The impact of urbanization on air temperature across China

Based on daily mean air temperature, maximum air temperature and minimum air temperature data from 1961 to 2000, the annual and seasonal evolution as well as the spatial distribution of the warming effect caused by the urbanization in China are investigated. One hundred and ninety one urban meteorological stations were categorized into three classes according to the urban population. A positive correlation between urban population and the rate of urban warming was found. Our results also suggested that the urban-rural difference in term of minimum temperature, with the strongest urban heat island (UHI) effect reaching 0.74 K in winter over large city station pairs, showed good ability to capture the UHI effect. The impact of urbanization on air temperature displayed sharp changes since the innovation and opening of China in 1978. The cities with strong UHI effects were mainly located in regions with rapid industrial and the economic development. Cities in the north of China showed a stronger UHI effect than those in the south. The UHI effects were relatively weaker in coastal cities than in inland ones in spring and summer, with the reverses found for autumn and winter. Furthermore, North China showed greater coastal-inland UHI differences than South China in a given season.