我国过去50a来降水变化趋势及其对水资源的影响(Ⅰ):年系列

Variation Trend of Precipitation and Its Impact on Water Resources in China during Last 50 Years (Ⅰ): Annual Variation

应用全国范围内的678个气象站1951—1998年长系列降水资料,用线性回归方法研究降水量、降水日数和降水强度的变化趋势,同时结合长江和黄河主要控制水文站同期的径流资料,研究径流对气候变化的响应.结果表明:近50a来年降水量表现出明显的区域性变化特征,东部地区降水日数减少显著,西部地区年降水日数以增加为主;日平均降水强度的变化趋势除西南地区有一带状的微量减少外,全国大部分地区表现为增加趋势.气候的上述变化趋势对我国干旱的西北地区有利,该区河流径流量有明显增加;另一方面,降水强度的增加导致洪水事件的濒发.但对干旱的华北、多雨的华东和华南地区却不利,华北呈现愈加干旱,华东华南愈多洪涝.黄河20世纪90年代持续的严重断流和长江淮河近10a的洪涝大灾频发,就是一个例证.

In this paper the changing trends of precipitation amount, days and intensity in China during the last 50 years are analyzed based on the long-term precipitation data at 678 meteorological stations in China, and the response of river runoff to climate change also analyzed based on the annual runoff data at the main hydrological stations of four biggest rivers by using the linear regression methodology. It is found that the annual precipitation in the past 50 years has an obvious region-dependence. A generally rising trend of the annual precipitation appears at most stations in the western region of China (bordered as the 103° E), and the same increasing trend occurs in South China and East China (in the lower reaches of the Yangtze River, the Yellow River and the Zhujiang River) and in the west of Northeast of China. However, a decreasing trend appears in North China and the east part of Northeast China, as well as in Shanxi province, Sichuan province and the southern Gansu province. Precipitation day displays a marked decrease in the eastern region of China. In most of China, the rainfall days have a positive trend character. An increasing trend in the daily-averaged precipitation intensity is found in most regions of China, except for a belt area in the southwest of China, where the intensity has a slight decrease.On one hand, such a climate change in China is probably benefited to easing the drought situation in Northwest China. It has been found that the river runoff in Northwest China increases markedly. However, the increase of precipitation intensity may lead to frequent occurrence of floods. On the other hand, the negative trend in precipitation brings disadvantage effects to the drought North China, rainy East China and South China, and thus causes more droughts in North China and more floods in East China and South China. The serious cut-off of flow during the 1990s in the Yellow River and the very frequent big flood disasters during the recent 10 years in the Yangtze River are the results from the precipitation change.