近40a来江河源区生态环境变化的气候特征分析

Climatic Features of Eco-Environment Change in the Source Regions of the Yangtze and Yellow Rivers in Recent 40 Years

利用月气象资料,对过去40a江河源气候变化特征进行分析,并与全球、全国、青藏高原进行了比较.结果表明:江河源区气温具有增暖趋势,近40a两地年平均气温分别增加约0 8℃和0 7℃,为高原异常变暖区.黄河源区变暖的主要特征是最低气温变暖,日照时数增加;最低、最高气温的显著变暖,以及较黄河源区增加更长的日照时数是长江源区变暖的主要特征.长江源区冬季变暖的作用不是主要的,春季、夏季和秋季的变暖作用比冬季还要大;黄河源区的变暖也并不主要是冬季变暖造成的,秋季变暖的作用与其相当,其它季节的变暖作用也不能忽视.近40a来江河源区降水量略有增加,主要体现在20世纪80年代中后期以来春季与冬季降水量的明显增加,夏季降水量虽然总体上没有明显变化,且局地夏季降水量呈持续减少趋势.与全球、全国以及高原区对比显示,江河源区对全球气候变暖的响应最敏感,变暖首先从长江源和整个高原发端,之后15a.黄河源和全国才进入显著温暖期.黄河源与长江源北部降水量的增加表明,气候变暖有利于高原增加降水量.

Based on monthly data of air temperature, precipitation, maximum and minimum air temperature, duration of sunshine, the features of climatic change in the source regions of the Yangtze and Yellow Rivers are analyzed comprehensively over the last 40 years, and the climate changes in the source regions of the Yangtze and Yellow Rivers are compared with that in the Tibetan Plateau, in whole China and in the globe. It is found that air temperature in the regions as a whole has a rising trend in the recent 40 years with a rising amplitude of 0^7～0^8 ℃ in annual air temperature. So the source regions of the Yangtze and Yellow Rivers are one of unusual warming areas on he Tibetan Plateau. Major warming characteristics are increase in the minimum air temperature and duration of sunshine in the source regions of the Yellow River. Great increase in the maximum and minimum air temperatures and long duration of sunshine, longer than that in the source regions of the Yellow River, are the main features of climatic warming in the source regions of the Yangtze River. Increasing air temperature is not chief in winter, while warming in spring, summer, and autumn is greater than that in winter in the source regions of the Yangtze River, unlike in the Tibetan Plateau, the whole China and the globe. Warming is not the result of increasing air temperature in winter in the source regions of the Yellow River. Warming in autumn amounts to that in winter. Moreover, warming in other seasons cannot be neglected. Precipitation is slight increase in the source regions of the Yangtze and Yellow Rivers in the recent 40 years. But increase in precipitation reflects mainly on the noticeably increasing precipitation in winter and spring after the middle and later 1980s. As a whole, a continuous decreasing trend of precipitation can be seen in some regions, although precipitation in summer has no marked change. Comparison of climate changes in the globe, in the whole China, and on the Tibetan Plateau shows that the response of climate in the source regions of the Yangtze and Yellow Rivers to climate warming is most sensitive. Climate warming firstly began in the source regions of the Yangtze River and the Tibetan Plateau. 15 years later, markedly warming began in the source regions of the Yellow River and the whole China. Increase of precipitation in the source regions of the Yellow River and in the northern source regions of the Yangtze River indicates that climate warming is favorable for increasing precipitation on the Tibetan Plateau.