Analysis of pan evaporation trend and its impact factors in Guizhou Province

以贵州境内18个气象站1961-2001年逐日气象观测数据为基础,采用Mann-Kendal非参数检验方法、相关分析和主成分分析方法对贵州近41年来蒸发皿蒸发量及其主要影响因子(太阳净辐射、气温、相对湿度和风速等)进行了相关性及趋势性分析.结果表明:近41年来,贵州年平均蒸发皿蒸发量呈显著下降趋势,通过99%的置信度检验,蒸发量的下降主要表现在冬、春、夏三季.从区域分布来看,蒸发皿蒸发量整体上东部及西北部分地区显著减少,其他地区趋势变化不明显.蒸发皿蒸发量下降的主要原因是太阳净辐射的显著下降.;Based on daily meteorological data of 18 observations from 1961 to 2001 within Guizhou Province, Mann-Kendall trend test, correlation analysis and principal component analysis were applied to determine trend of pan evaporation and its relation with meteorological factors (net solar radiation, temperature, relative humid, wind speed etc.). Analysis results demonstrate: pan evaporation presents a significant decrease trend in the 41 years (99% confidence level). This decrease trend is especially more significant in winter, spring and summer seasons. Spatially, significant decrease of pan evaporation occurs in the east area and part of the west area, and seldom occurs in the other areas. The pan evaporation decrease is primarily resulted from reduction of net solar radiation.