梅雨季台灣中北部地區豪（大）雨之氣候特徵研究

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

陳泰然(George T. J. Chen) ； 張子琦(T. C. Chang)

《大氣科學》 30卷2期 (2002/06) Pp. 171-185

摘要

Surface rainfall data over central and northern Taiwan in the period of May-June 1991-1996 were used to study the climatological characteristics of heavy rains in Mei-Yu season. Results showed that the spatial distribution and diurnal variation of average rainfall were strongly modulated by terrain effect and local circulation. This led to a NE-SW oriented axis of maximum rainfall along western side of Snow Mountain Range and Central Mountain Range during 1500-1800 LST. There was a remarkable maximum rainfall area above 140 meters, especially of 200-550 meters on the mountain slope during 1500-1700 LST. Also, there existed minor relative heavy rainfall area at an altitude of 140-200 meters during midnight (0100-0300 LST) and at 350-850 meters before noon (1000-1100 LST).
The high frequency of heavy rain occurred mainly located along the mountain slope area on southwest of Snow Mountain Range. It was differ from the previous study by Chen and Yang (1988) who observed high frequency over Hsin-Chu area along the northwestern coast. There was a NE-SW oriented axis of maximum frequency stretching form Chang-Hwa area to Big Snow Mountain. The axis was almost parallel to the southwestern flow in lower troposphere during Mei-Yu season and obviously modulated by terrain effect.
There was a notable diurnal variation of heavy rain frequency with a peak occurring at 1600 LST over both plain and mountain areas. The frequency of localized heavy rain events over mountain area was higher than over plain area most of the time during analyzed period. The frequency increase in the afternoon hours for types A+B (≥50mm/12h, but＜130mm/24h defined as type B) and A+B+C (≥50mm/24h, but＜130mm/24h defined as type C) was much more as compared to that for type A (≥130mm/24h). This tends to suggest the important role of solar heating over both mountain and plain areas for heavy rain occurrence, particularly for types B and C.

關鍵字

豪（大）雨 ； 空間分佈 ； 日夜變化 ； 局部環流 ； 地形效應

並列摘要

Surface rainfall data over central and northern Taiwan in the period of May-June 1991-1996 were used to study the climatological characteristics of heavy rains in Mei-Yu season. Results showed that the spatial distribution and diurnal variation of average rainfall were strongly modulated by terrain effect and local circulation. This led to a NE-SW oriented axis of maximum rainfall along western side of Snow Mountain Range and Central Mountain Range during 1500-1800 LST. There was a remarkable maximum rainfall area above 140 meters, especially of 200-550 meters on the mountain slope during 1500-1700 LST. Also, there existed minor relative heavy rainfall area at an altitude of 140-200 meters during midnight (0100-0300 LST) and at 350-850 meters before noon (1000-1100 LST).
The high frequency of heavy rain occurred mainly located along the mountain slope area on southwest of Snow Mountain Range. It was differ from the previous study by Chen and Yang (1988) who observed high frequency over Hsin-Chu area along the northwestern coast. There was a NE-SW oriented axis of maximum frequency stretching form Chang-Hwa area to Big Snow Mountain. The axis was almost parallel to the southwestern flow in lower troposphere during Mei-Yu season and obviously modulated by terrain effect.
There was a notable diurnal variation of heavy rain frequency with a peak occurring at 1600 LST over both plain and mountain areas. The frequency of localized heavy rain events over mountain area was higher than over plain area most of the time during analyzed period. The frequency increase in the afternoon hours for types A+B (≥50mm/12h, but＜130mm/24h defined as type B) and A+B+C (≥50mm/24h, but＜130mm/24h defined as type C) was much more as compared to that for type A (≥130mm/24h). This tends to suggest the important role of solar heating over both mountain and plain areas for heavy rain occurrence, particularly for types B and C.

並列關鍵字

Heavy rain ； Spatial distribution ； Diurnal variation ； Local circulation Terrain effect