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梅雨季台灣中北部地區伴隨鋒面與中尺度低壓豪(大)雨與定量隆水之中尺度氣候研究

A Study on the Mesoscale Climatology of Heavy Rainfall and Quantitative Precipitation Relevant to Fronts and Mesolows over Northern to Central Taiwan in Mei-Yu Season

Abstracts


本文以中尺度氣候觀點,利用1991至1996年5-6月梅雨季台灣中北部(24°N以北)地區地面降水資料,分析42個梅雨鋒面個案與10個台灣西北沿海地區中尺度低壓個案,在中央/雪山山脈西側之台北縣市至彰化縣(即Post-TAMEX預報實驗分區1-6)於鋒面過境與低壓旋生前後逐時各型豪(大)雨出現頻率、降雨機率及降雨強度之氣候特徵。 結果顯示,各分區豪(大)雨均與鋒面密切關連,發生頻率在鋒前數小時開始增加,並在鋒面通過後1-2小時內達最大。台灣北部主要產生B型豪雨;愈向中部則A型豪雨比例漸增。鋒面過境前後之降雨機率與降雨強度變化亦顯示,各區最大降雨機率與降雨强度幾皆發生於鋒面過境至之後3小時之間,平均強度則以新竹、台中最高(分區4、5),應為較佳之地形舉升條件所致。此外,鋒前系統於中部地區之降水亦有較大貢獻,北部地區則降雨亦能在鋒後持續出現。 台灣西北沿海地區中尺度低壓之旋生,對於旋生區內與其南側之降水均有明顯助益,且以旋生區南側效果較大(分區4與5)。降雨強度於旋生時開始增加,主要影響時段約在旋生後的6小時內,並約於3小時後達最大,之後減弱。降雨機率在中尺度低壓旋生前後,則可上升約40%或更高。因低壓旋生而導致豪大雨頻率之增加,則以分區4與5較明顯,其他分區則影響有限,且形成者多屬B型豪雨,而少有A型豪雨或大雨,此亦與低壓主要影響時段僅數小時之結果一致。

Parallel abstracts


From a mesoscale climatology viewpoint, the present study utilized precipitation data from surface rain-gauge network north of 24°N during Mei-Yu seasons (May-June) from 1991 to 1996, and analyzed the characteristics of rainfall over northern to central Taiwan (forecast areas 1-6 in the Post-TAMEX experiment) in relation to frontal passages and mesolow cyclogenetic events over northwestern Taiwan. During 6 Mei-Yu seasons, a total of 42 Mei-Yu front and 10 mesolow cases took place, and the frequency of heavy-rain events, precipitation probability, and precipitation intensity were obtained and their evolution investigated. Results show that heavy rainfalls are closely linked to Mei-Yu fronts. Their frequencies start to increase several hours before frontal passage, and reach the peak only 1-2 h after the passage. The majority of heavy-rain events are of B-type in northern Taiwan, while the percentage of A-type increased gradually toward central Taiwan. Both precipitation probability and intensity reach maximum within 3 h after frontal passage in all areas, and the strongest precipitation intensity appeared in areas 4 and 5 (Hsinchu and Taichung), most likely due to a steeper terrain. In addition, a higher fraction of total rainfall is consisted by pre-frontal systems in areas 4 and 5,while precipitation can last for many hours after frontal passages in area 1(Taipei and Keelung). Mesolow cyclogenesis in northwestern Taiwan is also helpful in increasing precipitation near the region of cyclogenesis, and even more so to its south (areas 4 and 5). Precipitation intensity starts to increase at the time of cyclogenesis, and reaches the maximum about 3 h later before decreasing, so that the period significantly affected by mesolows is only about 6 h. The difference in precipitation probability before and after mesolow cyclogenesis can reach 40% or more. The increase in heavy-rainfall frequency, however, is more evident only in areas 4 and 5, with the majority being type-B events.

Cited by


龔楚媖(2010)。氣候概念模式於梅雨定量降雨預報之評估與分析〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2010.02106
陳姿瑾(2009)。西南氣流實驗之雨滴譜分析研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2009.02914
姜禮鴻(2005)。花蓮地區梅雨季降水特性與豪(大)雨個案診斷分析〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2005.02696

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