Tropical Oceanic Influences on Observed Global Tropical Cyclone Frequency
Although the number of global tropical cyclones (TCs) has been relatively constant from year to year in recent decades, the reason remains unknown. In addition, there is no consensus on whether the frequency of global TCs may change in the future. Using observations from 1980-2021, we found that La Niña is associated with reduced global TC frequency, whereas El Niño is associated with increased global TC frequency.
This research demonstrates that reliable future projections of the El Niño – Southern Oscillation (ENSO) are necessary, but not sufficient, to understand whether global TC frequency may change in the future. Furthermore, this highlights the importance of improving model biases in the tropical Pacific in order to develop more reliable projections of future global TC frequency.
The global tropical cyclone (TC) number 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. Here, we investigated potential links to ocean drivers for years in which observed global TC activity deviated from the mean over the 1980–2021 period. We found that the annual global number of named storm days and accumulated cyclone energy (ACE) were significantly linked with the El Niño – Southern Oscillation (ENSO) and the Atlantic Meridional Mode (AMM). La Niña and positive AMM are associated with the bottom percentiles of both TC metrics and vice versa for El Niño and negative AMM. The ENSO Longitude Index explains variability in annual global named storm days and ACE as well as the Niño 3.4 index.