Analyzing Climate Change Trends And Abrupts In Shiyang River Basin For 47 Years

Climatic shift happens from warm-dry to warm-humid in Northwest China in 1987, especially the mid-west area, which is the result of the complex water cycle drived by the global wanning. Not only in the academic field but also in the ecological environment and the social economy, it has the significant real value and the profound strategic meaning. But now the speed and degree in the spatio-temporal change of the phenomenon is not really clear. The Shiyang River basin is located in Northeast edge, Qinghai-Tibet plateau and the regional climate system is complex because many kinds of climate systems have a lot of influence on it. So while climatic shift happens in mid-west northwest, the climate in Shiyang River basin is still controlled by warm-dry. But the concerned experts persons forecast that the drought in eastern area will end very quickly and the climatic shift from drought to flood in north China may be happened in the future for 10～20 year. There are problems raised that whether the latent signal on climatic shift from warm-dry to warm-humid exists. Does it wound happen in the future? Those problems are worth discussing. Using observed data of average temperature, the precipitation and the evaporation month by month for 1960～2006 in Shiyang River Basin, this study analysis the tendency of climatic change and climatic abrupt from different scales, the spatial distribution characteristic and various meteorological element relations by many kinds of statistical analysis method, including sequence trend analysis and the sudden change examinations. Main research contents and conclusions include two parts:(1) Climate changed from cool-dry to cool-humid to warm-dry for decades in Shiyang River Basin. Since 1980, temperature had been increasing, most which was in 1980s¹990s. The temperature change is an increase for 47 years with a 99% confidence interval, the magnitude of which is larger than mean of China temperature. The warming of temperature over year is mainly due to increasing largely and remarkably in winter and spring. There is a little increase in precipitation, especially in summer, but with a low confidence. Wuwei and Yongchang area obviously increases. The evaporation has a decrease for years with a low confidence, the magnitude of which is larger in Wushaoling, Wuwei and Yongchang, especially Wuwei. And the evaporation in summer decreases significantly. May be the climate change in summer is a latent signal of shift from warm-dry to warm-humid in Shiyang River Basin.(2) By Mann-Kendall, an analysis of climate abrupt is given for 1960～2006. While many methods, such as MTT, Yamamoto, are used in the same data for validity. The results indicate abrupts in 1996 of average temperature and evaporation. Compare to the average temperature for 1960～1995, the temperature for 1996～2006 has increased by 1.3℃. There are sudden changes in 1996, 1996, 1985 separately conesponding to spring, fall and winter temperature,earlier winter. Compare to temperature, the climate abrupt of precipitation and the evaporation is more complex, especially precipitation. May be there are alternate abrupt in precipitation and evaporation. In space scale, temperature of year has a sudden change in 1993 in Wushaoling with high height. And middle and lower reaches area are consistent with the basin, confirming the high elevation area is more sensitive to global warming future.(3) There are many complex reasons for climate change in Shiyang River Basin, including global wanning and human activities. Many factors, such as CO₂ concentration and water vapor content, atmospheric circulation, terrain character and LUCC, have important influences on climate change in Shiyang River Basin.