臺灣地區劇烈降雨及其與西北太平洋颱風極移和東海沉積紀錄的關係;Extreme rainfalls over Taiwan and their connection with poleward shift of typhoons in western North Pacific and sediment records in East China Sea

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Title:	臺灣地區劇烈降雨及其與西北太平洋颱風極移和東海沉積紀錄的關係;Extreme rainfalls over Taiwan and their connection with poleward shift of typhoons in western North Pacific and sediment records in East China Sea
Authors:	梁庭語;Liang, Ting-Yu
Contributors:	水文與海洋科學研究所
Keywords:	降雨;颱風路徑北轉;沉積物;rainfall;Typhoon track veering northward;sediment
Date:	2017-08-21
Issue Date:	2017-10-27 13:07:23 (UTC+8)
Publisher:	國立中央大學
Abstract:	近幾十年來，西北太平洋地區的颱風路徑和風暴潮顯著北移。本研究使用臺灣地區64年雨量觀測值作為北移的獨立證據。因為臺灣本島對颱風路徑而言獨特的地理位置，颱風產生的降雨趨勢，在西部和北部顯著上升，但東部與東南部上升的較不顯著，肇因於近幾十年颱風往北移動的趨勢。大尺度環境場分析發現，颱風北移是由於導引氣流和西北太平洋副熱帶高壓的減弱，而此減弱的現象是因為熱帶-副熱帶印度-太平洋地區的暖化和季風的減弱，與氣候變遷所造成的熱帶擴張一致。崳山島(120.3E, 26.9N)，位於東海一個孤立的島嶼，在島上湖泊採集一沉積岩芯，發現數個從1930年代以來粗顆粒比例較高的沉積層。分析現地與衛星的雨量資料、再分析資料和颱風路徑資料，發現粗顆粒較多的沉積層，會產生在由梅雨鋒面系統和/或經過東海的颱風所造成的降雨異常強的年。此研究顯示沉積物紀錄有助於了解過去的氣候。 ;A significant poleward shift of tropical cyclones (TCs or typhoons) and TC-induced storm surge in the western North Pacific has occurred in recent decades. Here we use 64-year rainfall observations around Taiwan to provide an independent evidence of the shift. We show that, due to the island’s unique location relative to typhoon tracks, TC-induced rainfall trends are significantly rising west and north of the island but are insignificant east and southeast, caused by a preference in recent decades for TCs to veer more poleward. Analyses of large-scale fields indicate that the TCs’ poleward shift is caused by the weakening of the steering flow and western North Pacific subtropical high, which in turn is due to tropic-subtropical Indo-Pacific warming and a weakened monsoon, consistent with the expansion of the tropics due to climate change. A sediment core collected in the bed of an isolated island lake in the East China Sea (120.3E, 26.9N) shows layers of high concentration of coarse deposition since the 1930’s. We show by analyzing in situ and satellite rainfall data, reanalysis data, and typhoon track data that the coarse-sediment layers were formed in years of anomalously strong precipitations contributed by passages of Mei-Yu fronts and/or typhoons across the East China Sea. Our study shows that sediment records can yield useful insight into the past climate.
Appears in Collections:	[Graduate Institute of Hydrological and Oceanic Sciences] Electronic Thesis & Dissertation

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