregate analysis of TCs reveals that TCs in the SWISHE simulations are weaker, as peak 10-m horizontal wind speeds decrease by a model-mean of 3.9 m s⁻¹ and minimum sea-level pressures increase by a model-mean of 4.7 hPa. Composite analysis is used to confirm that SWISHE effectively suppressed latent heat fluxes in grid cells with TC-like conditions. The results presented herein are intended to provide a first step in establishing methodology to understand upscale impacts of TCs on the climate system.