• 作者： 林民生; 趙世騰
• 作者服務機構： 中央氣象局預報中心
• 中文摘要： 利用累積雨量及累積雨日比值法，經挑選 1963, 64, 76, 77 年為乾旱個例年，1967, 73, 74,75 年為正常個例年，據以比較其差異性。另依天氣圖分類降雨型，發現臺灣低壓、滯留鋒、鋒面及颮線型降雨為主要構成臺灣地區 2 至 4 月之成雨系統，這些綜觀輻度系統在乾旱年其出現頻率減少40%以上，且各降雨型平均降雨強度減弱達30%以上，尤其中南部地區其減弱更為明顯。從距平合成圖解析乾旱之形成，發現 2 月份亞洲大陸高壓於乾旱年普遍增強，但高空西方槽減弱，形成150°E以東主槽之乾寒潮型居多，或常伴有移動性高壓系統自華中至華南一帶出海。3、4月間由於副熱帶高壓提早發展西伸，臺灣附近一帶氣壓、高度偏高，迫使鋒面帶北退及不明顯化，造成雨量銳減，以蔚成春季乾旱。
• 英文摘要： By means of the accumulated rainfall andrain-day ratio method during the Feb. to April,we select 1963, 64, 76, 77 as drought cases, andchose 1967, 73, 74, 75 as normal cases. Springrainfall of drought and normal cases have beenstudied in detail to reveal the pertinent featurein synoptic climatology for the drought. According to rain-type classification, we findthat Taiwan low, Stationary front, Frontalsystem and Squall line types are the dominantcauses for spring rainfall. During the droughtcase, the occurrence frequency of these weathersystems decrease over 40%, and rainfall intensitydeficit is over 30%, especially in central andsouthern Taiwan are most pronounced. We conclude by aid of surface and 500 mbcomposite charts the strong Asia high pressureassociated with a weak continental troughfollowing by a migratory high pressure systemin southern China combined exhibit a dry out-break and companied the fine weather in Feb.during drought case. The extreme developmentand westward expansion over the Pacific highpressure in March and April force the conven-tional frontal zone to withdraw northward andweaking which provide a deficit in precipitationduring the spring drought.
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