The urban heat island in Nanjing

By using air temperature data of four meteorological stations from 1961 to 2005, the urban heat island (UHI) effect of Nanjing was comprehensively investigated. The conclusion can be drawn as follows: In general, the UHI intensity of Nanjing is about 0.5 °C, with a high-value intensity found when the lowest temperature appears during the night, reaching approximately 6 °C in extreme cases. The UHI effect in Nanjing has obvious seasonal and daily change characteristics. The UHI intensity of summer is higher than that of winter and that in nighttime is higher than that in daytime. Along with urban scale development, the UHI intensity of Nanjing is increasing. Its increase rate is 0.109 °C/10 a, calculated by annual mean air temperatures. The UHI phenomena mainly occurred from the 1980s to the 1990s, especially in the 1990s, which was related to the rapid urbanization period in China. The UHI intensity slightly declined after 2000, which was in correlation with the green land increase in Nanjing.