The Change Characteristics of Precipitation and Its Temporal Distribution Homogeneity in Hexi Region of China in Recent 50 Years
近50年河西地区降水量变化特征及时间分布均匀度变化

Hexi, located in semiarid area of northwestern China, is a commodity grain production base in Gansu. It experienced a rising trend in annual temperature, strong rainfall variability and drought frequency during the past decades. Therefore, it is necessary for us to study on climate in order to improve farming production. Based on the monthly rainfall data from 1960 to 2009 at 13 meteorological stations over Hexi area and the method of linear regression and inverse distance weight, this paper has analyzed the spatial and temporal variability of precipitation during the past 50 years, and then on this basis, it has studied the precipitation homogeneous degree in Hexi area with Gini Coefficient. The results show that annual precipitation was small in the 1960s but it began to increase in the 1970s and from 2000, its increase rate started to be larger than that in 1980s and 1990s. It was also found that the average precipitation of all areas shows the spacial diversity. The precipitation tendency rate in Hexi area is -3.88mm10a-1 in the year, 2.33mm10a-1 in spring, 5.25mm10a-1 in summer, -3.27mm10a-1 in autumn and -2.32mm10a-1 in winter, and only the winter precipation tendency rates in eastern and central regions are significant at the 0.05 level. In general, there is a large inter-annual change in precipitation. After entering 2000, the distribution of the precipitation is more and more uniform and the area with uneven precipitation also change. According to the distribution function of Gini Coefficient, the precipitation is relatively homogeneous in the 1960s and 1990s, but not in 1980s. In 1960s, 1970s and 1980s, areas with uneven precipitation were mainly concentrated in the western region but they gradually shifted to the central and eastern regions in the 1990s. Because of the fragile eco-environment, it would be a great challenge for areas with uneven precipitation to solve the problem of agriculture water. At the same time, uneven precipitation would also aggravate drought trend in some places in Hexi. From the long-term trend, the precipitation uniformity degree in space and time still show large fluctuation, which may lead to some natural disasters, such as drought, sand storm and extreme climate.