論台灣之梅雨
―台灣長期天氣預報問題研究之四―

On The “Plum Rains” in Taiwan 

王時鼎

S. T. Wang

Abstract

　　This paper presents a climtological and synoptic study of the Plum Rains (Bai-U) in Taiwan. The primary conclusions may be summarized as follows:
　　(1) The Plum-Rain regime in Taiwan can be identified clearly through the use of historical rainfall data. Its period spans from mid-May to mid-June. This regime has been found more evident in northern Taiwan than in southern Taiwan.
　　(2) The Plum Rains in the area begin about two weeks alter the rain season first appears in the Indo-China Peninsula, and ends at the time when Taiwan is under the influence of the subtropical ridge instead of the southwest monsoon system.
　　(3) There is a close relationship in the beginning of this rain season in Indo-China, South China and Taiwan, South Japan, and Central China. However, the durations, average rainfall Intensities, and prevailing circulation patterns for each region mentioned are quite different from one another.
　　(4) The maximum rainfall during the Taiwan Plum-Rain season has been generally found in the middle stage of the period, ie. Jate May or early June, and is associated with certarn definite synoptic patterns both at the surface and aloft.
　　(5) By using the 5-day mean temperature and pressure curves for Taipei, the characteristics of the Plum-Rain regme in Taiwan can be best described.