海河流域ET0演变规律及灵敏度分析

根据国家气象站1956-2000年逐日气象资料,采用Penman-Monteith公式和灵敏指数法,分析了海河流域潜在蒸发蒸腾(ET₀)的演变规律及与气象要素的灵敏关系。结果表明:全流域45年ET₀呈下降趋势,但年际间呈现4个阶段;逐旬呈倒"V"字型,61.6%集中于4月中旬到8月上旬。在空间上,年和旬值呈现上游小下游大。通过ET₀与气象要素演变的比较及灵敏性分析发现,全流域年ET₀演变与年均风速、日照时数以及短波辐射相似,与温度相反。旬ET₀演变与旬平均温度、实际水汽压、日照时数以及短波辐射相似,但对各要素的灵敏系数以短波辐射最大,其它要素则随时空变化,且彼此的灵敏系数相差较大。分析表明在气象要素的综合作用下,造成全流域ET₀降低的主要原因可能在于短波辐射、日照时数的变化。

Potential evapotranspiration evolution rule and its sensitivity analysis in Haihe River basin

Based on the daily climatic data from the nation weather station in 1956-2000,the paper employs the P-M equation and the sensitivity coefficient method to analyze the evolution rule of the potential evapotranspiration(ET₀)and the sensitivity relation of ET₀ to climatic variables in Haihe River basin.The results indicate that the annual ET₀ series appears decreasing trend with four different sub-stages in the recent 45 years.The multi-annual ten-day average ET₀ shows inverse "V" shape, and 61.6% of the whole ET₀ amount occurs in the middle-April to the up-August.In space,the multi-annual ten-day average and the annual ET₀ have an increasing trend from the upstream to the downstream.Compared with the evolution rule of the climatic variables and the sensitivity of ET₀ to them,the evolution rule of the annual ET₀ in the whole basin is similar to that of the multi-annual average wind speed,sunshine time and short wave radiation,and inverses to that of the multi-annual average temperature.The evolution rule of the multi-annual ten-day average ET₀ has same trend to that of the temperature,actual vapor,and sunshine time,as wel as the short wave radiation.However,in all the sensitivity coefficient of ET₀ to these climatic variables,that of ET₀ to short wave radiation is maximum in the whole year and the second water resources districts.The sensitivity of the ET₀ to any other climatic variables is different in time and space,and the values of sensitivity coefficients vary greatly.According to the analysis above,the ET₀cs decreasing trend in the whole basin may be caused by the change of short wave radiation and sunshine time.