本文首先定義台灣北部地區入梅、出梅之日期,並求得台灣北部地區近十年之平均梅雨期為5月17日至6月20日共35天;另採用圖解合成法分析1968~1977年梅雨期間亞洲地區之天氣型式及梅雨鋒面系統之降水特性,發現影響台灣北部地區梅雨期間降水多寡的主要天氣系統為東海高壓、西太平洋副熱帶高壓脊線及華南沿岸附近之中尺度低壓的相對位置及強度。
In this paper, we first define the onset and the end of the Mei-Yu season in northern Taiwan area, and find that the average Mei-Yu period is 35 days from 17 May to 20 June. Ten-years data (1968~1977) of Mei-Yu season in northern Taiwan area were analyzed to study the relationship between the precipitation and the synoptic patterns. We find that the rainfall intensity of Mei-Yu is mainly controlled by the positions and intensity of the East-China Sea high pressure, the ridge of the Western Pacific subtropical high pressure and the mesoscal low in the vicinity of the coast of South China.