Study On The Influence Of Urban Geometric Form Factors On The Heat Island Effect In Guangzhou

Urban planning has a huge impact on the local microclimate,which in turn affects the comfort and environmental quality of the city.Urban open space plays an important role in changing urban climate.The geometric form factor of a city is composed of height width ratio(H/ W),sky view factor(SVF)and the direction defined by the long axis of the street.This has a direct impact on the incidence of solar radiation,absorption and emission of long wave radiation,and has a significant impact on the temperature change of streets and surrounding environment.In this paper,the representative hot island area and cold island area streets in Guangzhou are selected as the research objects.According to the different urban geometric shape factors that affect the microclimate of streets,based on the principle of controlling variables and covering as wide as possible,select typical measuring points and comparative measuring points,monitor the temperature of each measuring point in real time,and collect the urban geometric shape data to analyze the relationship between temperature and urban geometric shape factors.First of all,the intensity and range distribution map of Guangzhou heat island in summer in2014-2017 city heat island Monitoring Bulletin issued by Guangzhou climate and agricultural meteorological center is used to find out the intersection area with high intensity of heat island within 4 years by two-dimensional image superposition,which is taken as the measurement object area.This method can effectively eliminate the random influence of heat island intensity calculation in different years with different climate,eliminate the uncertain factors such as weather,calculation and measurement error,and lock the area that becomes heat island due to urban objective factors,so as to further analyze the causes of heat island effect.Secondly,select a number of measuring points in each heat island area of Guangzhou City,and measure the real-time temperature of the measuring points in the heat island area compared with the adjacent non heat island area as the data support.At the same time,it is necessary to record the geometric shape factor of each selected measurement point as an independent variable for comparison.Through the analysis of urban geometric form factor and corresponding temperature,why the temperature difference between two groups of observation points in the same area is large,find out the mechanism of urban geometric factor,and further get the impact of urban geometric form factor on heat island effect.Finally,the temperature data of the measured points and the comparison points are analyzedto find out the correlation degree between the temperature and the urban geometric factors.The preliminary results show that the geometry of the city plays an important role in the mitigation of the urban heat island.The measuring points with smaller sky view factor and larger height width ratio(H / W)have a relatively cold environment,and the temperature of each measuring point is highly related to the size of SVF.In addition,the direction defined by the long axis of the valley will also affect the solar radiation equivalent of the street pavement,and the reclamation open land is also easy to become the area where the heat island gathers.