Scale impacts of land cover and vegetation corridors on urban thermal behavior in Nanjing, China.

In order to integrate urban microclimatic pattern, heat island intensity, land cover and cooling effect of vegetation corridors in a more comprehensive way, both fixed and mobile observations at two types of scale have been made simultaneously in different weather conditions during hot weather in Nanjing, China. Then the air temperature distribution of Nanjing and its impact factor were detected and quantified, and vegetation cooling models were developed in this paper. There was a significant day-to-day variation of urban heat island (UHI), and the average intensity of UHI during the measurement period was 2.0 °C. The strong UHI usually occurred around midnight; however, a peak UHI was frequently observed 2–3 h after sunset. During daytime, several isolated hot areas were observed next to cooler ones, indicating a negative UHI. The air temperature distributions of the vegetation corridors at mesoscale in the evening were similar to those at micro-scale at noon. The influence of the Purple Mountain was very obvious with the maximum cooling effect up to 3.0 °C/100 m at microscale and 0.4 °C/km at mesoscale. This research indicated that the pattern of the UHI in Nanjing is a function of the climatic conditions, the local topography, the effect of the Purple Mountain and the Yangtze River and the urban characteristics such as land uses, vegetation, building density, traffic loads, construction materials and anthropogenic heat sources, which should be taken into account for urban planning and ecologically comfortable residence. The results have further relevance for environmental implications in a subtropical city on the Yangtze River. [ABSTRACT FROM AUTHOR]