Abstract:To alleviate the crisis of urban thermal environment of Nanjing, the Weather Research and Forecasting Model (WRF) was uesd to simulate the effects of three types of roofs (conventional roof, high albedo roof and randomized glass-polymer hybrid metamaterial roof) during the extreme high temperature weather in Nanjing in 1-31 July 2017. The results showed that (1) cooling roofs (like high albedo roof and randomized glass-polymer hybrid metamaterial roof) can reduce the temperature of cities by weakening the solar radiation reaching the surface of the city. During the daytime, the average temperature of randomized glass-polymer hybrid metamaterial roof drops by 0.8-1.2℃, and the average temperature decreases 0.2-0.4℃ in the nighttime. The average temperature of the high albedol roof drops by 0.6-0.8℃ during the day and decreases 0.2℃ at night. (2) The surface temperature index can be used to characterize the thermal performance of the cooling roof. The surface temperature index of the randomized glass-polymer hybrid metamaterial roof is 0.16-0.43. The surface temperature index of the high albedo roof is 0.05-0.26, indicating that the cooling effect of the randomized glass-polymer hybrid metamaterial roof is stronger than the high albedo roof. (3) The high albedo roof and the randomized glass-polymer hybrid metamaterial roof can return 36.7% and 47.1% of the solar short-wave radiation respectively. The atmosphere absorbs heat 19.6% less and 34.8% less than conventional roof.