臺灣地區乾旱問題之分析

林棽(Shen Lin)

指導教授 ： 林沛練 ； 劉紹臣

國立中央大學/地球科學學院/大氣物理研究所/碩士(2015年)

摘要

本研究使用中央氣象局15個測站的1961-2011年日降水資料和National Climatic Data Center全球地表異常溫度月資料進行分析。全球暖化造成地球表面水汽蒸發量增加，大氣水汽飽和程度增加，以及大氣穩定度增強，進而對降水造成影響。使用inter-annual方法定量分析臺灣地區降水的變化情況發現:極端大雨之降水量增加113.19 % K^(-1)，極端小雨之降水量減少 60.66 % K^(-1)。而小雨降水的減少就會對乾旱問題造成影響。
本研究分別對臺灣各區域的乾日日數變化、連續不降水日數變化，即乾旱強度變化，和標準降水指數（SPI）變化與溫度變化的關係進行定量分析。臺灣地區全年的乾日日數增加16.42 % K^(-1)。同時，我們根據月平均降水的分佈形態將臺灣分為北部、西南部和東部三個區域。在乾旱問題特別受到關注的乾季，也就是每年11月至第二年4月的分析中，各個區域的乾日日數均有顯著的上升趨勢。此外，連續乾日日數也隨溫度升高有所增加，特別在連續15日以上不降水的部分，北部區域增加約 12天 K^(-1)，西南部區域增加 52天 K^(-1)，東部區域增加約 11天 K^(-1)。在 SPI 的分析中，隨溫度升高，北部和東部乾季每次發生乾旱的強度均有增強的趨勢。而西南部區域因強降水雨量的增加使得該區域的降水量出現增加的狀況。不過，小雨的減少卻令西南部區域的連續乾日日數增加最為明顯，出現明顯乾化的情況。

關鍵字

乾旱 ； Inter-annual方法 ； SPI

並列摘要

Using daily precipitation data of 15 stations from Central Weather Bureau and global mean temperature from National Climate Data Center covering the period of 1961-2011, we find the changes of drought over Taiwan under the condition of the global warming by inter-annual method. Global warming leads to the increase in temperature which attributes to the water vapor availability, water-holding capacity in the atmosphere and the atmospheric stratification. Based on the temporal distribution of precipitation, and the inter-annual method to do the qualitative and quantitative analysis, we find that extreme heavy rainfall increases 113.19 % K^(-1), while extreme light rainfall decreases 60.66 % K^(-1). The results also imply the number of dry day is increasing under global warming.
In this research, we describe the change of drought over Taiwan according to the number of dry day, the number of consecutive dry day and the standardized precipitation index (SPI). The number of dry day increases 16.42 % for each degree Kelvin. Meanwhile, we discuss drought in northern, western and eastern areas by considering the prevailing winds in different seasons and topography. We also focus on drought in dry season starting from November 1st to the following April 30th. The results illustrate that both the number of dry day and consecutive dry day increase when temperature increase. Especially for the number of greater than 15 consecutive dry days. This number increases 52 days K^(-1) in western area while it increases about 12 days K^(-1) in northern area and 11 days K^(-1) in eastern area. Moreover, there is an increasing trend in the intensity of drought in dry season under global warming in northern and eastern areas. However, because of the increase of the heavy rainfall in western area, the quantitative analysis of SPI shows an increasing trend of the total precipitation in dry season.

參考文獻

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