台灣長期皿蒸發量趨勢分析及蒸發互補關係初探

Long-term Pan Evaporation Trend and Preliminary Investigation of Evaporation Complementarity in Taiwan

陳憲宗(Shien-Tsung Chen) ； 李奕欣(Yi-Hsin Li)

《農業工程學報》 62卷1期 (2016/03) Pp. 12-28

https://doi.org/10.29974/JTAE.201603_62(1).0002

摘要

隨著全球暖化，蒸發量預期會隨溫度上升而增加，但全球許多區域的皿蒸發量卻呈現下降的趨勢。台灣近二十年的短期皿蒸發量亦有下降趨勢，然因蒸發觀測儀器的更換，以致缺少具一致性的長期蒸發資料可供分析長期蒸發趨勢。本研究收集中央氣象局超過百年的長期蒸發及氣象觀測資料，分析早期20公分蒸發皿與當代A型蒸發皿觀測資料的統計特性，以及蒸發量與氣象因子的相關性。本研究採用支撐向量機發展蒸發資料重建模式，以20公分皿蒸發資料及具最高相關性的氣溫作為輸入變量，轉換為早期的A型皿蒸發重建資料，得到具一致性的長期皿蒸發資料；並利用Mann-Whitney-Pettitt改變點檢測法分析台灣長期皿蒸發量的趨勢，得知台北、台中、宜蘭、花蓮和高雄的皿蒸發趨勢為增加，嘉義、台南、恆春、台東的皿蒸發趨勢為下降；整體而言，除高雄外，長期皿蒸發趨勢有北增南減的現象。本研究初步探索蒸發互補理論，發現台灣的皿蒸發資料有呈現蒸發互補關係的跡象，但有待後續研究進一步釐清與探討。

關鍵字

皿蒸發量 ； 趨勢分析 ； 蒸發互補理論

並列摘要

Under global warming, the evaporation is expected to increase as the temperature increases. However, pan evaporation data over the past 50 years show a decreasing trend in many places. This has recently been discussed, and is termed the ＂pan evaporation paradox.＂ Pan observations during recent two decades in Taiwan also exhibit a decreasing trend. Although long-term pan evaporation data are available and the recording periods of some stations are more than 100 years, no long-term trend analysis of pan evaporation data has been studied in Taiwan. This is because that long-term pan evaporation data in Taiwan are not homogeneous in data properties. This inhomogeneity in long-term data is due to the use of different evaporation pans in the early time (20-cm pan) and the modern time (Class A pan). The observations from the 20-cm pan are usually greater than those from the Class A pan in the magnitude of as large as 50 mm/month in Taiwan. This study developed a data reconstruction model by using support vector machines to homogenize the long-term evaporation data from the two evaporation pans. Mann-Whitney-Pettitt method was used to detect the trend of long-term pan evaporation data. Analytical results reveal that, except for one station, the long-term pan evaporation trend in Taiwan exhibits an increasing trend in the north and a decreasing trend in the south. Preliminary analysis of the evaporation complementary relationship in Taiwan was also discussion. Using the precipitation as a variable to explain the environmental wetness, the evaporation complementary relationship can be demonstrated in Taiwan.

並列關鍵字

Pan evaporation ； Trend analysis ； Complementary relationship