台灣位於東亞大陸下風處，冬季時東北季風可將亞洲大陸的污染物傳輸至台灣，且台灣四面環海，受海洋影響顯著，由於風的吹拂，空氣中存在含海鹽氣膠，最後空氣中的氣膠和污染物再經由降雨沉降至地表，影響雨水酸鹼值和環境生態。因此利用台灣長期酸雨監測資料來了解降水化學的長期變化，以及和氣候的相關性。 本研究使用彭佳嶼、台北、宜蘭、中壢、新屋和成功2005 - 2013年降水化學資料。彭佳嶼、新屋和成功為背景測站，以海洋的貢獻為主，且彭佳嶼和成功nss-SO42−/Na+比值低於1，雨水中Na+比例最高。台北、宜蘭和中壢nss-SO42-濃度的變動程度在冬季較為顯著，有季節性分佈，且6個測站nss-SO42-/NO3-比值皆大於1，表示長程傳輸的重要性。 傳輸效應取決於東北季風的強弱，本研究中各測站Na+濃度高值大多發生在東北風增強的年份，反之Na+濃度低值多發生在東北風較弱的年份，且海溫是決定東北季風強弱的因素之一。結果發現Na+濃度變化和Niño 3.4海表面溫度(Sea Surface Temperature，SST)的相關性呈現反相位，顯示降水化學會間接受到海溫影響。 為進一步探討東北季風造成的影響，只選取東北季風型態及秋冬鋒面型態的降雨資料，結果顯示因為新屋與海距離較近，易受到傳輸而來的污染物影響，nss-SO42-濃度變動幅度比中壢大，成功nss-SO42-濃度變動小，且位於台灣東部，東北季風造成的效應沒有北部地區直接。 使用彭佳嶼在東北季風型態下Na+濃度極端值的風場，了解Na+濃度極大值發生時，事件日3天的風速大於平均風場，環流多為大陸高壓未出海時，高壓強度強、風速大，反之，Na+濃度極小值發生時，事件當日風速比平均風場小。 ;Taiwan is located to the southeast of the East Asian continent. In winter, the northeast monsoon can transport air pollutants from East Asian continent to Taiwan. Taiwan is surrounded by ocean; the effect of ocean is remarkable. Since the wind blowing, the sea-salt containing aerosols exist in atmosphere, and finally aerosols and pollutants deposit on ground via precipitation. The purpose of this study is to understand the long-term trends of precipitation chemistry and its correlation with regional climate pattern. This study analyzes the rain water data collected from 2005 to 2013 at Taiwan acid rain monitoring sites. Pengjia Islet, Hsinwu and Chenggong are background stations, where the main source is ocean. The ratio of nss-SO42-/Na+ is lower than 1 at Pengjia Islet and Chenggong. In winter, the variability and seasonality in nss-SO42- is noticeable at Taipei, Yilan and Chungli. The ratio of nss-SO42-/NO3- is more than 1 at 6 stations which presents the relative importance of long-range transport. The effect of transport depends on the strength of northeast monsoon, so higher Na+ concentration appears when northeast monsoon become stronger, while sea surface temperature (SST) is one of the factors determining the strength of northeast monsoon. It was found that the correlation between Na+ concentration and Niño 3.4 region SST is opposite in phase which indicates precipitation chemistry is indirectly affected by SST. In order to further investigate the impact caused by northeast monsoon on precipitation chemistry, we choose the rain water data associated with the weather types NE (northeast monsoon) and FA (winter front). It shows that Hsinwu is close to sea so it is easy to affect by long-range transported pollution and the variability in nss-SO42- at Hsinwu is higher than Chungli. The variability in nss-SO42- at Chenggong is lower because Chenggong is not affected by northeast monsoon so significantly. We analyzed the wind field and found extreme Na+ concentrations appear under the type NE at Pengjia Islet. The Na+ concentration maximum occurs when the wind speed over three days is larger than average. Meanwhile, the continental cold High still remains in continent so its intensity and wind speed are strong.
