四川省湿润气候区参考作物蒸散量趋势变化及成因分析

Change in Reference Crop Evapotranspiration from Humid Climate Region of Sichuan Province and Its Determinants

【目的】分析四川省湿润气候区参考作物蒸散量(ET0)的趋势变化及其影响因子,以期为农业灌溉提供合理的依据。【方法】根据雅安市1954—2009年逐日的气象资料,采用Penman-Monteith(PM)公式计算ET0,通过气候倾向率、Mann-Kendall法、通径分析对研究区域ET0的趋势变化与成因进行分析。【结果】ET0年际变化不稳定,多年平均值为861.2 mm,且呈现极显著的下降趋势(z=-3.06<-1.96),气候倾向率为9.3 mm/10 a;相对湿度无显著性下降趋势(z=-0.52),风速(z=-7.09)、日照时间(z=-2.61)、净辐射(z=-2.64)在1954—2009年都呈显著性下降趋势,而日平均温度(z=2.96)呈现显著性上升趋势;影响ET0的因素依次为净辐射、相对湿度、风速、日平均气温;采用辐射法中Pristley-Taylor法计算得到的ET0与PM法计算下的ET0相近。【结论】雅安市多年平均ET0呈显著性下降趋势;日照时间是影响ET0减少的主要因素;在气象资料缺失的湿润地区,可以采用Pristley-Taylor法代替PM公式来计算ET0。

【Objective】Evapotranspiration is the most important water loss from terrestrial ecosystems and understanding its spatiotemporal change is critical for improve water management.We took the humid region in Sichuan province as an example and analyzed the temporal change in reference crop evapotranspiration(ET0)as well as its determinants in the region.【Method】We calculated ET0 using daily meteorological data measured from 1954 to 2009 in Ya’an based on the Penman-Monteith(PM)equation first,and then analyzed the characteristics in its change as well as its determinants using the Mann-Kendall test and path analysis respectively.【Result】The annual ET0 over the 1954—2009 was 861.2 mm,but the ET0 had been in decline at 9.3 mm/10a.Although the relative humidity remained almost unhanged(z=-0.52),wind speed(z=-7.09),sunshine hours(z=-2.61)and net radiation(z=-2.64)had all been falling accompanied by an significant rise in daily mean temperature(z=2.9).Path analysis revealed that the factors that impacted ET0 more were net radiation,relative humidity,wind speed and daily average temperature.The ET0 calculated by the Pristley-Taylor method was comparable to that estimated from the PM equation.【Conclusion】The annual average ET0 in Ya’an has been declining,and the sunshine hours is the main determinant.The Pristley-Taylor method can be used to calculate ET0 for the humid areas lacking of meteorological data.