Observational analysis on the mitigating effects of different greenings on thermal environment in Nanjing

Greenings had been considered as potential measure in mitigating the urban thermal environment conditions. In this paper, three types of urban land including asphalt road under the sun, grassland under the sun, asphalt road under the shade of adult Indus-tree were selected to measure the air temperature (1.5m height) and land surface temperature, the role of different type of urban greenings in moderating the thermal environment were compared. The results showed that adult Indus-tree had distinct cooling effect during the day and had insulating effect at night, that grassland had cooling effect in the day, but the cooling capacity was lower than that of adult Indus-tree during the day for the thermal environment at 1.5m height. For the surface thermal environment, the role of decreasing temperature of adult Indus-tree was higher than that of grassland during the day, It was inverse at night, and the land surface temperature of asphalt road under the shade of adult Indus-tree was higher than that of asphalt road under the sun in the day except 1~2 hours in the early morning; the land surface temperature of grassland is obviously lower than asphalt road under the sun at night, and intensity was stronger than that of the shade of adult Indus-tree .