西北地区生长季参考作物蒸散变化成因的定量分析

基于FAO Penman-Monteith 公式计算了我国西北地区126 个测站1961-2009 年的生长季(4-10 月) 参考作物蒸散(ET₀) 对平均气温、风速、相对湿度和太阳辐射的敏感系数，并结合各气象因子的多年变化特征定量讨论参考作物蒸散变化的原因。结果表明：风速和气温的敏感性虽然相对较低，但因其显著变化，成为引起ET₀变化的主导因子，贡献达到-5.22%和3.29%；太阳辐射和相对湿度敏感性较大，但因变化小，贡献仅为-0.76%和0.63%。空间上，气温在西北地区对ET₀ 变化多为正贡献，风速和太阳辐射多为负贡献；相对湿度在西部多为负贡献，东部为正贡献。估算的4 个气象因子共同作用引起的ET₀变化在趋势、数值和空间分布上均与ET₀的实际变化基本一致，两者的相关系数高达0.99，表明结合敏感性分析和气象因子的多年变化来解释西北地区ET₀变化的原因兼具合理性和可行性。而且该方法弥补了趋势分析法、相关分析法和敏感性分析法的不足，为定量分析ET₀变化成因提供一条新思路

Quantification of the Causes for Reference Crop Eapotranspiration Changes in Growing Season in Northwest China

Based on the FAO-56 Penman-Monteith equation, the changes of reference crop evapotranspiration (ET₀) were studied by analyzing the sensitivity coefficients of ET₀ to air temperature, wind speed, relative humidity and shortwave radiation together with their relative changes in growing season in Northwest China using a 49-year dataset. The results show that the changes of ET₀ are primarily attributed to wind and air temperature due to their significant trends. Shortwave radiation and relative humidity have negligible effects on ET₀ for their insignificant trends. The positive contribution of temperature and the negative contribution of wind and solar radiation are observed in most regions, but the contribution of relative humidity is positive in eastern part and negative in western part. The consistence between the actual ET₀ changes and the estimated ET₀ changes calculated by the contribution of four meteorological variables indicates that the method based on sensitivity coefficients interpreted together with actual changes in variables to quantify the impact of each variable on the ET₀ trend is reasonable.