Effects of Urbanization on Temperatures over the Qinling Mountains in the Past 50 Years

Based on the normalized temperature datasets of China Meteorological Administration from 1961 to 2012, inter-annual and seasonal varying characteristics of maximum, minimum and mean temperatures over the Qinling Mountains are analyzed.The result shows that average increment of annual average temperature, annual maximum and minimum temperatures in the northern regions are greater than those in southern regions of the Qinling Mountains. The seasonal variation of temperature is different, for average temperature, there is an increase in spring and winter, while the maximum temperature increases obviously in summer, and minimum temperature increases remarkably in winter. There is an obvious increase of diurnal temperature range in spring and autumn while there is a decrease in summer and winter. Mean and maximum temperatures declines remarkably while minimum temperature increasing in summer are the direct cause of summer diurnal temperature range reducing. In order to understand the factor of temperature variation, the DMSP (defense meteorological satellite program)/OLS (operational linescan system) data are used to calculate effects of urbanization and their contributions on air temperature for 5 typical zones. The increase of minimum temperature and average temperature of urban station is found remarkably higher than that of rural station, while the increase of maximum temperature is almost the same. This result shows that effects of urbanization are significant on the increasing of average temperature and minimum temperature. While the variation of maximum temperature is mainly caused by climate change itself. Urbanization development is not at the same pace, the northern part of the Qinling Mountains develops much faster than the southern part. The process of urbanization enhances the warming trend of average and minimum temperature in northern part of the Qinling Mountains, especially in spring and winter. And for the maximum temperature, the process of urbanization weakens the increasing trend in southern part but enhances the warming trend in the northern part. That means the impact of urbanization on temperature may show different characteristics at different climatic zones. The difference of the development of urbanization over the Qinling Mountains enhanced the inhomogeneity of temperature changes.