印度洋北方之孟加拉地區經常遭受熱帶氣旋侵襲。由於當地沿海人口密度高且多為河流及泥沼地，熱帶氣旋所引致之風暴潮往往對當地造成嚴重破壞。如發生於孟加拉灣之1970孟加拉風暴潮，造成近50萬人死亡，為人類史上死亡人數最高之天災。2020年之Amphan氣旋與風暴潮事件，亦造成近13億美元之損失及128人死亡。本研究旨在以台灣COMCOT風暴潮預報系統為基礎，發展適用於印度洋之風暴潮速算系統。於印度洋所發展之熱帶氣旋，其結構與強度有別於太平洋之颱風與大西洋之颶風，因此適用於太平洋與大西洋之風暴潮模式是否適用於求解印度洋之熱帶氣旋型風暴潮為本研究之分析重點。本文以2020 Amphan氣旋為研究案例，分析4種不同參數化風場於風暴潮生成之適用性。分析結果發現，Carr & Elsberry之氣象場於風速剖面、風暴潮溢淹範圍、及時序潮位高程上與觀測資料有最佳之匹配。本研究所採用之COMCOT風暴潮預報系統求解球座標非線性淺水波方程式，搭配巢狀網格系統與移動邊界法，可於沿岸求解高解析度之風暴潮溢淹範圍。同時可結合TPXO全球天文潮模式，以掌握高低潮位對溢淹範圍之影響。本研究建立適用於孟加拉灣氣旋之COMCOT風暴潮速算系統，期待未來對於孟加拉灣地區風暴潮速報及災情掌控有實際之助益。
Developing a storm surge fast calculation system for Indian Ocean
Po-Sen Tseng, Tso-Ren Wu, Chun-Wei Lin, Shu-Chun Chuang, Chia-Chun Hsu, Mei-Hui Chuang
Graduate Institute of Hydrological & Oceanic Sciences, National Central University
The area of Bangladesh in the north of the Indian Ocean is often stroke by tropical cyclones. Due to the high density of local coastal populations, meander rivers, and muddy land, storm surges caused by tropical cyclones often made severe damages. For example, the 1970 Bangladesh storm surge event occurred in the Bay of Bengal caused nearly 500,000 deaths, which is the highest nature hazard death toll in human history. The Amphan cyclone and storm surge events in 2020 also caused nearly US$1.3 billion in losses and 128 deaths. This research aims to develop a storm surge fast calculation system suitable for the Indian Ocean based on the Taiwan COMCOT storm surge forecasting system. The structure and intensity of tropical cyclones developed in the Indian Ocean are different from those of typhoons in the Pacific and hurricanes in the Atlantic. Therefore, whether the storm surge models applicable to the Pacific and Atlantic are suitable for solving tropical cyclone-type storm surges in the Indian Ocean is the focus of this study. This article uses the 2020 Amphan cyclone as a study case to analyze the applicability of four different parameterized wind fields in storm surge generation. The analysis results found that the wind field of Carr & Elsberry has the best match with the observation data in terms of wind speed profile, storm surge flooding area, and time series tide elevation. The COMCOT storm surge forecasting system used in this research solves the nonlinear shallow water wave equation on a spherical coordinate system, with a nested grid system and a moving boundary method. The moving boundary method is able to solve the high-resolution storm surge flooding range along the coast. COMCOT-SS can be combined with the TPXO global tide model to include the influence of tide to the coastal inundation. This study establishes a COMCOT storm surge fast calculation system suitable for the Bay of Bengal. It will be useful for the storm surges forecast and disaster mitigation in the Bay of Bengal in the future.
Keywords: The tropical cyclone in Indian Ocean , Bay of Bangal、Storm Surge、The COMCOT-SS、Inundation、Parametric wind field