Influence of African Easterly Wave Suppression on Atlantic Tropical Cyclone Activity in a Convection‐Permitting Model. Issue 22 (15th November 2022)

• Record Type: Journal Article
• Authors: Danso, Derrick K.; Patricola, Christina M.; Bercos‐Hickey, Emily
• Is Part Of: Geophysical research letters. Volume 49:Issue 22(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-15
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL100590
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Plain Language Summary: African easterly waves (AEWs) serve as precursors for tropical cyclones (TC) in the Atlantic. However, it is unclear whether the seasonal TC number is limited by AEWs. To investigate the connection between AEWs and Atlantic TCs, we used an ensemble of regional climate model simulations in which AEWs were either retained or removed. The simulations revealed no changes in the seasonal TC number after removing AEWs. However, the peak of TC genesis was shifted from September to August, suggesting that AEWs could influence the timing of TC genesis. Similarly, removing AEWs led to changes in TC genesis location, with TC genesis increased in the Gulf of Mexico and decreased near the western coast of northern Africa. Finally, by removing AEWs, TCs generated under more favorable atmospheric conditions, suggesting that environmental favorability could be the primary determinant of the seasonal TC number. Thus, AEWs on their own may not be reliable predictors of seasonal TC frequency but may control the variability of the atmospheric environment. Key Points: Suppressing African easterly waves (AEWs) drove no change in seasonal Atlantic tropical cyclone (TC) number in a convection‐permitting model Without AEWs, Atlantic TCs were stronger, formed earlier in the season and further west, and occurred in more favorable environments AEWs may influence the large‐scale atmospheric environment in the Atlantic