Climate change in Sri Lanka: myth or reality? Evidence from long-term meteorological data
Climate change in Sri Lanka: myth or reality? Evidence from long-term meteorological data
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斯里兰卡的气候变化：神话还是现实？
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发表时间：
2008
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通讯作者：
Wajm de Costa
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作者：
Wajm de Costa
气候变化是当前全球论坛上讨论最多的问题之一。本文的目的是通过分析斯里兰卡主要气候带的七个选定地点(即阿努拉达普拉、库鲁内加拉、康迪、拉特纳普拉、巴杜拉、努瓦拉·埃利亚和科伦坡)的长期(即1869-2007年)月平均气温和降雨量数据，寻找斯里兰卡气候变化的证据。除康迪外，所有选定地点的十年平均气温都显示出极显著的(p<；0.001)在整个140年期间呈线性增长趋势。在包括康提在内的所有地区，在过去的6-10年里，几乎连续发生了年代际变暖。在1906年至2005年期间，除Ratnapura外，所有地区的持续变暖速度都大大超过了全球平均水平(即0.074摄氏度十年-1)。对年平均气温频率分布的分析表明，上述上升是因为整个气温分布随时间的变化，而不是由于几个极端温暖的年份。在所研究的七个地点中，有四个(即阿努拉达普拉、康迪、巴杜拉和努瓦拉·埃利亚)在整个140年期间显示出显著的十年平均年降雨量(RFA)随时间的线性下降趋势。努瓦拉·埃利亚的降雨率最高，为52毫米十年-1。在140年期间的各个趋势中，除科伦坡外，所有地点的十年平均RFA都有显著(p<；0.05)下降的时期。特别是，自1970年代以来，库鲁内加拉的降雨量减少了121毫米。自20世纪40年代和20年代以来，康迪和努瓦拉·埃利亚的降雨量分别在-67毫米十年-1的范围内下降。在所有地点，1990年至2007年期间的平均RFA低于1950-1989年期间的降雨量。降雨量的减少幅度从拉特纳普拉的28毫米年-1到库鲁内加拉的202毫米年-1不等。对降雨分布变化的分析表明，降雨量极低和降雨量高的年份的降雨量减少对连续几个时期的平均降雨量的贡献相对较大，而不是平均降雨量年的降雨量减少。在所有地点，RFA显示出不同强度的减少趋势，随着年平均温度Ta的增加，Nuwara Eliya的降雨率最高(371 mm OC-1)。对1950-1989年的月和年降雨量数据的分析表明，厄尔尼诺现象在接下来的一年里所有地点的RFA都减少了，主要是因为6-7月(西南季风)和1-2月的降雨量减少。从1990年起，除科伦坡和拉特纳普拉以外，厄尔尼诺事件后所有地区的RFA减少量都有所增加，这两个地区的降雨量都高于正常年份。值得注意的是，自1990年以来，所有地区都没有厄尔尼诺事件后6-7月降雨量的减少，因为1月、2月和10月-12月(东北季风)降雨量减少。
Climate change is one of the most-discussed issues in current global fora. The objective of this paper is to seek evidence for climate change in Sri Lanka by analyzing long-term (i.e. from 1869 to 2007) monthly data of air temperature and rainfall from seven selected locations (i.e. Anuradhapura, Kurunegala, Kandy, Ratnapura, Badulla, Nuwara Eliya and Colombo) representing the major climatic zones of the country. Decadal mean air temperatures of all selected locations, except Kandy, showed highly significant (p<0.001) linear increasing trends over the entire 140-year period considered. In all locations, including Kandy, almost continuous decadal warming has occurred during the last 6-10 decades. The rates of continuous warming in all locations except Ratnapura exceeded, by a substantial margin, the global mean (i.e. 0.074 oC decade-1) during the period from 1906 to 2005. Analysis of frequency distributions of annual mean air temperatures showed that the above increases have occurred because of a shift in the entire distribution of temperatures over time rather than due to a few extremely warm years. Four out of the seven locations (i.e. Anuradhapura, Kandy, Badulla and Nuwara Eliya) examined showed statistically significant (p<0.05) linear declining trends of decadal mean annual rainfall (RFa) with time over the whole 140-year period. The highest rate of rainfall decline was shown in Nuwara Eliya at 52 mm decade-1. Within the respective trends over the 140-year period, a period of significant (p<0.05) decline of decadal mean RFa could be identified in all locations except Colombo. In particular, Kurunegala has shown a rainfall decline of 121 mm decade-1 from the 1970s onwards. Kandy and Nuwara Eliya have also shown rainfall declines in the range of 64-67 mm decade-1 since 1940s and 1920s respectively. In all locations, mean RFa during the period from 1990 to 2007 was lower than that during the 1950-1989 period. The reductions ranged from 28 mm yr -1 at Ratnapura to 202 mm yr -1 at Kurunegala. Analysis of shifts in rainfall distributions show that rainfall reductions in the years of extremely lower and higher rainfall have contributed relatively more to the mean rainfall reductions in successive periods than rainfall reductions in the years of average rainfall. In all locations, RFa showed decreasing trends, of varying strengths, with increasing mean annual temperature, Ta, with Nuwara Eliya showing the highest rate of rainfall decline (371 mm oC-1). Analysis of monthly and annual rainfall data from 1950 to 1989 showed that the El Nino phenomenon reduced RFa during the following year in all locations, mainly because of rainfall reductions in June-July (South-West Monsoon) and January-February. From 1990 onwards, these post-El Nino RFa reductions have increased in all locations except Colombo and Ratnapura, where post-El Nino RFa has been higher than in normal years. Notably, in all locations, post-El Nino reductions of June-July rainfall have been absent since 1990, where RFa reductions have occurred because of reductions in January February and October-December (North-East Monsoon) rainfall.