臺灣地區梅雨前之乾旱研究

A Study of Drought over Taiwan Area, before Baiu Season

林民生(Ming-Sen Lin) ； 陳進文(Chin-Wen Chen)

《大氣科學》 6卷1期 (1979/05) Pp. 17-28

摘要

臺灣地區1977年2月起各地降雨日及降雨量銳減，分析降雨日距平百分率發現2月中部地區達－50%以上，愈往南部降雨日愈少，至3月高雄達－100%之極限，4月中南部地區亦在－80克以上。雨量距平百分率2月起中部達－75%以上，愈往南部降雨愈少，至3月高雄達－100 %之極限。2月至4月中南部地區乾旱嚴重，北部及東部地區則較緩和。分析乾旱之形成，推論乃由於臺灣東方廣大洋面持續海水增溫與水溫正距平帶北移，造成太平洋副熱帶高壓極端發展與西伸，使臺灣附近地區地面氣壓興高空各層高度普遍均呈正距平，既抑制臺灣低壓之發展，並造成鋒面系統偏北互不明顯化。加以亞洲地區高壓源地偏西，高壓路徑偏南，當其行經乾燥黃土高原，抵達臺灣上空之空氣較為乾燥。高壓帶籠罩下強烈下沉增溫使水汽含量銳減，形成700至500 mb 間穩定空氣層，成雲致雨機會稀少，直至梅雨開始始解消春季之長期乾旱。

並列摘要

The severe drought over central and southern. Taiwan area from February to April 1971 is identified by deficient in rain days and precipitation. The rain day deficiency reached -50% in Feb. for central Taiwan and increased to -100% in March for southern Taiwan. and the precipitation deficiency ranged from -75% to -100% during this period for most of the central and southern part of Taiwan.The initiation and maintenance of the drought are due to the persistence of warming sea surface temperature over the western Pacific high pressure region to an extreme development and westward expansion, The positive anomalies of pressure and height in Taiwan area and its vicinity supress the development of a Taiwan low and also force the frontal system to high pass northward. The origin of the high pressure center moves westward which causes the track of high pressure to pass through the arid area, of central China.The strong subsident warming of the dominant high pressure system during the drought season maintains a stable layer at 700-500 mb which decreases the condensation and rainfall until the onset of Baiu season in mid-May.