梅雨季中尺度對流系統與台灣北部地區降雨相關性之研究

The Relationship of Mesoscale Convective Systems and Precipitation over Northern Taiwan in Meiyu Season

陳泰然(George T. J. Chen) ； 黃文亭(W. T. Huang) ； 王尹懋(Mark Y. M. Wang)

《大氣科學》 29卷1期 (2001/03) Pp. 21-36

摘要

本文利用中正機場都卜勒雷達所觀測到的1988～1993年5～6月梅雨季台灣北部地區的中尺度對流系統，分析其與降雨的關係。首先將中尺度對流系統分爲線狀對流系統與非線狀對流系統，再將線狀對流系統依形成型態、層狀降水區所在位置、系統主軸走向等做不同的分類。分析不同類型之中尺度對流系統在台灣北部地區之降雨量，幷探討梅雨季裏不同時段降雨量與中尺度對流系統的關係。
結果發現，中尺度對流系統是導致台灣北部梅雨季降雨的主要因子，占梅雨季總降雨量63%，唯系統實際降雨量在各測站間具有很大的差異。雖然非線狀對流系統發生頻率遠多於線狀對流系統，但是平均而言，線狀對流系統的降雨量比非線狀對流系統者爲多。以線狀對流系統的形成型態而言，後造型的降雨量最多，破線型次之；以層狀降水區位置而言，主軸型的降雨量遠多於其他類型；以系統主軸走向而言，東西走向的降雨量最多，東北－西南走向次之。這些不同類型線狀對流系統所造成降雨量多寡，實與環境低對流層垂直風切息息相關，垂直風切大者系統平均降雨量亦大。

關鍵字

梅雨季 ； 中尺度對流系統 ； 線狀對流系統 ； 非線狀對流系統

並列摘要

Mesoscale convective systems (MCSs) observed by Doppler radar at the CKS International Airport during the Meiyu season of 1988～1993 were analyzed to investigate their relation with the precipitation in northern Taiwan. The MCSs were first classified into line and non-line types. Line-type MCSs were further categorized according to different types of formation, stratiform region, and axis orientation. Precipitation for different types of MCSs in northern Taiwan was analyzed and the relation of MCSs and precipitation indifferent time period in the Meiyu season were also investigated.
Results showed that MCSs were the major contributor to the precipitation of Meiyu season in northern Taiwan. It contributed 63 percent of total precipitation in Meiyu season, although there were remarkable differences in precipitation among stations. Line-type MCSs occurred less frequently than non-line type ones, however the former contributed more precipitation on average. Back-building type produced most precipitation followed by broken-line type among all formation-type MCSs. Parallel-type MCSs produced much more precipitation than others in all stratiform region types. East-west type produced most precipitation followed by NE-SW type in all orientation-type MCSs. Different types of mesoscale line convection produced different precipitation amount which was highly related to the low-level vertical winds hear of the environment. MCSs developed with a large vertical wind shear also produced large amount of precipitation.

並列關鍵字

Meiyu season ； Mesoscale convective system ； Line-type mesoscale convective system ； Non-line type mesoscale convective system