Study On The Relationship Between Urban Form And Urban Heat Island Based On Local Climate Zoning

With the acceleration of urbanization,the problem of urban heat island effect is becoming more and more serious.The increase of urban temperature not only leads to the deterioration of urban thermal environment,but also accompanied by the frequent occurrence of extreme weather events,affecting social development and residents'health.In the past studies on urban heat island intensity,the commonly used method is to calculate the urban heat island intensity by using the temperature difference between urban and rural areas,but it cannot fully reflect the differences in the thermal environment within urban areas.Therefore,it is of great significance for urban planning and construction to explore the relationship between urban form and urban heat island intensity.Firstly,based on the theory of local climate zoning,this study studied the relationship between urban form and urban heat island intensity by conducting long-term outdoor thermal environment observation experiments.Firstly,based on the LCZ theoretical system,several LCZ plots in Guangzhou were selected preliminarily by means of satellite images and field research.The open source three-dimensional urban spatial data and numerical simulation methods were used to calculate the morphological characteristic parameters of each zone,and the selected LCZ land type was determined.In the end,9 representative LCZ zones(7built environments and 2 natural environments)were selected as the research objects.In each LCZ region,two fixed observation points are arranged within 100m from the center to carry out long-term(2019.7.12?2020.7.11),high-density continuous temperature observation experiments.Secondly,through the correlation analysis between the suburban daily temperature range(DTR)and the maximum urban heat island intensity(UHI_max),it is preliminarily proposed that DTR?10?should be used as the threshold value to identify the meteorological conditions conducive to the development of Guangzhou urban heat island,which provides a preliminary method for selecting the typical meteorological days suitable for the development of Guangzhou urban heat island.And analyzes the typical weather strips and different spatial and temporal distribution of heat island intensity LCZ partition,the results show that different types of heat island intensity in LCZ partition exists obvious difference,especially at night,is characterized by compact construction area(LCZ1,2,3)>open buildings(LCZ4,5)>large low-rise buildings(LCZ8),LCZA appear obvious cold island phenomenon,3?5 hours after sunset peak.The average heat island intensity of LCZ plots was significantly different at night,and there was a positive correlation between building density and heat island intensity,but the difference was small in the daytime.The diurnal variation of heat island intensity is consistent with that of heating and cooling rate.Finally,the relationship between the characteristics of urban morphology and the Japanese maximum urban heat island is analyzed by using the urban temperature observation data of Guangzhou,and the applicability of a diagnostic equation for the intensity of the maximum urban heat island is tested.Based on the LCZ theoretical system and the thermal environment experiment of urban local zoning,the daily maximum urban heat island intensity of six LCZ zoning regions was analyzed.The measured results of 39 days with fine weather,weak wind and little cloud were selected to evaluate the diagnostic equation,and the results showed that the diagnostic performance of the equation was(R²=0.66,RMSE=1.69,MEAE=1.40).Compared with the test results of the equation in Europe(R²=0.65,RMSE=0.91K,MEAE=0.58K)and Nanjing(R²=0.46,RMSE=1.08K,MEAE=0.76K),the results show that the correlation of the equation is higher than that in Nanjing,but the data fluctuates greatly,and the diagnostic accuracy needs to be improved.Therefore,based on the current data,a diagnostic equation(R²=0.46,RMSE=0.93,MEAE=0.83)is proposed,which can be used to predict the daily maximum urban heat island intensity in hot and humid areas,providing a certain reference value for the prediction of urban heat island in hot and humid areas.