Tropical Cyclone behaviour and impacts in Southeast Asia, historically and in the warming future

Abstract

Southeast Asia is among the most tropical cyclone‐prone regions worldwide, and will become more susceptible due to rapid growth in population and economy, and potential changes in tropical cyclone (TC) behaviour due to climate change. A thorough insight into how TCs and physical impacts have been changing in the warming climate in this region is essential to better anticipate, manage and act on TC risks. In this dissertation, first a 50‐Year Southeast Asia TC Landfall Climatology (1970 ‐ 2019) is developed considering the TC attribute disparities among four agency datasets. A shorter period (1998 – 2018) of TC wind and rain impacts is then examined. Finally, landfalling TCs during the last 20 years are simulated using current conditions, and then re‐simulated using future climate scenarios SSP2‐4.5 and SSP3‐7.0, downscaled from the CMIP6 ensemble, by applying the Pseudo Global Warming framework to quantify future changes in Southeast Asia TC exposure. Approximately half of western North Pacific TCs make landfall in Southeast Asia. The Philippines and Taiwan are most vulnerable to TC landfall and associated impacts, followed by southern China, northern Vietnam and Laos. In the worst‐case scenario, TCinduced winds can spread hundreds of kilometres inland, and prior to TC landfall, damaging winds can influence areas quite far inland. TC‐related rainfall occurs across almost the entire Southeast Asia region with more persistent intense rain accumulating near the coast and short‐term intense rain occurring in high‐terrain areas far inland. By the end of the 21st century under the SSP3‐7.0 scenario, landfalling TCs are projected to be 8% more intense at landfall, 2.8% faster and have smaller wind and rain fields. However, the mean rainfall within 500 km of the TC centre increases significantly with amplified increases closer to the TC centre. The historical northward shift in TC landfall will continue into the future with extended tracks further inland. TC exposure and related impacts, therefore, significantly increase in the northern Philippines, Taiwan, southern China west of 117 °E, and north Vietnam, spreading toward Laos, and Thailand, and decrease in the southern areas of Southeast Asia and southern China east of 117 °E.