科研之友
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摘要
Snow cover is an important component of cryosphere, and strongly affects the hydrology and climate. The eastern part of the Qinghai-Tibetan Plateau, one of the three major snow-covered areas in China, is the source region of Yellow River, which has great impact on both climate change and water resource system. Based on the Yellow River source region data of snow depth, meteorological and measured runoff from 1978 to 2016, the characteristics of snow cover and its influence on spring runoff of this area were studied through the Mann-Kendall test, linear analysis and correlation analysis. The results showed that:(1)From 1978 to 2016, the source region of Yellow River revealed a tendency of a delayed initial snow date, forwarded final snow date, and declination of both duration and number of snow days. Particularly, the initial snow date, the final snow date and the duration of snow days passed the significant tests of p <0.05, p<0.05 and p<0.01, respectively.(2)The annual average snow depth had no significant change from 1978 to 2016 in this area. However, it showed a significant upward trend since the end of the 21 century and passed the significance test of p<0.1.(3)In general, compared with the snow depth, the number of snow days has more impact on the spring runoff in the source region of Yellow River. More specifically, according to the sensitivity analysis of the data from 1978 to 2016, 1% change of the of snow day number would induce of 0.60% spring runoff change, while the same amount change of the snow depth would only induce 0.25% spring runoff change. In addition, the spring runoff in April and May is more sensitive to snow cover change than March due to the increased average temperature and the larger amount of melted snow.(4)Different precipitation and temperature generates different snow cover, which results different responses to spring runoff. The snowmelt runoff is advanced under the climate warming, which shows an upward runoff trend in March while a downward trend in April and May. Meanwhile, due to the change of the regional atmospheric water vapor content, the spring runoff in the Yellow River source region significantly increased since the end of the 21 century.
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