梅雨季台灣中南部地區豪大雨之氣候特徵研究

On the Climatological Characteristics of Heavy Rain Events over Central and Southern Taiwan in Mei-Yu Season

陳泰然(George Tai-Jen Chen) ； 林宗嵩(Tsung-Sung Lin)

《大氣科學》 25卷3期 (1997/09) Pp. 289-306

摘要

本文利用1987~1995年5~6月中南部地區地面雨量資料，分析豪大雨空間分布、日夜變化以及平地與山區的差異，並分析1991~1995年5~6月中南部與其各分區相對於梅雨鋒的豪大雨時空分布特徵，以及各分區相對於中尺度旋生的豪大雨時間分布。結果發現，地形顯著影響豪大雨的空間分布，致使最大頻率主軸在台南與阿里山之間，約沿阿里山山脈與玉山山脈呈西南～東北走向。豪大雨發生頻率有顯著日夜變化，5~6月1600LST之最大值極為顯著，顯示太陽加熱之重要性。5月與6月以及平地與山區的日夜分布，亦有顯著的差異，特別是5月正午前後時段最小值轉為6月之最大值更為有趣，顯示在梅雨季後期局部環境條件與局部強迫作用在導致豪大雨之重要角色。此外，亦發現梅雨鋒與中尺度低壓在各分區豪大雨的發生均扮演重要角色，鋒前頻率較鋒後為高，旋生後較旋生前為高。

關鍵字

豪雨 ； 梅雨鋒 ； 中尺度低壓 ； 日夜變化 ； 地形效應

並列摘要

Rainfall data over central and southern Taiwan in the period of May-June 1987-1995 were used to study the spatial distribution and diurnal variation of heavy rains as well as the differences over plain and mountain areas. Data in the period of May-June 1991-1995 were also used to study the spatial and temporal distribution of heavy rains with respect to the Mei-Yu front as well as the temporal variation of heavy rains with respect to the mesolow formation over the whole region and each subregion.Results showed that the spatial distribution of heavy rains was strongly modulated by the terrain effect. This led to a NE-SW oriented axis of high frequency between Tainan and Alishan along the Alishan and Yushan mountain ranges. There was a significant diurnal variation of heavy rain frequency with a peak occurring at 1600 LST. This tends to suggest the importance of solar heating. A remarkable difference in diurnal variation was also observed between May and June as well as between the plain and mountain areas. It is interesting to note that a minimum frequency near noon time in May increased to a maximum in June. This suggests that the local environmental conditions and local forcings became more important in producing heavy rains in the later period of Mei-Yu season. In addition, Mei-Yu front and mesolow were found to play important roles in the occurrence of heavy rain in each subregion. Heavy rain occurred more frequently ahead than behind the front and after than before the mesolow formation.

並列關鍵字

Heavy rain ； Mei-Yu front ； Mesolow ； Diurnal variation ； Terrain effect