台灣地形對雨量之增減作用：濁水溪至高屏溪流域的降水分布－（上）個案分析

On the Topographic effects of Precipitation over Taiwan Rainfall Distribution of Southwest Taiwan-Part 1: Case Study

劉廣英(Koung-Ying Liu) ； 謝維權(Wei-Chyuan Shieh) ； 曲克恭(Ko-Kung Chu)

《大氣科學》 15卷1期 (1987/03) Pp. 89-102

摘要

地形對降水有很大的影響。根據作者等的研究獲知，此種影響不但及於降水發生的先後、雨量的大小與分布，且導致台灣地區一些半永久性的大雨中心。本研究即利用民國65至70（1976～1981）年台灣地區15次大雨個案中，濁水溪至高屏溪（本省西南部）地區有顯著雨量的個案進行分析，以瞭解區內地形對大雨分布的貢獻。研究中不但考量到大雨時的綜觀天氣圖型態及低層（850 mb）的風向風速，並選取了自西向東（甲線）及自西南向東北（乙線）兩條分析線。在該二線上均有高度不一（隨地形而變）的雨量站，由而可分析出氣流方向、地形高低與降雨起止時間、大小，以及降雨量分布的關係。而後並將各線上的歷次個案合併作合成分析，以找出地形與降水關係的重要特徵。分析結果顯示地形抬昇及合流作用，以及海陸摩擦作用的差異是形成降局部大雨及降水分布變化的地形因素。而該因素的大小變化與風向風速以及大氣的穩定度與含水量有關。平均而言，研究區內的歷次大雨，山區的累積雨量為平地累積雨量的5至9倍，最大可達68倍，值得我們注意。另外，甲線有部份個案在北港以及乙線有部份個案在阿蓮等平地地區，有第二（副）大雨中心。而在西南東北向袋形谷地底部之達邦，當850 mb吹西南強風時雨量特別多，亦為研究區內降水的特徵。以上分析結果將透過數值模擬做進一步的分析，以瞭解各因素貢獻的大小、作用的靈敏度、彼此間的關係。因篇幅的關係本文分為（上）檔案分析－對現象的描述及瞭解；（中）合成個案分析－包括降水分布、水汽狀況、穩定度以及平流作用，以瞭解大雨的主要特徵；（下）數值模擬－分析各項因素的貢獻。

並列摘要

The irregular topography on all scales influences atmospheric motions as well as precipitations through many ways. The nature of the atmospheric response, therefore, depends on the related topography and the characteristics of the atmosphere. In order to make a further study of the topographic contribution to the rainfall distribution 8 heavy rain events in southwest part of Taiwan are analyzed. For each event rainfall amount is analyzed along two (A & B) different lines with different direction and slope. After that composite analyses of each line are carried out. All the results of our work give good evidence to prove that mountain area would get more rain than its vicinity under suitable conditions. The rainfall amount of the mountain area in the considered region is, in the mean, about 5 to 9 times greater than that of the plane area. A secondary center of heavy precipitation along the coast of line A and very prounounced rainfall amount occured in the SW ➝ NE valley under the influence of southwest flow are another two evidences that topography is a very important factor of precipitation and its distribution.This paper is divided into three parts: Part 1 case study; Part 2 composite case study and Part 3 numerical simulation. All this work will provide a good result of the considered problem.