Browsing by Author "Chuang, Pi-Yu"

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    How much of Typhoon Morakot’s extreme rainfall is attributable to anthropogenic climate change?
    (International Journal of Climatology, 2019-06-30) Wang, Chung-Chieh; Tseng, Li-Shan; Huang, Chien-Chang; Lo, Shih-How; Chen, Cheng-Ta; Chuang, Pi-Yu; Su, Nan-Chou; Tsuboki, K.
    Typhoon Morakot (2009), which made landfall in Taiwan during August 7–9, 2009, produced the highest rainfall and became the deadliest typhoon ever recorded in Taiwan since 1958. To assess the role of anthropogenic climate change in the typhoon‐related torrent, we compare the water budget between a pair of cloud‐resolving sensitivity experiments. The pair consists of a control simulation that reproduces Typhoon Morakot (2009) in current climate and a sensitivity simulation in which the same storm is placed in a slightly different climate background where the late 20th century anthropogenic climate change signal is removed. The anthropogenic signal is estimated with the CMIP5 experiments of 18 models for the period of 1985–2005, during which the global warming trend is discernible. In climate states that differ merely by a 20‐year mean anthropogenic change, Morakot (2009) yields 3.4–3.6% more total rainfall in the control experiment than its sensitivity counterpart within a radius of 300–500 km from the storm centre. Water budget analysis indicates that the increase in typhoon rainfall is mainly resulted from the enhanced convergence of vapour flux. The enhancement is, in turn, contributed by the increased tropospheric moisture due to global warming and, to a lesser extent, by a more active secondary circulation in the storm that is associated with the anthropogenic climate change.
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    雲解析模式對臺灣梅雨季豪大雨定量降水預報技術之評估研究
    (2015) 莊璧瑜; Chuang, Pi-Yu
    本論文為探討雲解析模式對臺灣梅雨季豪大雨的定量降水預報技術。在2005年之前的梅雨季12-h定量降水預報技術評估中，其結果表示，模式對小雨雨量門檻的預報技術較有掌握，而對中雨及大雨雨量門檻的預報技術不佳（ETS介於0.05～0.15）。 本論文依降雨事件的雨勢規模之不同，將其設計成七個組別，並使用五種技術得分（TS、BS、POD、FAR及OR）和設定13個雨量門檻（0.05、2.5、10、25、50、75、100、130、160、200、250、350及500 mm），評估2012～2014年臺灣梅雨季各組的三天24-h定量降水預報技術，而2.5 km和5 km網格間距的模式預報技術之評估結果較過去十年為佳。 針對不同雨量門檻累計的所有項目（hit、false alarm、miss及correct negative）之總雨量站數後，再計算設計組別的技術得分，由評估結果知，在各雨量門檻，模式對雨勢規模較大的降雨事件之預報技術較雨勢規模較小者為佳，即「當降雨事件的雨勢規模越大時，模式的定量降水預報技術越佳。」且在中高雨量門檻（50～500 mm），模式對規模大的降雨事件之預報技術也較佳，即對可能成災的豪大雨事件預報技術較佳。 本論文另比較2.5 km和5 km網格間距的模式預報技術，其結果表示，當模式解析度提高時，對雨勢規模較大的降雨事件有較佳的預報技術，尤其是在中高雨量門檻（50～500 mm）。同時，在規模大的豪大雨預報不足方面，2.5 km較5 km網格間距的模式預報有所改善，且隨模式預報時間拉長，預報技術降低的速率也較慢。因此，「當模式的解析度提高時，模式對規模大的豪大雨事件之定量降水預報技術較佳。」