通過台灣北部海上颱風與台灣中南部豪雨之研究

A Study on the Relationship between Heavy Rain over Southwestern Taiwan and Typhoon Passing over Seas North of Taiwan

俞家忠(Chia-Chung Yu)

《大氣科學》 9卷1期 (1982/05) Pp. 95-112

摘要

本專題係利用民國41－70年通過台灣北部海上之颱風（包括形成於台灣東部近海及其北部海上者）資料，地面及高空圖，探空觀測資料，以及台灣中南部（清泉崗、台中、嘉義、台南、岡山及屏東南場）六個測站之降水紀錄，以研究此區颱風對台灣中南部降水之關係，並以任何一個測站所測得日雨量等於或大於200公厘及任何一個測站所獲得總雨量達到等於或大於500公厘之降水強度為豪雨之定義，藉統計求出引起此種中南部地區豪雨之颱風共計18個，其中除形成於台灣東部近海及北部海上者3次外，另15次係自其他地區所移進。引起台灣中南部豪雨之颱風，均發生於6－9月份，其中尤以七八月份佔絕大多數，分別為7及5次。經研究顯示，此類颱風形成台灣中南部豪雨之主要原因，係颱風通過有關地區後，觸發來自低緯並通過南海而抵達台灣之潮濕不穩定氣流所造成。此種利於台灣中南部豪雨氣團之特性，經個案研究獲知，除水汽相當豐沛外，下對流層有較顯著之不穩定現象，自地面至上對流層間，伴有多次冷暖平流存在。此種豪雨之發生，與西南氣流有關，但其出現時機並非與台灣中南部發生較強之高空西南風相吻合，而係與低層噴射氣流軸左前方象限中強烈輻合區之到達有密切關係

並列摘要

This report was based on the data collected and concluded from the Typhoons Passing through the seas north of Taiwan in the Period from 1952 to 1981, Surface and upper charts, and detail rainfall records of six stations ( Chin-Chuan-Kung, Tai Chung, Chiayi, Tainan, Kung-Shan and Ping Tung ) ovre south-western Taiwan. With these information, the relationship between ”heavy rains over south western Taiwan” and ”typhoons passing over Seas North of Taiwan” had been studied scientifically, The ”heavy rains” is defined as ”any station which obtained the Precipitation of 200mm daily rainfall and over, and in the mean time any station Which recorded 500mm of total rainfall and over”. The records showed that there were 18 Typhoons Which Caused heavy rains in South Wester Taiwan. three of them were formed in the seas very close to Eastern and North Taiwan, and the rest 15 came from other areas . Most of these Typhoons occurred in the period from June through September, especially in July (7 times) and August (5 times. After the Typhoon Passing over the Related Areas and Steering Moist Unstable air Flows to Taiwan From low Latitudes and South China Sea Was The Main Reason of Causing Heavy Rains in South Western Taiwan. It is Found by Case Study That the air Mass Favorable to Heavy Rain was ldentified as Very Unstable in The Lower Troposphere and existing with many layers of cold advection and warm advection Between Surface and upper Troposphere. These heavy rains were although related with the south west flow. However, The triggering mechnism of occurrence was due to approaching of the intense Convergence zone associated with the left front quadrant of low level jet axis of south west flow.