臺灣東部地區梅雨季降水與豪雨之氣候特徵

Climatological Characteristics of the Precipitation and Heavy Rainfall over Eastern Taiwan in Mei-yu Seasons

陳泰然(George Tai-Jen Chen) ； 王子軒(Tzy-Shyuan Wang) ； 黃心怡(Shin-Yi Huang)

《大氣科學》 41卷1期 (2013/06) Pp. 1-19

摘要

本文利用中央氣象局東部地區1997～2006年5－6月梅雨季高時空解析度之氣象站／自動雨量站觀測資料，探討Post-TAMEX 13-15預報分區，即宜蘭縣、花蓮縣及台東縣，與依地理位置／地形高度之自然分區之降雨強度、降雨機率、豪雨發生頻率之日夜變化，並探討豪雨發生頻率與降雨強度之時間和地形關連。結果顯示，不論各預報分區或自然分區，在5月、6月或5－6月梅雨季，降雨強度、降雨機率及豪雨發生頻率最大值皆出現在午後，顯示太陽輻射加熱驅動局部環流在激發午後對流發展扮演重要角色。梅雨季貫穿各高度之豪雨發生頻率最大主軸一個出現在午後1400－1600 LST，反映太陽輻射加熱驅動之局部環流在激發豪雨之關鍵角色；另一個在入夜1800－2000 LST，反映除局部環流與地形效應外，綜觀尺度強迫在東部地區梅雨季之豪雨產生亦扮演重要角色。此外，花東縱谷區午後降雨強度與其增強速率較花東山區與花東濱海區為大之現象，由過去研究結果顯示部分可能乃因濱海區之海風可跨越花東山脈進入縱谷區，且海風可由花東縱谷北側與南側入侵之故。

關鍵字

梅雨季 ； 降雨強度 ； 豪雨發生頻率 ； 午後對流 ； 太陽輻射加熱 ； 局部環流

並列摘要

Observational data with high spatial and temporal resolutions from the Central Weather Bureau meteorological stations and automatic rainfall stations in eastern Taiwan in May-June Mei-yu seasons in 1997~2006 were used to study the diurnal changes of the intensity and probability of precipitation, and the frequency of heavy rainfall occurrence. The relationship between the temporal and spatial distribution of the frequency of heavy rainfall occurrence and the intensity of precipitation were also investigated.The results showed that no matter for either subdivisions or natural regions, in May / June / May-June Mei-yu seasons, the maximums for the intensity and the probability of precipitation, and the frequency of heavy rainfall occurrence all appeared in the afternoon. It suggested that the solar radiation heating, which drove the local circulations, played an important role in activating the development of afternoon convection. There were two maximums in the axis of maximum frequency of heavy rainfall occurrence for overall heights. One appeared in the afternoon hours of 1400-1600 LST, reflecting that the solar radiation heating, which drove the local circulation, played an important role in triggering the heavy rainfall; while the other was in the evening hours of 1800-2000 LST, reflecting that besides local circulations and topographic effects, synoptic-scale forcing also played an important role in the occurrence of heavy rainfall in eastern Taiwan during Mei-yu season. Besides, the intensity of precipitation and its rate of increase in the afternoon hours in the region of Hua-Dong Vertical Valley were both larger than those in the regions of Hua-Dong mountain and Hua-Dong seaside. These features as suggested by the previous research results were perhaps partially due to the sea breeze of the seaside region could cross over the Hua-Dong mountain range into the Hua-Dong Vertical Valley and could also invade via the northern end and southern end.

並列關鍵字

Mei-yu season ； Intensity of precipitation ； Frequency of heavy rainfall occurrence ； Afternoon convection ； Solar radiation heating ； Local circulation