近50年来长江—黄河源区气候及水文环境变化趋势分析

Changes of weather and hydrological environment for the last 50 years in the source regions of Yangtze and Yellow Rivers

对长江、黄河源区12个台站近50年来的温度、降水资料分析表明,近50年来长江源区平均升温0.61℃,黄河源区平均升温0.88℃;长江-黄河源区降水量在经过上世纪80年代高峰期后90年代呈现明显下降趋势,东部地区降水量减幅大于西部地区;在总体气候向暖干变化的同时,区域内春末夏初和冬季部分月份近50年来气候朝暖湿化方向发展。径流量在上世纪90年代呈现出较强的枯水期,然而由于气候变暖加剧了冰雪的消融,以冰雪融水补给为主的河流在温度升高的气候背景下径流量出现了较大幅度的增长。伴随着温度的升高和降水量的波动变化,近50年来区域内呈现出冰川、冻土加速消融,湖泊、沼泽疏干退化加剧的趋势。

Climate in the source regions of the Yangtze and Yellow Rivers has changed to warm-dry in last 50 years. This paper analyzed the data of temperature and precipitation of 12 weather stations in the region. It is found that the air temperature increased within past 50 years. The average increase amplitude is 0.88 ℃ in the region of Yellow River and 0.61 ℃ in the region of Yangtze River. The average annual temperature obviously increased in 1990s. During the last 50 years, the precipitation decreased especially in the east region. However, the precipitation increased during some months such as May and June in the west, and April, May in the east. So the climate has been changing to warm-wet within these months. By analyzing variations of runoff, the paper indicates that the surface runoff in the region has decreased since 1990s. The runoff evolution in the source region of Yangtze River experiences the process from dry to wet, and to dry again. However the runoff of rivers, such as Tutuhe River, increased in the past 20 years for its abundant recharge from the glaciers. Ablation of the glaciers and degradation of the permafrost expedited in the past 50 years especially in 1990s. At the same time, the area of the lakes and swamps reduced. The hydrological environment became worse gradually along with these changes.