The impact of urbanization on the surface temperature in Lanzhou during the period of 1951–2010

Based on the observational data in Lanzhou and two other sites surrounding it from 1951 to 2010, this paper analyzes the surface air temperature changes of Lanzhou and its surrounding sites during the past 60 years by the surface air temperature Linear trends and the surface air temperature trend coefficient; this paper also study the changes of urbanization in Lanzhou by the changes of the population in Lanzhou for the past 60 years. We found that there is a close relation between surface air temperature change and urbanization development. There are distinct seasonal differences in effects of urbanization on surface air temperature change trend, and different effects of urban heat island are observed in different time periods. After 1984, the average surface air temperature trend coefficient of Lanzhou was more obvious than those of the surrounding sites; the changes trend is bigger than the value of before 1984, which indicating that the urban heat island effect increases with the increase of both the surface air temperature and the warming rate. We also found that the heat island effect of Lanzhou vary according to the season and month, the most significant warming trend occurs at all the three sites in spring, sequentially followed by spring, autumn and summer. Urbanization of Lanzhou had greater effect on the maximum surface air temperatures than on the minimum. The surface air temperature trend coefficient of the former is larger than the latter and the surface air temperature increasing trend becomes bigger after 1975.