近50年来海拔高度对参考蒸散发变化趋势的影响研究——以四川省为例

Studies on the Influence of Altitudes on the Trend of Reference Evapotranspiration in Recent 50 Years:A Case Study of Sichuan Province

参考蒸散发ET_0是水文气象研究中关键变量,其在不同海拔区域对气象要素的响应特征不尽相同。基于四川省境内不同海拔区域的38个气象站点的基础数据,利用FAO-56 Penman-Monteith方法计算其1970—2016年共47年逐日的参考蒸散发ET_0,通过滑动T检验识别ET_0序列存在的突变点,并分析ET_0以及相关气象要素在四川省不同海拔的分布特征,采用敏感度分析法以及贡献率法分析气象要素在不同海拔对ET_0变化的响应。结果表明:(1)ET_0序列随海拔升高呈先增加后减少的趋势,低海拔(低于1 500 m)、中海拔(1 500～3 000 m),高海拔(高于3 000 m)ET_0年均值分别为745、1 001、964 mm·a^(-1);(2)1998年是序列的突变点,在1970—1998年有显著的下降趋势,而后序列显著增加;突变点前后相对湿度、日照时间和风速趋势发生改变,而日平均温度在1998年前后均保持增加趋势;(3)敏感度分析结果表明,相对湿度对ET_0响应最大,日照时间最小;(4)贡献度分析表明,相对湿度、风速和日照时间对于ET_0的变化的贡献率在1998年发生转折,而温度对于ET_0的变化均为正贡献;(5)在中海拔和低海拔区域,参考蒸散发变化主要驱动要素为风速,而在高海拔则主要为温度及相对湿度。该研究结果将有助于深入了解气象要素对ET_0变化的响应,为四川省水资源规划与管理提供科学依据。

Reference evapotranspiration(ET0),an indicator of global climate change,makes different responses to the meteorological variable at different altitudes.The present study,based on the basic data of 38 meteorological stations in different altitude areas in Sichuan province,investigated the attribution of the change of the daily ET0 and used the FAO-56 Penman-Monteith method to calculate its reference evapotranspiration ET0 for the period 1970-2016 for a total of 47 years.The Sliding T test was used to identify the breakpoint.Sensitivity Analysis and contribution rate analysis were also used to detect the meteorological elements in response to ET0 at different altitudes.An insignificant increasing tendency of ET0 was observed on the time scale.1998 was a mutation point of the sequence,with a significant downward trend in 1970-1998 and a significantly upward trend after 1998.The ET0 in partitionⅠ(low altitude),Ⅱ(middle altitude)andⅢ(high altitude)increased first and then decreased with altitude.In the meteorological elements,the relative humidity(RH),daily average temperature(t),sunshine duration(S)and daily mean wind speed(WS)was the closest meteorological factors to ET0.Among them,the trend of RH,S,WS was changed in 1998,while t maintained an increasing trend.The sensitivity analysis results showed that RH had the greatest response to ET0 while S had the minimum.The contribution of WS,S,RH to the change of ET0 turned in 1998 with a negative contribution in 1970-1998 and a positive contribution after 1998,while t was a positive contribution to the change in ET0 all the time.In the regions below 3 000 m,the ET0 was mainly affected by WS,while in those areas above 3 000 m remainly affected by t and RH.The results of this study will help to understand the response of meteorological elements to the changes of ET0 so as to provide scientific basis for the water resources planning and management.