梅雨季(5 月中~6 月中)過後，因為太平洋高壓脊深入台灣抑制擾動發展，雨量減少很多(Chen and Chen 2003)，但台灣西南部仍有豪雨發生(Chen et. al. 2007a)，主要降水來源為陣雨(Chen and Chen 2003)。檢視氣象局自動雨量站 (Chen et. al. 2007a) 在1997~2009 年的雨量資料發現1997、1999、2001、2005、 2008 及2009 等6 年在6 月下旬仍有豪雨發生(在此，豪雨的定義為至少有一雨量站的日雨量>130 mm 且有一時雨量大於15 mm， Wang et. al. 1985)。其中以2008 年6 月下旬共發生55 次豪雨，平均一天約有3 ~ 4 個雨量站偵測到豪雨為最多。豪雨的發生不但綜觀天氣存在有利的環境，地形效應亦扮演重要角色。在1997~2009 年6 月下旬台灣西南部的平均降雨極值除了在500 公尺地形等高線上，在平地亦有一降雨極值(22.5N、120.5E)，其強度與斜坡相當。地形效應如何影響平地的降雨極值，是一個值得研究的課題。本研究將收集2008 年6 月下旬ECMWF/TOGA 資料、氣象局的天氣、雷達、衛星及降水資料，再配合SoWMEX 資料及中尺度數值模式(WRF)，嘗試探討2008 年6 月下旬發生豪雨時的綜觀天氣、台灣西南部中尺度環流及地形效應在激發豪雨及維持豪雨所扮演的角色。 After the cessation of Mei-Yu season (mid-May to mid-June), rainfall over Taiwan declines significantly due to the advancement of the ridge of the western Pacific subtropical high into Taiwan and suppressing the development of disturbances (Chen and Chen 2003).Most of rainfall is contributed from showers. Nevertheless, heavy rainfall events are likely observed over southwestern Taiwan (Chen et al. 2007a). According to rainfall data from the Automatic Rainfall and Meteorological Telemetry System (ARMTS, Chen et al.2007a), heavy rainfall events occur in late June in 1997, 1999, 2001, 2005, 2008, and 2009. Heavy rainfall here is defined as a daily rainfall accumulation greater than 130 mm and an hourly rainfall rate exceeding 15 mm recorded at a minimum of one rainfall observation site (Wang et al, 1985). Among these years, there are 55 heavy rainfall occurrences in 2008. An average of nearly 4 occurrences takes place per day. The commencement of heavy rainfall is under a suitable large-scale environment. The orographic effects also play an important role. Over southwestern Taiwan, the maximum averaged rainfall in late June during 1997-2009 occurs over in sloped areas and low lands (near 22.5 °N and 120. 5 °E). How the orographic effects produce the rainfall maximum over low land is worthy of studing. In this study we will perform observational analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) data, satellite imagery, radar reflectivity, rainfall data, and data from SoWMEX for the synoptic and mesoscale processes to investigate the commencement and maintenance mechanisms of heavy rainfall events.The mesoscale process associated with the development of the heavy rainfall event and the orographic effects on the enhancement of accumulated rainfall are examined by a numerical model. 研究期間：9908 ~ 10007
