影响海河流域参考作物蒸散量的气象因子定量分析

摘要

Based on the daily data of 159 meteorological stations over the Haihe River basin during 1961-2014,the potential evapotranspiration (ET0) was calculated by Penman-Monteith equation to analyze the sensitivity coefficients of ET0 to meteorological elements including maximum temperature,minimum temperature,relative humidity,average wind speed and sunshine duration.Additionally,the dominant factors influencing ETo change were discussed combined with the multi-year relative variations of meteorological elements.The results show that annual mean ET0 over the Haihe River basin reduced significantly with the rate of 22.7 mm · (10 a)-1 from 1961 to 2014,and the mutation occurred in 1979.From the spatial distribution,ET0 reduced significantly in the most of the basin,except for the northwestern part.The sensitive coefficients of ET0 to meteorological elements were almost positive,except for relative humidity.Considering the sensitive coefficients of ET0 to meteorological elements and the multi-year relative variations of each element,the relative humidity and the maximum,minimum temperature were the factors causing the increase of ET0,the average wind speed and sunshine duration were the factors causing the decrease of ETo.The sensitive coefficients of ETo to average wind speed and sunshine duration were not the highest,but the average wind speed and sunshine duration decreased significantly and their relative variations were larger,so they contributed great to ETo and became the dominant factors of ETo change.To summarize,ET0 decreased significantly due to the decreasing of average wind speed and sunshine duration over the Haihe River basin.%基于海河流域159个气象站1961-2014年逐日气象资料,采用P-M模型计算该地区的参考作物蒸散量(ET0),分析海河流域ET0对平均最高、最低气温及相对湿度、平均风速和日照时数的敏感性,并结合各气象要素的多年相对变化率定量探讨ET0变化的主导因子.结果表明:海河流域年ETo以-22.7mm· (10a)-1的速率显著减少,在空间分布上,除流域西北部分地区呈增加趋势外,大部分地区ETo呈显著减少趋势.ETo对各要素的敏感系数除相对湿度外,其他均为正值.综合考虑ETo对各要素的敏感性及各要素的多年相对变化率发现,相对湿度及最高、最低气温是导致ET0增加的因子,平均风速和日照时数则是导致ET0减少的因子.虽然平均风速和日照时数的敏感系数不是最高,但其减小趋势显著,多年相对变化率较大,导致对ETo的贡献较大,成为海河流域ETo变化的主导因子,二者的显著减少造成了整个流域ETo显著减少的事实.