The Analysis of Climatological Characteristics of Non-typhoon Rainfall in Taiwan

台灣地區主要之降雨類型可大致分為颱風雨以及季風雨兩種，其中每年由颱風所帶來之降雨總量，會隨著颱風實際侵台數目而有所變化。本研究主要針對「非颱風降雨」進行深入討論，期望能由大環境氣壓高度場的變化對應至台灣周圍風場的改變，然後再由風場變異連結至台灣降雨型態的轉變，分析三者之間變異的關聯性。 本研究為使用1980年~2004年期間全台灣85個測站之日雨量觀測紀錄、台灣周圍(117.5°-125°E、20°-27.5°N)之850百帕風場資料，以及90°-170°E、0°-60°N範圍內之850百帕高度場資料以進行研究。本研究之研究方法主要分四部份：一、分離颱風雨，二、主成份分析，三、累計距平分析四、關聯性：找出「多雨」或「少雨」當時段之高度場、風場及海氣與非颱風降雨氣候值與距平值，並分析三者之間關聯性。 結果顯示：一、台灣地區每年之算術平均降雨量約為2400mm，而颱風降雨 的部分約平均佔23%，最多為38%(2004)，而最低僅佔了3%(1983)，年際變異很大。因此在分析降雨量之長期特性時，應將兩種類型之降雨分開探討。二、「非颱風雨」的三個主成份顯示：第一主成份台灣地區全為正值(或全負)，代表全台之降雨量為同升或是同降，其中以西南部的值較大；第二主成份主要是台灣之東北-西南為反相(out-of-phase)的型態；第三主成份則呈現了台灣東-西部為反相的型態。三、從「多雨」或「少雨」時段可看出風場、壓力與非颱風降雨有相當的關聯性，例如：在「少雨」時段，台灣地區之高度場多為正距平(positive anomaly)，風場多為輻散狀態，在「多雨」時段，台灣地區之高度場多為正負距平較小區域，風場距平多為西南風，與聖嬰亦存在關聯性。The main rainfall type of Taiwan can be divided into a typhoon rain and monsoon rain. The overall rainfall that typhoon brings yearly depends on the actual times of invasion. This research mainly discussed the ' non-typhoon rainfall ' , and expected to analyze the relation among the variations of the change of geopotential height in the entire environment, the corresponding change of airflow surrounding Taiwan, and the transition of rainfall type of Taiwan caused by he variation of airflow. We use the 85 stations of daily rainfall observation in Taiwan, the data of 850 hpa airflow surrounding Taiwan (117.5°-125°E、20°-27.5°N), and the data of 850 hpa geopotential height within this area (90°-170°E、0°-60°N) from 1980 to 2004 in this research. Four methods are used in this research. First, we extracted the typhoon rainfall. Second, the Principle Components Analysis. Third, the analysis of cumulation anomaly. Finally, we tried to find the relation among three climatology and anomalies, the geopotential height, the airflow and the rainfall of the duration of moist-rain or drought. This research reveals three important results. First, the yearly arithmetic mean of rainfall in Taiwan is about 2400mm. The typhoon rainfall accounts for around 23 %, 38% at most (in 2004) and 3 % at least (1983). This means a huge variation over years. Consequently, when analyzing the long-term characteristics of rainfall, it is suggested to discuss these two types separately. Second, three principle components of rainfall are derived by using the principle components analysis. The first one displays a positive coefficient in Taiwan, especially in South-east. The second one is a positive coefficient in North-west with a negative value in South-east, and the third is a positive value in West with a negative value in East. Finally, there is a considerately good relation between geopotential height and rainfall from the duration of moist-rain or drought, e.g., the geopotential height varies with the positive coefficients of different principle components to show a positive anomaly during the drought. This research has explored the relation among geopotential height, airflow in the entire environment and rainfall. In the future, we expect to use this index as an estimation criteria of yearly or seasonal change of non-typhoon rainfall in Taiwan after development and examination.摘 要 II ABSTRACT III 目 錄 IV 圖目錄 VI 表目錄 XIII 第1章、 緒論 1 1-1 研究動機與目標 1 1-2 文獻回顧 3 1-3 研究方法概述 6 1-4 論文結構 8 1-5 雨量資料與前處理 8 1-5-1、 雨量資料 8 1-5-2、 颱風雨分離 14 第2章、 篩選異常降雨時段 19 2-1 篩選方法 19 2-2 過程與結果 23 2-2-1、 主成份分析 23 2-2-2、 調和分析 29 2-2-3、 累計距平分析 52 2-3 相關研究整理 60 第3章、 特殊降雨時段海氣環境分析 62 3-1 環境場資料與處理 63 3-1-1、 環境場資料 63 3-1-2、 環境場資料處理 66 3-2 多雨事件分析 72 3-2-1、 1982(62-Pentad)~1983(19-Pentad) 72 3-2-2、 1991(66-Pentad)~1992(17-Pentad) 87 3-2-3、 1998(1~16-Pentad) 96 3-2-4、 綜合說明 101 3-3 少雨事件分析 103 3-3-1、 1999(3~22-Pentad) 103 3-3-2、 2001(72-Pentad)~2002(27-Pentad) 112 3-3-3、 2003(4~16-Pentad) 119 3-3-4、 綜合說明 123 第4章、 結論與建議 125 4-1 結論 125 4-2 建議 129 參考文獻 130 附錄A 研究方法 A-1 附錄B 特殊降雨事件氣壓高度場與風場距平 B-