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Tropical Cyclone Frequency: The Role of Seeds and the Large-Scale Environment (Invited)

Presentation Date
Monday, December 12, 2022 at 9:00am - Monday, December 12, 2022 at 9:10am
McCormick Place - E354a



The number of annual global tropical cyclones (TCs) has historically been relatively constant from year-to-year, however, the reason remains unknown. Furthermore, climate projections are inconclusive regarding future global TC frequency changes. To work toward solving this problem, we investigated the role of TC precursor disturbances, or “seeds”, and the large-scale environment in controlling TC frequency. In the first part of this presentation, we examine the relationship between TCs and their seeds in convection-permitting regional climate model simulations in which the typical Atlantic TC seeds, African easterly waves (AEWs), were prescribed or suppressed. The experiments produced no significant change in seasonal Atlantic TC number. Next we investigated the influence of climate change on the relationship between Atlantic TCs and AEWs in global climate model simulations from the High Resolution Model Intercomparison Project. We found that future changes in AEW frequency were not a good indicator of future Atlantic TC activity. Finally, we explored the role of the large-scale environment by analyzing the observed relationship between global TC frequency and tropical ocean variability, and found that the annual global number of named TC days is significantly linked with the El Niño–Southern Oscillation (ENSO). Altogether, this research indicates that the large-scale environment may be a dominant control on TC frequency, with TC seeds playing a minimal role.

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