Research On Thermal Environment Characteristics Of Green Roof In Beijing Based On Monitoring Temperature And ENVI-met Climate Simulation

With the rapid development of urban areas,the urban population has increased sharply,and urban ecological problems have also increased,especially in urban heat islands.Increasing urban vegetation coverage is one of the important measures to alleviate the urban heat island effect.However,the construction land in the city is scarce,and the roof of urban buildings becomes an important space for urban greening in the future.It is practical to study the thermal environment characteristics of urban green roofs.This paper classifies and counts 113 existing green roofs in Beijing's Sixth Ring Road,and analyzes the spatial distribution of 113 green roofs in Beijing's Sixth Ring Road using Beijing remote sensing images as data sources.Different types of green roofs were selected as research objects in areas with dense green roof construction and areas with high surface temperatures.We use a thermal infrared imager for temperature monitoring to analyze the thermal environment characteristics of different types of green roofs.However,monitoring temperature has defects on both time and space scales,so we also need to use the ENVI-met software to simulate the thermal environment of the study area.During the simulation,three simulation schemes were set for the green roof study areas: green roof + bare roof,bare roof + bare roof,green roof + green roof.Analysis of thermal environment characteristics of green roof based on these three simulation schemes.The following conclusions are obtained through analysis.(1)Most of the green roofs in Beijing are distributed in areas where the surface temperature is above 40 ? and the urbanization process is relatively fast,and the types of green roofs are mostly garden-style.Whether it is a garden-style green roof or a turfstyle green roof,most of the building's functional types are community public service buildings and commercial buildings.(2)The temperature of the landscape on the green roof is related to its own area,perimeter,type of cover,and proportion of the length of the adjacent green landscape.The research shows that the temperature of the green area with a large proportion of the length of the adjacent green space landscape is relatively low,and the temperature of the shrub is less than the temperature of the grass.If the shrubs and grasses are shaded by trees and can be effectively cooled,the garden-style green roofs of the shrubs and grasses need to consider the vertical structure.(3)Using ENVI-met to simulate the three scenarios of the study area,the temperature maps of the three schemes were obtained.Comparing the temperature difference between the green roof and the simulated bare roof,the temperature of the turf-type green roof is 0.12 ? lower than the temperature of the bare roof,and the temperature of the garden-style green roof is 0.02 ? lower than the temperature of the bare roof.Comparing the temperature difference between the periphery of the green roof and the periphery of the simulated bare roof,it is known that the turf-type green roof can bring about a cooling effect of 0.02 ?,and the garden-type green roof can bring about a cooling effect of 0.04 ?.