| 摘要: | 本計劃書原為國際性「東亞季風觀測實驗台灣參與國際水文觀測實驗計畫」整合計畫之第二分支「冬季降雨觀測實驗」，總主持人原是陳慶昌教授。由於行政程序與時效因素，現由嚴明鉦教授擔任總主持人，陳慶昌教授將擔任本整合計畫之首席協同科學家並保留原創精神主導負責。近年來政府對於台灣豪雨/降雨的研究明顯偏重於颱風，然而牽絆東北部地區的冬季降雨研究卻未受到對等的重視。整個冬季，台灣北部與東北部地區壟罩在連綿的冬雨之下，長時間持續的雨量仍造成不少民生困擾。就在今(2007)年11 月底，台灣東部與北部遭受豪雨侵害，花蓮及宜蘭地區出現山路崩塌與土石流，顯示豪雨災害在冬季也同樣發生。我們透過前導研究發現，發展於台灣東部/東北部海面的台灣低壓（Taiwan low）扮演冬季降雨的關鍵角色，台灣低壓形成自一道距台灣東部約200 公里的低壓淺槽，又稱為「台灣槽」。在東亞大陸寒潮產生後，這道準靜止低壓槽經常被寒潮觸發形成低壓波動，這種波動亦經常發展成低壓系統，並造成台灣東北部的降雨。東亞寒潮除了對台灣影響甚大，對寒潮「下游區」的東南亞國家也具有衝擊。東亞寒潮亦在熱帶東南亞產生綜觀尺度（synoptic-scale）渦旋系統，這些渦旋經常在菲律賓海及南海產生，再緩慢向西移動，經常於秋季影響菲律賓、越南，並於冬季影響印尼、馬來西亞。這些渦旋挾帶充沛降雨，加上移速緩慢，所經之處時常導致豪雨。針對這些冬季天氣現象，我們從數年前即開始著手進行前導研究，累積背景知識，並規劃適當的觀測實驗。我們的前導研究發現，台灣低壓導致了北部地區約四分之三的冬季降雨，但是對下列科學議題需要進行深入探討與驗證：降雨天氣分類—台灣低壓的角色、台灣低壓的成因及發展過程、冬季天氣的多重尺度交互作用。在實驗規劃中我們卻也發現，許多遭受寒潮渦旋侵襲的國家對渦旋系統一無所知，急需要在科學上領先的亞洲國家伸出援手。為了追求這些科學問題的解答、改善對冬季降雨的預報度並輔助國際社會進行氣象研究，吾等提出「冬季降雨觀測實驗（Winter Rainfall Experiment）」整合研究提案。「冬季降雨觀測實驗」提案除了具有實質前導研究作為科學依據之外，並和日本「季風亞洲水文大氣研究及預報行動（MAHASRI）」締結互惠協議，因而與七個國家（日本、越南、泰國、馬來西亞、印尼、菲律賓及美國）及若干國際實驗進行協同觀測，並獲得各國家的觀測協助及資料流通。「冬季降雨觀測實驗」不但能提增觀測資料、降低經費成本，更將提升台灣在亞洲國際的科學地位，以科學進行實質外交。 ; This “Winter Rainfall Field Experiment”is essentially the second component of the “East Asian Monsoon Field Experiment –Participation of the MAHASRI (post-GAME) international field experiment”was originally proposed by Professor Tsing-Chang Chen. In order to follow the administrative requirement of the National Science Council, this project will be administrated by Professor Ming-Cheng Yen, but the essence and integrity of the East Asain Monsoon Experiment is maintained as origionally proposed. Heavy rainfall events caused by typhoons have been a major issue the government stresses. However, winter rainfall that affects the daily life of residence in northern Taiwan has not received much attention. Througout the cold season, northern and eastern Taiwan frequently undergoes consecutive rainy days and occationaly heavy rainfall. In late November 2007, a heavy rainfall event struct northeastern Taiwan and caused mudslides in numerous villages. This event reminds us that the impact of heavy rainfall cannot be neglected during winter. Through our pilot studies, Taiwan lows, a low pressure system developed over ocean northeast of Taiwan, play a key role in the northern Taiwan rainfall. Taiwan lows form over a shallow trough about 200 km off the northeast coast of Taiwan. This trough is also known as the Taiwan trough. When an East Asian cold surge erupts and passes through the Taiwan trough, it perturbs the Taiwan trough and often leads to a generation of low pressure disturbance. Such disturbances would later become Taiwan lows which produce rainfall over north-northwest Taiwan. The East Asian cold surge activity also creates cyclonic vortices over the western tropical Pacific. Such vortices, known as cold-surge vortices, propagate toward the west at a slow speed and are moisture-laden. They exert profound impact on Philippine and Vietnam during late fall, and on Malaysia and Indonesia during winter. Aiming to establish a comprehensive understanding of these winter weather systems, we planned a field experiment and began pilot studies of the East and Southeast Asian weather phenomena a few years ago. Through research, it was found that about three-quarters of winter rainfall in northern Taiwan is contributed to by Taiwan lows. The following scientific issues were also discovered but require further examination and confirmation: Rainfall classification –role of Taiwan lows; Formation mechanism and development of Taiwan lows; Multiple-scale interaction among winter weather systems. During the polot studies, we also noticed that the majority of Southeast Asian countries have little knowledge of cold-surge vortices and their physics. There is an urgent need for Taiwan to help these countries sovle these meteorological issues. In order to solve the aforemented questions, improve winter weather forecast, and assist in international meteolorigcal research, we propose the “Winter Raifnall Experiment” Research Project. The Winter Raifnall Experiment not only features substantial pilot research as its scientific keel, but has also established a bilateral collaboration with the Monsoon Asian Hydro-Atmosphere Scientific Research and Prediction Initiative (MAHASRI; led by Japan). Through this collaboration, the Witner Raifnall Experiment will be supported by severn countries (Japan, Vietnam, Malaysia, Indonesia, Thailand, Philippine, and the U.S.A) in terms of observing facilities and data exchange. Such collaboration ultimately expands the domain of experiment and the quantity of data, without further cost. A successful collaboration with the Southeast Asian countries through the Witner Raifnall Experiemnt will be very help for the diplomatic situation of Taiwan. ; 研究期間 9708 ~ 9807 |
