黄河中游河口-龙门区间陆面年蒸散量估算

Regional Evapotranspiration Estimation in Hekou-Longmen Section of the Middle Reaches of the Yellow River

论文采用多年平均流域水平衡模型,利用黄河中游河口—龙门（即河龙）区间1970～2000年水文气象资料,估算该区陆面蒸散量,并分析其时空变化特征。模型模拟值与水量平衡法计算值复相关系数达0.95,有效系数0.82,均方差19.3 mm。估算相对误差随湿润或干旱程度增强而增大。相对误差对降水量变化的敏感程度以西北干旱草原区最强,南部林区最弱。黄河中游河龙区间多年平均陆面蒸散量384 mm。整个区域陆面蒸散量呈递减趋势,20世纪70～80年代减少幅度较80～90年代剧烈。空间上前期表现为多中心变异格局,而后期则大致呈现南北梯度变化。表明干旱半干旱的河龙区间陆面蒸散量在空间和时间上的多变性。

Regional evapotranspiration（ET） is a complex process which is controlled by climate and catchments characteristics over various temporal scales.It is important to understand the spatial and temporal variability of annual ET in the rational water resources management,even in soil water conservation modeling in the Loess Plateau.The mean annual catchment water balance model established by Zhang et al.（2001） was used in this study to estimate the annual ET.The meteorological and hydrological data in this area covering 1970-2000 were employed to check the annual estimation accuracy and the spatio-temporal distribution examination of estimated ET.The accuracy test showed that the coefficient of determination（r2） reached 0.95 between modeled and observed annual ET in the whole Hekou-Longmen section,the index of agreement was 0.90,the coefficient of efficiency 0.82 and the root mean square error 19.3 mm.The estimated errors increased with precipitation or decreased with the increase of aridity.The error was most sensitive to the precipitation in the dry grassland in northern part of Hekou-Longmen section,and most insensitive in the forest land of northwestern part.The regional mean annual ET was estimated to be 384 mm and turned out to be a decreasing trend in 30 years.From the 1970s to the 1980s it showed a changing pattern of multicenters style with ET increasing in the southern part and decreasing in the northern part.While from the 1980s to the 1990s,it generally showed a changing pattern with linear style which indicated the reverse trend with the last decade.The regional annual ET in the Hekou-Longmen section of the Yellow River showed the big variability in spatial,as well as temporal scale.