[A-AS04] Advances in Tropical Cyclone Research: Past, Present, and Future

[AAS04-09] Cause of the Recent Tendency of Tropical Cyclones Approaching Coasts as Revealed by HighResMIP-PRIMAVERA Simulations

*Fumiaki Ogawa¹, Shoshiro Minobe¹, Roberts J. Malcolm², Rein Haarsma³, Dian Putrasahan⁴, Christopher D. Roberts⁵, Enrico Scoccimarro⁶, Laurent Terray⁷, Pier Luigi Vidale⁸ (1.Faculty of Science, Hokkaido University, 2.Hadley Centre, Met Office, 3.The Royal Netherlands Meteorological Institute , 4.Max Planck Institute for Meteorology, 5.European Centre for Medium-Range Weather Forecasts, 6.Euro-Mediterranean Center on Climate Change, 7.European Center for Research and Advanced Training in Scientific Computation, 8.Department of Meteorology, University of Reading)

Keywords:tropical cyclones, anthropogenic forcing, natural climate variability, PRIMAVERA

Tropical cyclones developing over the ocean threaten society when they approach land. A recent study found a tendency for tropical cyclones to reach their maximum intensity closer to the coast over the last 40 years. However, whether this trend is due to global warming or natural variability is unclear.

This study aims to identify the cause of the observed trend. To this end, we analyzed the output of a high-resolution global multi-model ensemble prepared by the PRIMAVERA project according to the CMIP6 HighResMIP protocol. We assume that the atmosphere-only simulations reproduce both the responses to anthropogenic forcing and natural climate variability constrained by sea-surface temperature (SST) and that the air-sea coupled simulations reproduce only the forced response although other factors such as SST biases/errors may influence the results. The results show that the atmosphere-only simulations reproduced the observed trend, but the atmosphere-ocean coupled simulations did not. This suggests that the observed trend is not caused by global warming but by natural variability. We find that the relevant natural variability is the Inter-decadal Pacific Oscillation (IPO). A significant contribution to the trend is the variation of tropical cyclone genesis locations associated with IPO in the models, consistent with the results of observation data.