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The effects of African easterly wave suppression by wave track on Atlantic tropical cyclones

Presentation Date
Friday, December 15, 2023 at 4:02pm - Friday, December 15, 2023 at 4:13pm
MC - 3005 - West



African easterly waves (AEWs) are synoptic-scale disturbances that propagate across North Africa to the Atlantic Ocean in two tracks north and south of the African easterly jet. These waves are of particular importance because they can serve as seedling disturbances for Atlantic tropical cyclones (TCs). Recent research, however, has shown that AEWs are not necessary to maintain basin-wide TC frequency in the Atlantic. In this study, we further examine the AEW-TC relationship by investigating the effects of AEW suppression by wave track on Atlantic TC activity. To conduct this research, we used the Weather Research and Forecasting (WRF) model to simulate three Atlantic TC seasons. Control simulations were performed in which AEWs entered the regional model domain through the eastern lateral boundary condition. Three additional experiments were then performed in which AEWs were removed from the eastern lateral boundary condition in latitude bands corresponding to the north, south, and both AEW tracks. We found that without AEWs, there was an increase in Atlantic TC activity, with the most pronounced and statistically significant increase occurring when the AEWs were suppressed in the south and both tracks. These changes coincided with more favorable environmental conditions for TCs, including reduced vertical wind shear and increased mid-tropospheric relative humidity. Additionally, 2-10 day disturbances re-emerged ~20o west of the eastern lateral boundary in the region of the south track in the experiments with AEW suppression in the south and both tracks. These disturbances coincided with increased convective activity during TC genesis and point to possible TC genesis mechanisms in the absence of AEWs. Our results indicate that AEWs are not a limiting factor for TCs, and that AEW suppression, specifically in the south track, can affect the large-scale environment to become more favorable for TC genesis.

Funding Program Area(s)