Influence of African Easterly Wave Suppression on Atlantic Tropical Cyclone Activity in a Convection-Permitting Model
The physical controls on tropical cyclone (TC) frequency remain poorly understood. We investigated the role of the typical Atlantic TC precursor (or “seed”), African easterly waves (AEWs), on seasonal Atlantic TC activity. We performed 3-member ensembles of convection-permitting regional climate model simulations in which AEWs were prescribed or removed from the lateral boundary condition. Suppressing AEWs produced no change in seasonal Atlantic TC frequency, however, TCs were stronger and generated further west.
This research suggests that TC seeds are not a primary control on future TC frequency but can influence TC characteristics.
African easterly waves (AEWs) are strongly linked to Atlantic tropical cyclones (TCs) on the synoptic timescale by serving as seedling disturbances for TC genesis. However, it is unclear whether climatological TC frequency is limited by AEWs. We investigated the impact of suppressing AEWs using a 3-member ensemble of convection-permitting regional model simulations, in which AEWs were either retained or removed through the lateral boundary conditions. Suppressing AEWs did not substantially change seasonal TC number, but did influence TC intensity, genesis time, and location. Suppressing AEWs produced stronger TCs, shifted peak TC genesis from September to August, and reduced (increased) TC genesis in the eastern Atlantic (Gulf of Mexico). Without AEWs, TCs generated under more favorable large-scale atmospheric conditions. These results indicate that AEWs may not be reliable predictors of basin-wide seasonal TC frequency. However, simulations provide evidence that AEWs could influence the large-scale environment that is important for TCs.