[A-AS02] Extreme Events: Observations and Modeling

[AAS02-10] Increase in the strength of typhoons to Taiwan due to global warming

*Ravi Shankar Pandey¹、Yuei-An Liou¹ (1.National Central University)

キーワード：Cyclogenesis, El Niño Southern Oscillation, Sea Surface Temperature, Sea Surface Temperature Anomaly

Detailed investigation on the tracks and cyclogenesis locations of all 77 typhoons that hit Taiwan in the last 40 years (1977 to 2016) during typhoon season (May to November) is carried out. Ten pathways of all typhoons that hit Taiwan are detected and statistical analysis is carried out on fundamental typhoon parameters, including the direction to enter Taiwan, ocean of cyclogenesis, and phases of El Niño Southern Oscillation (ENSO) at cyclogenesis. The majority (> half, 53 %) of typhoons strike Taiwan from the East direction, typically (78%) from the Philippine Sea. They are on average stronger than the rest two other directional (West, South) typhoons. Yet, typhoons from the West uniquely survive the longest hours with the highest curvy tracks, often (59%) from just bordering the ocean i.e., the South China Sea. They are on average relatively weaker. Further statistical analysis on relationships among all typhoon parameters through Fisher’s Exact and Chi-square (χ2) tests supports the above crucial finding and reveals that the curvy nature of tracks of typhoons is more responsible for the longer survival of typhoons (r = 0.67) than its strength. 26% more cyclogenesis is detected during the warm phase of ENSO than the cold phase. In the last 4 decades during the warm phase of ENSO, the number of cyclogenesis is also observed slowly increasing. A significant rise in the Sea Surface Temperature (SST) by 0.4 ~ 0.7 °C is measured using decadal, 5-yearly, yearly, ENSO phase, and monthly-wise SST Anomalies (SSTA) for the whole typhoon season (May-November) during the last 40 years in comparison to base years (1941-1970) over the entire global ocean, North Pacific Ocean, Philippine Sea, South China sea, and Eastern China Sea. A 35% crucial increase in decadal-averaged strength of typhoons is observed by 0.4 ~ 0.7 °C rise in the SST in all study oceans that originate typhoons to hit Taiwan during the last 40 years (1977 to 2016). The role of El-Niño epochs is found very crucial for the major SSTA changes during the typhoon season. The climatological analysis is fully consistent with statistical findings and leads to global warming as the major cause of the rising strength of typhoons that hit Taiwan during the study period. The maximum SST change in the Eastern China Sea during the study period is potentially due to its proximity from mainland China. This fact opens new research opportunities for the future.