中文摘要：

采用Mann—Kendall趋势检验方法、完全相关系数法及多元线性回归模型分析了中国全域及其各气候区近50年的蒸发皿蒸发量变化趋势及原因。结果表明．中国蒸发皿蒸发量存在减少趋势，区域平均减少速率为17．2mm／10a；其中湿润区减少速率最大，为29．7mm／10a；半干旱半湿润区次之，为17．6mm／10a：干旱区最小．为5．5mm／10a。四季中，夏季减少速率最大，全国平均减少速率为16．2mm／10a，其次为春季，为9．7mm／10a，秋冬两季减少速率较小。中国蒸发皿蒸发量存在显著减少趋势的地区主要分布在湿润区的长江中下游地区、华南地区和云贵两省．半干旱半湿润区的黄淮海地区、山东半岛和藏东地区．以及干旱区的新疆、甘肃中部和青海省等。完全相关系数法分析表明，气温日较差和平均风速的减小与蒸发皿蒸发量的减少具有最显著的相关性．是蒸发皿蒸发量减少的影响因子。气温日较差的减小主要由云量和人类活动所引起的气溶胶及其他污染物的增加引起．这导致到达地面的太阳辐射强度减弱：而平均风速的减小则主要与全球变暖背景下亚洲冬季风和夏季风减弱导致我国平均风速的减小有关．

英文摘要：

Pan evaporation, as a measurement of atmospheric evaporative demand, has traditionally been used for agricultural water management. The changing trend of pan evaporation also attracts attentions from the hydrological community worldwide due to its indicative meaning in hydrological cycles. In this study, the changing trend of pan evaporation in China over the past 50 years was analyzed by using Mann-Kendall test method. The results show that there is a decreasing trend in most of the observations on pan evaporation in China, with an average rate of 17.2 mm/10a in China. In the humid region, the decreasing rate was 29.7 mm/10a, presenting the most significantly decreasing trend, while the decreasing rate were 17.6 mm/10a and 5.5 mm/10a in the semi-arid/sub-humid region and arid region, respectively. Temporally, most significant decreases occur in summer with a rate of-16.2 mm/10a; then, -9.7 mm/10a in spring; the decreasing rates in autumn and winter are relatively low. On the attribution, we calculated the complete correlation coefficients of 7 climate factors with pan evaporation. And decreases in diurnal temperature range and wind speed were found to be the main influencing factors leading to the decrease of pan evaporation. The decrease in diurnal temperature range might relate to the increase of aerosol as well as the other pollutants under the circumstance of global warming, which is one of the main features in the context of climate change; and the lowering of wind speed might be associated with the weakening of the Asian winter and summer monsoon under the global climate warming.