4:15 PM - 4:30 PM
[AAS01-04] Future changes in tropical and extratropical cyclones affecting Hokkaido using large-ensemble climate simulations
Keywords:Large ensemble simulations, Extreme precipitation events, Tropical cyclones, Extratropical cyclones
Tropical (TC) and extratropical cyclones (ETC) accounts both directly and indirectly to a large fraction of extreme rain events in Hokkaido. Using large-ensemble simulations from the database for Policy Decision making for Future climate change (d4PDF), we investigated how TC and ETC associated precipitation are projected to change in a climate 4-K warmer than pre-industrial levels.
We first examined changes in TC and ETC frequencies. It was revealed that for TCs, a robust decrease throughout the western North Pacific was seen, including those approaching Hokkaido, while only minimal change is projected for ETCs. However, both TCs and ETCs project an increase in precipitation intensity per event, largely attributed to the projected increases in moisture transport and its convergence in response to a warming climate. Additionally, we examined potential changes in cyclone intensity, translation speed, and area, each of which may be critical in determining the cumulative effect of a warming climate for cyclones affecting Hokkaido. TCs approaching Hokkaido showed more events at higher intensities in the 4-K experiment, while ETCs showed minimal if any change in this regard. The change in TC intensity was attributed to both a warmer projected SSTs and decreased vertical wind shear in the 4-K experiment, resulting in TCs maintaining its strength at higher latitudes. Mean TC translation speed decreased by roughly 7%, which was related to a weakened 500-hPa steering flow. ETCs on the other hand showed minimal change (~2%). Lastly, mean cyclone area signaled future shrinkage in both TCs (~8%) and ETCs (~8%).
We first examined changes in TC and ETC frequencies. It was revealed that for TCs, a robust decrease throughout the western North Pacific was seen, including those approaching Hokkaido, while only minimal change is projected for ETCs. However, both TCs and ETCs project an increase in precipitation intensity per event, largely attributed to the projected increases in moisture transport and its convergence in response to a warming climate. Additionally, we examined potential changes in cyclone intensity, translation speed, and area, each of which may be critical in determining the cumulative effect of a warming climate for cyclones affecting Hokkaido. TCs approaching Hokkaido showed more events at higher intensities in the 4-K experiment, while ETCs showed minimal if any change in this regard. The change in TC intensity was attributed to both a warmer projected SSTs and decreased vertical wind shear in the 4-K experiment, resulting in TCs maintaining its strength at higher latitudes. Mean TC translation speed decreased by roughly 7%, which was related to a weakened 500-hPa steering flow. ETCs on the other hand showed minimal change (~2%). Lastly, mean cyclone area signaled future shrinkage in both TCs (~8%) and ETCs (~8%).