Research On The Correlation Characteristics Of Wind And Thermal Environment In Urban Built-up Spaces Based On Local Climate Zone

The compact urban construction model leads to a high degree of mixing of land use functions in the underlying space,frequent local climate problems in the built-up space,and widespread attention paid to the study of wind thermal environmental adaptability.Considering the heterogeneity of spatial morphology and revealing the characteristics of wind speed and direction heterogeneity at local scales,as well as their correlation with the thermal environment,is currently an urgent issue to be addressed.This study takes Wuhan City as an example and classifies built-up spaces based on Local Climate Zone(LCZ).Using 2019 wind speed,wind direction,and temperature monitoring data from urban meteorological stations,it reveals the heterogeneity of local wind speed,wind direction,and wind direction in built-up spaces of different types of cities,and discusses the differences in wind thermal environmental correlation relationships influenced by local wind direction.The main conclusions are as follows:(1)There are stable wind speed heterogeneity patterns and strong wind direction heterogeneity among different types of built-up spaces.Different types of built-up spaces exhibit the characteristics of Large low-rise(LCZ8)>Sparsely built(LCZ9)>Open lowrise(LCZ6)>Open midrise(LCZ5)>Open high-rise(LCZ4)>Compact midrise(LCZ2)>Compact low-rise(LCZ3)in average wind speed,and maintain stability under different background wind speeds.The ventilation in the Compact low-rise is the most congested,with an annual average wind speed of 0.24 m/s,which is only 1/8 of the annual average wind speed of Large low-rise.Except for the Compact low-rise where the annual calm wind frequency is as high as 72%,the annual calm wind frequency of other types of built-up spaces ranges from 11% to 40%,and all types of built-up spaces are concentrated between 19:00 at night and 6:00 the next day.There is strong heterogeneity in the local wind direction under the same type of built-up space,and it may be influenced by the internal architectural form and surrounding built environment of LCZ.However,the average wind speed in the dominant wind direction of all built-up space types still follows the law of LCZ inter class wind speed.(2)There is a certain correlation between local wind speed and temperature in summer under different types of built-up spaces.There is a certain wind speed threshold for the impact of summer daily wind speed on daily temperature under all types of builtup spaces.Beyond this wind speed threshold,there is a negative correlation between daily wind speed and daily temperature,and vice versa,there is a positive correlation.The daily average wind speed thresholds for LCZ2,LCZ3,LCZ4,LCZ5,LCZ6,LCZ8,and LCZ9 are 0.55 m/s,0.18 m/s,0.76 m/s,0.87 m/s,1.08 m/s,1.58 m/s,and 0.92 m/s,respectively.The correlation between summer wind and heat in different types of built-up spaces is influenced by local wind direction.There is an open space enclosed by high-rise or midrise buildings in the wind direction of the authorities,and the ventilation of the plot can alleviate local high temperatures to a certain extent;When there is an open space enclosed by a group of low-rise buildings in the wind direction of the authorities,or when the local wind direction is parallel to the direction of corridors such as streets,the cooling effect of the ventilation of the plot should be judged based on the thermal characteristics of adjacent LCZ plots in the local wind direction;The wind direction of the authorities is densely packed with trees and building blocks,and ventilation of the plot may cause local warming.It is necessary to consider the adaptive design of urban wind thermal environment based on local wind direction characteristics.Based on the research results of the ventilation situation of different types of built-up spaces and the differences in the impact of local wind direction on summer ventilation and cooling,taking into account the characteristics of the LCZ plot’s building environment,green coverage,etc.,wind thermal environment optimization strategies are proposed for different types of built-up spaces in cities,providing reference for urban design to achieve climate adaptation.