Influence Of Ventilation On The Heat Island Effect Of Urban Agglomeration In The Context Of Local Climate Zone

Global warming is drawing more and more attention from human beings.It not only affects the ecological environment of the earth,but also is accompanied by a series of urban problems.Therefore,the use of natural conditions to mitigate the urban heat island effect is particularly important for urban future planning and urban sustainable development.This paper selects some cities in Beijing-Tianjin-Hebei as research areas,based on building 3D data,meteorological data and multi-source remote sensing data.Local climate zone classification,GIS program design and land surface temperature inversion are used.Using the perspective of the local climate zone to quantitatively evaluation the urban ventilation,study the differences in the frontal area index of buildings in the local climate zone,the urban ventilation in different seasons and the impact of urban ventilation on the heat island effect.Analyze other factors that affect urban heat islands and the contribution of urban ventilation to alleviate urban heat islands.The main conclusions are as follows:?1?Local climate zones in urban agglomerations are complex.The coverage of building types in large cities is more complex than that of natural types,while small cities have more natural coverage than buildings.The local climate zone can reflect the surface coverage of the city.In a single city,the proportion of the building type LCZ is Beijing > Tianjin > Shijiazhuang > Baoding > Tangshan > Langfang > Cangzhou > Qinhuangdao.The center of each urban building group is LCZ3 and LCZ4.The surrounding area of the building group is LCZ6.The natural type is determined by urban construction and terrain.The northern area is the most LCZA,and the southern area is mostly LCZE.Among the LCZs in the study area,the LCZ proportions are LCZ6 > LCZ5 > LCZ3 > LCZ2 > LCZ4 > LCZ1,and in the natural type LCZ,LCZE > LCZA > LCZD > LCZF > LCZC > LCZB.In each local climatic zone,Beijing has the largest proportion in the building type,while the natural type is Baoding,Cangzhou,and Qinhuangdao.The city is gradually developing,and the trend of building types in small cities is LCZ2 and LCZ5.?2?Seasonal changes have little effect on the FAI value.The average FAI value shows a trend of Beijing > Tianjin > Shijiazhuang > Cangzhou > Langfang > Tangshan > Baoding > Qinhuangdao.Therefore,Beijing has the greatest degree of obstacles to the wind,and Qinhuangdao has the smallest.In terms of spatial distribution,the FAI of each city starts from the center and gradually spreads out in a concentric circle.The buildings in the center of the urban building block the wind from being blocked.The wind can be blocked by the buildings,resulting in a large FAI value.The peripheral FAI has the lowest value.The maximum FAI is in Beijing and the minimum is in Tangshan.The LCZ ventilation of different building types is different.The research found that the urban FAI value is mainly determined by the building height,density and prevailing urban wind.As the average building height and building density decrease,the FAI value also gradually decreases.The correlation between the average height of buildings in winter and FAI reaches 0.738 ^**,0.747 ^** in summer,the correlation between building density and FAI in winter is 0.260 ^**,and 0.257 ^** in summer,FAI is positively correlated with the average height of buildings,and has a low density Degrees are positively correlated.Therefore,in the layout of the building,rationally plan the spatial distribution of the building and use ventilation to alleviate the urban heat island effect.?3?The difference in land surface temperature in summer is greater than in winter.In winter,the land surface temperature is mainly affected by changes in latitude and climatic zones,showing that the land surface temperature in the southern part of the study area is higher than that in the north,while the summer land surface temperature is mainly affected by the surface cover,where the land surface temperature in the building coverage area is significantly higher than vegetation and water Covered area.If the regional building coverage is densely distributed,the land surface temperature and high temperature areas are concentrated in this area.If the buildings are distributed in a mesh cluster,the land surface temperature and high temperature area is consistent with the building coverage space distribution.In winter,the highest LST is 17.79 ?,and the lowest is-17.10 ?.In summer,the highest LST reaches 51.98 ?,and the lowest LST is 16.46 ?.?4?Multi-regression coupling analysis of urban form and urban ventilation and land surface temperature can be seen that land surface temperature is closely related to building density,floor area ratio,average height,vegetation coverage and building windward area index.In winter,it can be seen that the influence degree of the index factor on the land surface temperature is: vegetation coverage> floor area ratio > FAI> average height> building density,and the influence degree of the summer index factor on the land surface temperature is: vegetation coverage> building density> FAI > floor area ratio > Building height.By analyzing the correlation between FAI and land surface temperature,the degree of influence of urban ventilation on the heat island effect is determined.The correlation between winter FAI and land surface temperature is 0.066 ^**,and the correlation between summer FAI and land surface temperature is 0.304 ^**.The correlation between FAI and LST in Local climate zone of different building types in winter is LCZ1> LCZ2> LCZ3> LCZ6> LCZ4> LCZ5,and in summer,LCZ1> LCZ3 = LCZ6> LCZ4> LCZ2> LCZ5.