Simulation Analysis Of Thermal Environment Characteristics And Improvement Measures In Wuhan

The rapid development of urbanization has brought serious challenges to the ecological environment and posed certain threats to the physical and mental health of residents.Wuhan is one of the famous ’’Three Furnaces’ ’ due to its hot and humid summer,and it is of great practical significance to study the spatial and temporal variation characteristics of the thermal environment in Wuhan and propose targeted improvement measures to improve the living environment of residents.In this thesis,the hottest period(July 19-22)of Wuhan City in 2018 was selected for analysis and research.In order to obtain a higher resolution of the spatial variation characteristics of the thermal environment in Wuhan,the paper uses a mesoscale regional meteorological model WRF(Weather Research and Forecasting,WRF)coupled with UCM(Urban Canopy Model,UCM)to numerically simulate the thermal environment in Wuhan.A high-precision data of 30 m×30 m is used.And the simulation results of the WRF model are verified by using the 1-hour resolution meteorological data of China Meteorological Administration to prove the feasibility and accuracy of the WRF model simulation.On this basis,the thesis compares the current situation of thermal environment in Wuhan,explores the distribution characteristics of temperature,humidity and wind field in time and space,and further analyzes the spatial and temporal characteristics of thermal environment in Wuhan based on thermal comfort index.Based on the analysis of the current situation,the paper proposes improvement measures for the thermal environment of Wuhan city in three aspects: cooling roofs and green roofs,building morphology and ventilation corridors.The main results obtained from the study are as follows:(1)The model validation results show that the WRF coupled UCM has a relatively good simulation performance for temperature in Wuhan city,with correlation coefficients above 0.93 for all validation points.The simulation performance for relative humidity is slightly worse than that for temperature,with correlation coefficients above 0.82.It can well reflect the real situation of thermal environment in Wuhan city.(2)In terms of time,the trends of daily change curves of 2 m temperature and thermal comfort index are basically the same,but the decline of thermal comfort index at night is much smaller than that of temperature.10 m wind speed at night is dominated by easterly wind with higher wind speed,and there is a large deflection of wind direction during the day,often the high temperature gathering area is accompanied by the deflection of wind direction.Spatially,the high temperature is mainly concentrated in the three main urban areas of Hankou,Wuchang and Hanyang,and the temperature difference between the suburbs at night is large.The spatial distribution of relative humidity is generally "low in the south and high in the north",and the relative humidity difference between the suburbs at night is large.The wind speed in the central urban area is lower than that in the suburbs.The thermal comfort index in the central and northern parts of Wuhan is high.(3)The use of High albedo roofs and green roofs has an improvement effect on the thermal environment of Wuhan.2 m average temperature is reduced by 0.64℃ and 0.70℃respectively,and the best effect is achieved in urban areas during daytime,with a maximum of 2.62℃.Increasing albedo has a better effect on the thermal comfort index in urban areas than in suburban areas,and the effect of green roofs on the thermal comfort index is not obvious.Increasing building height and increasing building width have little effect on 2 m temperature,but they can effectively change wind speed,and the change of wind speed at night is obvious.The effect of building form on relative humidity is relatively weak.(4)The installation of ventilation corridors cools the main urban area significantly,up to 3.0℃.The high humidity aggregation area shifts,and the closer the ventilation corridor is,the greater the change in relative humidity.There is an enhancement of wind speed during the daytime.The thermal comfort index of the urban area is effectively reduced.The improvement effect is correspondingly weakened after the number and width of ventilation corridors are halved.The change of thermal environment caused by the change of land use type from woodland to shrubland is not significant.Based on the above simulation results,the WRF-coupled UCM can better simulate the thermal environment conditions in Wuhan city.Among the thermal environment improvement measures,cooling roofs and green roofs have certain improvement effects.The ventilation corridor has the best effect on the improvement of the thermal environment in the urban area,which can reduce high temperature and high humidity to a greater extent and significantly improve the thermal comfort.