黄河流域近40年蒸发皿蒸发量的气候变化特征

Changes of pan evaporation in the recent 40 years over the Yellow River Basin

利用黄河流域及其周边123个气象站1961～2000年20cm口径蒸发皿资料,分析了黄河流域蒸发皿蒸发量的气候变化趋势。结果表明,就整个流域平均而言,尽管在1960～2000年期间,黄河流域年平均温度升高了0.6℃,但蒸发皿蒸发量却呈明显下降趋势,黄河流域年蒸发皿蒸发量在20世纪80～90年代较60～70年代下降了136mm,下降幅度为7.5%;蒸发皿蒸发量的下降主要表现在夏季和春季,秋季和冬季不明显。对蒸发皿蒸发量气候变化的空间分析表明,局部区域与整个流域的气候变化趋势并不完全同步,黄河流域上游和下游蒸发皿蒸发量呈下降趋势,中游呈持平并略有上升趋势。

Evaporation(evapotranspiration),on the one hand,is an important component in the heat and water balance of the Earth's surface,and is the component of the hydrologic cycle most directly influenced by land-use and climate change.On the other hand,evaporation(evapotran-spiration)consumes much of the water and energy that are available on the surface of the earth and therefore influence all hydrological and most meteorological processes.Basic knowledge for evaporation change over global or regional scale redounds to understand the law and causations of climate change.Up to now,studies on global climate change are,more and often,concerned with temperature and precipitation.Researches on the influence of climate change on evapora-tion(evapotranspirtation)are in small numbers.Based on observational data from1960～2000of123meteorological stations,near and in the Yellow River Basin,the spatial and temporal distri-butions of trends for pan evaporation are studied.The results show that,although the annual mean air temperature over the Yellow River Basin has,on average,increased0.6℃over the past40years,the rate of pan evaporation over the Yellow River Basin has,on average,steadily de-creased,especially in summer and spring.Compared with the1960s～1970s,the rate of annual pan evaporation of the1980s～1990s has decreased136mm or7.5%.Spatial distribution of the change rate shows that this trend is general but not universal,pan evaporation has significantly decreased over the upper and lower reaches of the Yellow River Basin,and increased in a small degree over the middle reaches of it.