海河流域50年来参考腾发量的时空变化规律及其影响原因

根据海河流域34个站点1957—2007年逐日实测气象资料,结合旋转正交函数(REOF)、参数t检验法和Mann-Kendall检验方法对海河流域参考腾发量(RET)及其相关的4个气象变量(平均气温、风速、相对湿度和日照时数)的时空演变特征进行了分析,在此基础上,分析了RET对气象变量的敏感性,定量评估了气象变量对RET变化的贡献程度,探讨了影响RET变化的可能原因.结果表明,过去50年,海河流域59%的站点RET呈现显著下降趋势,主要分布在东部平原区,呈现显著上升趋势的站点主要分布在西部山地区.依据REOF分析结果,海河流域可以划分为3个区域:西部区、北部区和东部区;北部区和东部区的RET都呈现出显著的减少趋势,而西部区则呈现出显著的增加趋势;相对湿度是对RET最敏感的气象变量,风速和日照时数次之,平均气温对RET的敏感性最小;海河流域西部区RET的增加主要是由该区域显著减少的相对湿度所引起的,而北部区和东部区显著下降的风速和日照时数是导致这两个区域RET减少的主要原因.

Spatial and Temporal Patterns of Reference Evapotranspiration Changes and Their Causes in the Haihe River Basin during the Past 50 Years,China

In this study the spatial and temporal patterns of trends of reference evapotranspiration and four related meteorological variables(i.e.air temperature,wind speed,relative humidity and sunshine duration)at 34 meteorological stations during 1957—2007 in the Haihe River Basin were detected using rotated empirical orthogonal function(REOF),parametric t-test and Mann-Kendall test.The sensitivity of the reference evapotranspiration to the four major meteorological variables was analyzed,and the possible causes and quantitative contributions of the major meteorological variables to the reference evapotranspiration trends were investigated in the Haihe River Basin.The results showed that decreasing trends in annual RET were observed at 59% stations located mostly in the eastern and southern plain area of the Haihe River Basin.While increasing trends in the annual RET were observed at four sites located mainly in the western mountain region of the Haihe River Basin.The Haihe River Basin can be divided into three sub-regions(i.e.western,northern and eastern sub-regions)based on the results of REOF analysis.The RET presented significant decreasing trends in northern and eastern regions,while the western region showed significant increasing trends.The most sensitive variable for the RET was relative humidity followed by wind speed and sunshine duration in the Haihe Rvier Basin,and the least sensitive variable was air temperature.The increasing trend of RET in western region was mainly caused by the significant decreases in relative humidity,and the decreasing trends of wind speed and sunshine duration were largely responsible for the decreasing trend of the RET detected in northern and eastern regions.