变化中的参考作物蒸散量及其对气候的响应

作为重要的水文气象参数，参考作物蒸散量（ET0）在全球生态系统中发挥重要作用。为深化认识湿润气候区ET0变化，基于湖南省87个气象站1960~2015年逐月气候资料，应用Penman Monteith（P M）模型估算ET0，利用线性趋势、Mann Kendall检验、反距离加权插值等分析了ET0及主要气候因子的时空变化，采取逐〖JP〗步回归函数来确定P M方程所涉及的气候因子对ET0变化的贡献。研究表明：年均ET0降幅为-3346 mm/10 a，〖JP+1〗日照时数和风速下降是ET0减少的主要原因，而相对湿度下降提高了ET0。春、夏、秋、冬四季ET0变化幅度分别为2966、-5451、-0922、-0207 mm/10 a，春季ET0增加是由相对湿度下降和最高气温上升引起的，夏、秋、冬三季ET0减少主要与日照时数和风速下降有关。风速、相对湿度、日照时数呈下降趋势，而气温、降水、湿润指数呈上升趋势，后者表明气候暖湿化趋势。气候变化背景下ET0显示出不同时间尺度（年、季）空间分布的多样性

Changing Reference Evapotranspiration and Effects of Climatic Factors

As a critical hydro meteorological parameter, reference evapotranspiration (ET0) plays an important role in the global ecosystem. In order to deepen the understanding of how ET0 changes in humid regions, we calculated ET0 by using the Penman Monteith equation and data from 87 meteorological stations in Hunan Province from 1960 to 2015. We applied linear trend, Mann Kendall test and inverse distance weighting interpolation methods for the analysis of spatiotemporal variations of ET0 and major meteorological variables, and selected the variables involved in the equation to identify the contribution to variability of ET0 using stepwise regression. Results indicated that: (1) average annual ET0 decreased at a rate of -3346 mm per decade. The declining trend of ET0 is mainly explained by the decline in sunshine duration and wind speed. On the contrary, dropping in relative humidity increases ET0 to some extent; (2) ET0 in spring was found to increase significantly (2966 mm per decade) , attributing to the decrease in relative humidity as well as the rise in maximum temperature, while ET0 decreased at a rate of -5451, -0922, -0207 mm per decade in summer, autumn, and winter, respectively; (3) the downward trend of ET0 in the three seasons was mainly related to the decline in sunshine durition and wind speed; (4) Annual wind speed, relative humidity and sunshine duration decreased while temperature, precipitation and wetness index showed an upward trend, suggesting a warming-wetting trend in Hunan Province; and (5) Spatial distribution of ET0 in Hunan Province under changing climate differed significantly among various regions both over annual and seasonal scale