中文摘要：

利用淮河流域26个气象观测站的观测资料,采用Penman-Monteith法计算流域的参考蒸散发量,结合参考蒸散发对气象因子的敏感性分析以及气象因子在1960—2008年的变化,定量评估气象因子变化对蒸散发的贡献程度,进而分析流域近50 a来参考蒸散发量的变化及其原因.结果表明：淮河流域绝大部分地区的年参考蒸散发总量呈下降趋势,淮河以北地区的下降趋势比淮河以南地区更为显著.造成这种变化的主要原因是太阳辐射量的减少和风速的降低,淮河以南地区受相对湿度变化的影响,下降幅度小.

英文摘要：

In this study, the reference evapotranspiration was calculated using the Penman-Monteith method based on the observed data from 26 meteorological stations in the Huaihe Basin. In order to understand the variation of meteorological factors and its causes in the basin over the last 50 years, the quantitative estimation of the contribution of the meteorological factors to reference evapotranspiration was conducted based on analysis of sensitivity of evapotranspiration to meteorological factors and variation of the meteorological factors from 1960 to 2008. The results show that for most parts of the basin there is a decreasing trend in the annual reference evapotranspiration, which is mainly caused by a significant decrease in the wind speed and radiation over the basin, and the decreasing trend to the north of the Huaihe River is more significant than to the south of the river, because the regions to the south of the river are influenced by relative humidity and have a weakly decreasing trend of reference evapotranpiration.