未來氣候變化在斯里蘭卡科倫坡大都市區春季極 端降雨事件中的作用;The role of future climate change in springtime extreme rainfall events in Colombo metropolitan region, Sri Lanka

NCUIR > College of Earth Sciences > Taiwan International Graduate Program for Earth System Science (NCU-Academia Sinica) > Electronic Thesis & Dissertation > Item 987654321/86222

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/86222

Title:	未來氣候變化在斯里蘭卡科倫坡大都市區春季極端降雨事件中的作用;The role of future climate change in springtime extreme rainfall events in Colombo metropolitan region, Sri Lanka
Authors:	史朗祺;Koralegedara, Suranjith Bandara
Contributors:	國際研究生博士學位學程
Keywords:	極端降雨;斯里蘭卡;春季;氣候變化;低壓系統;PGW;Extreme rainfall;Sri Lanka;springtime;Climate Change;Low-pressure systems;Pseudo global warming
Date:	2021-10-07
Issue Date:	2021-12-07 12:18:32 (UTC+8)
Publisher:	國立中央大學
Abstract:	由於全球變暖化可能加劇極端天氣事件對社會經濟的影響，特別是在人口稠密的亞洲城市大都市，極端天氣事件受到了極大的關注。與由季風交替形成的熱帶氣旋 (TC)/低壓系統 (LPS) 等極端天氣事件是孟加拉灣地區最重大且災難性的自然災害之一。然而，春季此類極端事件的詳細特徵和未來變化仍不清楚，也是該地區長期存在的問題。因此，本論文旨在了解與 TC/LPS 相關的春季極端降雨事件動力機制及其在斯里蘭卡背景、未來全球變暖情況下的變化及可能影響。使WRF模式降尺度技術 (Weather Research and forecasting model, WRF) 模擬現在與未來暖化條件下的結果。並使用來自本地和遙測的多個觀測系統的數據用於驗證結果。首先，通過歷史春季降雨分析確定了一個獨特的案例研究。其次，對案例研究進行數值模擬和分析。最後，使用PGW（Pseudo Global Warming）方法對當前和未來氣候變暖的事件進行氣候變化影響分析。歷史數據顯示，大約 10% 的春季極端降雨事件與 TC/LPS 相關。這些 TC/LPS 相關事件起源於西南季風肇始，而TC/LPS相關事件之平均日降雨量為其他強降雨事件中最高。分析2016 年 5 月個案數值模擬結果顯示，TC/LPS伴隨極端降雨事件的機制為結合季風西風流、LPS 和局部地形效應交互作用之結果。根據 PGW 模擬，顯示未來更暖的大氣條件會影響 TC/LPS 的發展、極端降雨強度以及位置。TC/LPS在氣候變暖且與現今相似的綜觀天氣下，斯里蘭卡的極端降雨在本世紀中葉相較於現在將增加21%，而到本世紀末增加42%。未來降雨的空間分佈將在中部山區累積。然而，敏感度實驗顯示，未來極端降雨的位置和強度將與駛流場和可用水氣通量具高度敏感，凸顯了熱力和動力作用反饋的重要性。本研究著重詳細研究分析斯里蘭卡極端降雨事件的中尺度動力機制與氣候變化影響。本研究之結果有助於了解熱帶氣候與春季 TC/LPS 相關的極端降雨事件的影響機制。同時顯示將氣候變遷衝擊分析之詳細結果納入未來潛在極端事件之調適和土地利用的重要性，特別是在斯里蘭卡和其他相似地區。 ;There is significant attention on extreme weather events due to their potential in exacerbating the impacts of global warming on socioeconomics, particularly over the highly populated Asian urban metropolises. Extreme weather events associated with Tropical Cyclones (TCs)/Low-Pressure Systems (LPS) modulated by alternating Monsoon flow are among the most significant and disastrous natural hazards over the Bay of Bengal region. However, the detailed characteristics and projected future variability of such extreme events over springtime are still not well understood and a long-standing problem in this region. Thus, this thesis was designed to understand the dynamics of the springtime extreme rainfall events associated with TC/LPS and their variabilities under the future projected global warming for the Sri Lankan context. Analysis was built on downscaling simulations with present-day and projected future conditions using the Weather Research and forecasting model. Data from multiple observational systems, both local and remotely sensed, were used to validate the results. First, a unique case study was identified through a historical springtime rainfall analysis. Second, numerical modeling and analysis on the case study were conducted to analyze the extreme weather event. Finally, the climate change impact analysis of the event comparing the present day and future warming climates was carried out using the Pseudo Global Warming (PGW) method. Historical data show that about 10% of the springtime extreme rainfall events are associated with the TC/LPS. These TC/LPS associated events originated with the southwestern monsoon onset and showed the highest average daily rainfall per event among the other extreme rainfall event types. Detailed numerical analysis on the May 2016 case study revealed that the TC/LPS associated extreme rainfall events has a mechanism combining the SW monsoon westerly flow, LPS flow, and the local topographic effect. According to the PGW simulations, it is indicated that the future warmer atmosphere affects the TC/LPS development, associated extreme rainfall intensity, as well as location. A future TC/LPS in a warming climate with similar synoptic conditions as in the present-day would enhance the extreme rainfall over Sri Lanka by 21% in the mid-century and by 42 % at the end of the century compared to the present day. Spatial distribution of the future rainfall will be accumulated over the central mountains regions. However, sensitivity experiments suggest that the location and the intensity of the future extreme rainfall are highly sensitive to the governing steering flow and the moisture availability, highlighting the importance of the thermodynamic and dynamic feedbacks. This study marks one of the first detailed studies focusing on analyzing mesoscale dynamics and climate change impacts of extreme rainfall events over Sri Lanka. The findings of this research study shall contribute to the scientific knowledge of the springtime TC/LPS related extreme rainfall events in tropical climates. It shall also stress the importance of incorporating the results of detailed climate change impact analysis in managing the potential extreme events and land use in the future, particularly in Sri Lanka and similar localities elsewhere in the world.
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