华北山区短时段参考作物蒸散量的计算

短时段参考作物蒸散量的估算是研究华北山区小尺度范围内的水分循环和转化的重要环节.因受观测条件的限制,北方半湿润半干旱山区短时段参考作物蒸散量的研究相对较少.本文利用FAO Penman-Monteith公式、FAO Penman修正式和Priestley-Taylor公式对华北山区东台沟小流域观测到的4个月的气象数据进行了逐日的参考作物蒸散量计算,结果显示,FAO Penman修正式的计算值比FAO Penman-Monteith公式的计算值平均偏大16%左右,而且经过统计分析,它们具有很好的相关性,即在代表流域内使用FAO Penman修正式计算出参考作物蒸散量之后,再乘以一个折算系数(如0.84),即可得到与FAO Penman-Monteith公式的计算值较为相近的结果;而Priestley-Taylor公式的计算值与FAO Penman-Monteith公式的计算值相比,差异比较显著.分析其原因,我们认为是由于Priestley-Taylor公式没有考虑空气动力项对参考作物蒸散量的影响.因此,如果在华北山区使用Priestley-Taylor公式计算参考作物蒸散量,必须根据季节对公式中的常数项α重新进行修正.本文通过对2003年8月～2004年8月期间逐日计算得到的ET0(P-T)和ET0(P-M)值进行对比分析后,给出了修正后的不同季节的α值,为华北山区计算作物蒸散量提供了依据.

Reference Crop Evapotranspiration Calculation in Short Interval of Mountainous Area in North China

It is important to estimate the reference crop evapotranspiration (ET0) in short inter val not only to meet the need of real time flood forecast and agrometeorology forecast but also to accelerate researches on water cycle and transfer in small catchment in North China. Limited by the observing apparatus and local geographical condition, the studies of the reference crop evapotranspiration in short interval have rarely been done in semi-humid and semi-arid mountainous area of North China. With four representative months (Aug. 2003, Nov. 2003, Feb. 2004, May 2004) detail data from standard automatic weather station in an experimental catchment named as Dongtaigou, daily ET0 is calculated by FAO Penman-Monteith equation(ET0(P-M)),FAO Penman equation(ET0(P)), and Priestley-Taylor equation(ET0(P-T)), respectively. The results show that the average calculated value from ET0(P) is 16% higher than that from ET0(P-M). And two sets of calculated data have a very good correlation. Multiplying a constant (e.g. 0.84), the ET0 calculated by ET0(P) in the experimental catchment is approximatively equal to the value from ET0(P-M). However, the calculated values from ET0(P-T) and those from ET0(P-M) have lower correlation. Failing to consider aerodynamic influence in Priestley-Taylor equation should be the reason for the difference. If Priestley-Taylor equation is used to estimate short-interval reference crop evapotranspiration in the study area, the parameter in Priestley-Taylor equation should be modified for different season. In this paper, the comparative analysis between calculated daily results by Priestley-Taylor equation and Penman-Monteith equation has been done based on the observing data from Aug. 2003 to Aug. 2004 and the parameter in Priestley-Taylor equation for different season has been suggested.