ET_0变化趋势分析及估算模型研究——以新乡站为例

【目的】参考作物蒸散量(ET_0)的估算是计算作物腾发量的基础,也是区域水资源评价与灌溉政策制定的前提,因此,研究ET_0变化趋势与估算模型能够对该地区农田灌溉用水预报提供基础支持,进而为灌溉制度的制定以及水资源高效利用提供科学依据。【方法】以河南新乡气象站1962―2016年气象资料为基础,运用Penman-Monteith模型计算ET_0序列,Mann-Kendall趋势检验法对年及季节尺度ET_0序列变化趋势进行分析,并用均值生成函数模型对其进行了拟合与验证。【结果】①新乡地区年尺度ET_0序列在1975―2016年间呈减小趋势,并在1985―2004年、2006年显著;②新乡地区春季ET_0序列在1982―1983年及1988―2003年间呈显著的减小趋势,夏季ET_0序列在1980―2012年间呈显著的减小趋势。③均值生成函数模型在对年尺度ET_0序列进行拟合时,其一致性系数达到0.83,绝对误差与相对误差分别在-120.8～120.0 mm及-14.0%～18.2%之间。④均值生成函数模型在对季节尺度ET_0序列进行拟合时,其一致性系数在春、夏、秋、冬各季节分别达到0.85、0.81、0.88及0.89,绝对误差分别在-60.2～64.3、-64.4～58.9、-39.6～32.8、-37.0～25.1 mm之间,相对误差分别在-20.1%～36.7%、-22.1%～32.1%、-18.0%～22.9%、-23.9%～24.6%之间。【结论】新乡地区年尺度ET_0序列在1985―2004年间显著减小,均值生成函数模型在对年及各季节尺度ET_0序列进行拟合时整体效果较好,因此,可通过其进行年及季节尺度ET_0序列的估算,且其在秋、冬二季的拟合效果明显好于春、夏二季。

Change in ET_0 and the Model to Estimate it:A Case Study for Xinxiang

【Objective】Reference crop evapotranspiration(ET_0) is an important parameter in many hydrological and ecological processes. It is also needed in irrigation management. This paper presents a method to estimate the change in ET_0 based on data measured from a weather station in Xinxiang, Henan province.【Method】We calculated annual and seasonal ET_0 using the Penman-Monteith formula based on meteorological data measured from1962 to 2016 at a meteorological station in Xinxiang. The Mann-Kendall test and mean generating function model were used to analyze any possible trend in the ET_0 at both annual and seasonal scales.【Result】①Annual ET_0 was in decline from 1975 to 2016, especially from 1985 to 2004 and in 2006. ②Spring ET_0 was in decline from1982 to 1983 and from 1988 to 2003, and summer ET_0 dropped from 1980 to 2012. ③The mean generating function model fitted the annual ET_0 well, with a consistency coefficient of 0.83, and absolute and relative error of-120.8～120.0 mm and-14.0%～18.2%, respectively. ④The consistency coefficient of fitting the mean generating function model to the seasonal ET_0 was 0.85, 0.81, 0.88 and 0.89 for spring, summer, autumn and winter respectively, the associated absolute error was-60.2～64.3 mm,-64.4～58.9 mm,-39.6～32.8 mm and-37.0～25.1 mm, and the associated relative error was-20.1%～36.7%,-22.1%～32.1%,-18.0%～22.9% and-23.9%～24.6%, respectively.【Conclusion】The annual ET_0 in Xinxiang area had been in decline from 1985 to 2004, due to its decrease in spring and summer. The mean generating function model can fit both annual and seasonal ET_0, and can thus be used to estimate the annual and seasonal ET_0. The fitting of the mean generating function model to the autumn and winter ET_0 was better than fitting to the spring and summer ET_0.