Study On Urban Outdoor Thermal Environment And Its Main Landscape Driving Factors Based On Local Climate Zone

In this paper,the local climate zone classification system is introduced,and four local climate areas(LCZ 2,LCZ 4,LCZ 5,LCZ 9)in Linan District of Hangzhou were selected as research objects through WUDAPT 0-level process.The influence of the composition and structure of the underlying surface coverage on the urban thermal environment in summer and winter was studied by the field microclimate measurement and thermal comfort index evaluation(WBGT,MRT and PET).Envi-met was used to study the influence of different types of green space layout on the thermal environment of different local climate types(lcz1,lcz2,lcz4,lcz5)in summer,winter in the two periods of 14:00 p.m.and 21:00 p.m.The main conclusions are as follows:1.In the afternoon of summer,the maximum temperature difference between the local climate areas in the city is 1.5?,and the maximum temperature difference at night is 2.3 ?.The local climate areas in the city are evaluated by the WBGT,MRT and PET.LCZ 2 > 9 > 4,LCZ 5 > 4,LCZ 2 > 4 > 9 at night,LCZ 4 > 5 for air temperature and WBGT,LCZ 5 > 4 for MRT and PET.The maximum temperature difference is 1.4 in winter afternoon and 2.6 in night.LCZ 9 > 4,LCZ 2 > 4,LCZ 5 > 4,LCZ 4 > 9,? ?LCZ 5 > 9 at night,except MRT,LCZ 2 > 5 > 4 > 9.2.The relationship between the thermal comfort index and the underlying surface composition is consistent with the temperature.On the one hand,the composition of urban underlying surface can affect the temperature by changing the heat balance.The most influential factor on the temperature was the ratio of pervious surface,increasing the ratio of pervious surface and reducing the ratio of impervious surface and building surface can improve the thermal environment,and the radius scale of the most influential effect is 120m-150 m.On the other hand,the structure of urban underlying surface affects the reception and divergence of thermal radiation.3.Through ENVI-met model simulation,it was verified that model can effectively simulate local climate scale thermal environment scene,and micro climate factors such as green coverage and shade,building layout have certain impact on the internal thermal environment and thermal comfort.A certain amount of green coverage in the residential area has a cooling effect on the thermal environment,but the cooling effect needs to consider the green layout form comprehensively.The shading effect of the building during the day can reduce the surrounding temperature to a certain extent,but the release of heat stored at night would make the temperature rise.The streets between buildings will form a ventilation corridor in summer,and the appropriate increase of building spacing is conducive to improving the thermal environment.4.The results show that in summer afternoon,the thermal comfort of parallel layout was the best,among which lcz4 was the best.In summer night,the thermal comfort of building enclosure was the best.In winter afternoon,the thermal comfort of parallel type and building enclosed type was better,and in winter night,the thermal comfort of parallel type was the best.5.At the same underlying surface ratio,in summer and winter afternoon,no matter in all kinds of LCZs,the temperature difference within the building enclosed green layout was the smallest,and the temperature at night was similar.In the same type of green layout,in summer and winter afternoon,the internal temperature difference of LCZ 1/2 is less than LCZ 4/5 in the three types of green layout;in summer night,the internal temperature difference of LCZ 1/2 is greater than LCZ 4/5 in the three types of green layout;in winter night,the temperature was similar.In the afternoon,the higher the greening ratio,the lower the impervious surface,the lower the building ratio and the greater the temperature difference.At the same underlying surface ratio and the same type of green layout,in the afternoon of summer,the internal temperature difference of LCZ 1 in the three layouts was less than about 0.5-0.6 of ? LCZ 2;the internal temperature difference of LCZ 4 in the three layouts was less than about 0.3-0.4 of ? LCZ 5.At night,the temperature of LCZ 1 and LCZ 2 was similar,and that of LCZ 4 and LCZ5 was similar.In the afternoon,the lower the building height,the greater the air temperature difference.6.Among all kinds of weather factors,wind had the greatest influence on thermal comfort.The results showed that the concept of local climate zone was suitable for the study of urban temperature,which was helpful to predict urban climate systematically and quantitatively.In order to improve the thermal environment of the city,it was necessary to maintain reasonable water penetration ratio,impervious surface ratio and building coverage in urban planning.