北京地区参考作物蒸散量变化趋势及其主要影响因素分析

利用1951~2007年北京气象站的气象资料,采用FAO56 Penman-Monteith公式(PM公式),计算了北京地区每日的参考作物蒸散量(ET0),分析了北京地区各气象要素和ET0的变化趋势,利用敏感性分析找出影响ET0变化的主要因子。研究结果表明:在1951~2007年期间北京地区的平均相对湿度和日照时数呈下降趋势,平均温度呈升高趋势,平均风速呈现先增加(1951~1972年)后下降的趋势(1973~2007年);饱和水汽压差升高造成的ET0值正变化不仅抵消了净辐射降低对ET0造成的负影响,还使得参考作物蒸散量表现为逐渐增加趋势;敏感性分析显示相对湿度和温度是影响北京地区年ET0变化的主要因子;在年内,夏季(6~8月份)对ET0影响最大的因素为日照时数,在其它时间段内,温度对ET0的影响最大。

Changing trend and dominated meteorological variables of reference crop evapotranspiration in Beijing

Daily reference crop evapotranspiration(ET_0)in Beijing from 1951～2007 was computed with FAO Penman-Monteith equation (PM) to find the changing trends of meteorological variables and ET_0 and to find the dominated meteorological variables of ET_0 using a sensitivity analysis method. Results showed that in the past 57 years, the relative humidity and daily sunshine hours decreased, the air temperature increased, the average wind speed increased from 1951～1972, and then decreased during 1973～2007. Although net radiation had negative effect on ET_0, the increasing of saturated vapour pressure deficit made ET_0 increasing slowly. Sensitivity analysis on yearly ET_0 indicated that the relative humidity and air temperature were two dominated meteorological elements to ET_0 in Beijing area. Within a year, the number of daily sunshine hours is the dominating element to ET_0 in summer (June～Aug.) and air temperature is in other seasons.