Analysis Of Climate Change In The Last50Years And The Projection In The Future In The Yellow River Basin

First, the Yellow River Basin was divided into6sub-regions based on the different terrains and climate types. The rise of the river to Maqu Station, Maqu Station to Qingtongxia Station and Qingtongxia Station to Hekou Station are defined as the up reach sub-region No.l,2and3, respectively. Hekou Station to Yumenkou Station and Yumenkou Station to Taohuayu Station are defined as the middle reach sub-region No.1and2, respectively. Taohuayu Station to the end is defined as the lower reach sub-region. Then the changing characteristics and trends of temperature, precipitation in the whole basin and each sub-region are analyzed by using the observed data sets during1960-2010from229meteorological stations. Based on observational data of61stations from1961to2010, Trend and abrupt change of pan evaporation of Yellow River basin are analyzed, and the related climate factors are studied. The conclusion are as follows:The results showed that in the whole basin, temperature had increased about1.5℃, precipitation decreased with some fluctuations, so the general climate change trend of the basin was warm and dry.In the upper region, temperature had increased about2.0℃, and precipitation decreased, so the trend of the region was warm and dry. In the middle region, temperature had increased about1.3℃, lower than the average temperature of the whole region. The middle reach sub-region NO.1was typically warm and dry. In the lower reach sub-region, temperature had increased about1.1℃with rising rate less than other regions, and precipitation decreased by2.7%. so the trend of the region was warm and humid..The results show that a significant decreasing trend in annual mean evaporation has been found in the recent50years with an average rate of-29.0mm/10a and abrupt change occurs in1979. In the low region, the average rate of annual mean evaporation is-69.5mm/10a, presenting the most significantly decreasing trend compared to upper and middle region, with rate of-26.1mm/10a and-20.9mm/10a, respectively.In the spatial distribution, the most significant evporation decreasing region in annual and seasons of spring and summer lies in the source region of Yellow River, He Tao region and the north of HeNan. The regions with significant positive correlation of evaporation with temperature range, wind speed and sunshine duration are in accord with the regions where evaporation experienced an evident positive change. The regions with significant negative correlation of relative humidity with evaporation are in accord with regions where evaporation experienced an evident negative change. On the attribution, it is calculated that wind speed and temperature are the main influencing factors leading to the decrease of evaporation. In spring and summer, the main factors are wind speed and relative humidity, and temperature change and wind speed in autumn, and temperature and sunshine duration in winter.According to comparing the simulation of MdR, EdR, HdR and BdR on the climate change of Yellow River, the data of BdR simulates better. Compared to the results of50km data, the10km simulation can represent the spatial distribution better, and correct the high-value in the middle and low region. But there are little improvement in the precipition. The average temperature will increase in the future, and vary in different seasons and regions. The largest increase of temperature lies in the HeTao region, and the smallest one lies in the low region. In the end of21century, the increase of temperature is larger than the one in the middle of21century. And the precipitation will increase obviously in the future.