气候变化背景下中国陆地水循环时空演变

Impact of climate change on terrestrial water cycle in China

水循环是气候系统各子系统相互作用过程中一个最活跃的枢纽,受气候变化影响显著。本文采用观测和多套再分析数据,系统分析了1979年以来中国及各大流域大气水汽含量、降水、蒸散发和地表径流等水循环要素年际变化。研究发现,1979-2018年,中国陆地整层大气水汽含量和水汽收支呈显著上升趋势;水汽收支除在松花江和西南诸河略有下降,其余流域均呈上升趋势;降水除西北诸河流域呈现显著上升趋势外,其余流域变化不显著;蒸散发整体呈微弱增加,但南方大部流域呈现显著的减小趋势;除西北诸河径流显著上升趋势外,北方大部分流域地表径流呈现减少趋势,而南方流域的径流变化趋势复杂多样。相对1979-2000年,21世纪以来中国年平均气温上升约0.63℃,年降水量、大气水汽含量分别增加0.5%和1.2%,水汽总输入和输出量均减小,降水再循环率增加10.9%。进入21世纪,中国陆地水资源一级分区内循环均较前20 a活跃,降水再循环率除松花江和辽河流域外,均有所增加。其中,海河、黄河、淮河和西北诸河流域的水汽和蒸发形成的降水都有所增加;辽河流域蒸发形成的降水有所增加,但输入水汽减少导致流域降水减少最多;松花江、长江、珠江和西南诸河流域蒸发形成的降水增加,输入水汽减少导致降水略有减少;东南诸河蒸发形成的降水略有增加,但整体变化不大。

Water cycle is one of the most active processes in the interaction among ocean,land and atmosphere,and affected significantly by climate change.This paper evaluates the changes of water cycle components including precipitation,evapotranspiration,surface runoff and water vapor in China and ten river basins since 1979 based on ground based observations and reanalyses.Results show that the atmospheric water vapor and water vapor budget have shown significant increase trends during 1979-2018 in China.But,a weak downward trend of atmospheric water vapor was found at the Songhua River Basin and the Southwest River Basin spatially.Except for the Northwest River Basin,where annual precipitation increased significantly,changes of precipitation in other river basins were not significant.Areal averaged annual actual evapotranspiration increased slightly in China,but decreased obviously at the most River basins in South China.As for surface runoff,a clear increase trend was detected at the Northwest River Basin,but negative trends were found at the majority of River basins in North China,while trends were complex at the River basins in South China.Relative to 1979-2000,annual mean temperature in China increased by about 0.63℃,and annual precipitation and atmospheric water vapor increased about 0.5%and 1.2%,respectively,in 2000-2018.Meanwhile,both inflow and outflow of water vapor decreased,and precipitation recycling ratio increased by 10.9%.Spatially,the internal water recirculation was more active than before in 2000-2018 at the most river basins escept for the Songhua and Liaohe River basins in Northeast China.Precipitation produced by local evapotranspiration and inflow water vapor were both increased at the Haihe,Yellow,Huaihe and Northwest River Basins.At the Songhua,Liaohe,Yangtze,Pearl and Southwest River Basins,increase of precipitation from local evapotranspiration was offset by more significant declining of precipitation from infow water vapor,and this effect was more obvious at the Liaohe River Basin than others.Precipitation produced by local evapotranspiration has increased slightly,but overall change of precipitation was not significant at the Southeast River Basin.