Study On The Landscape Design Strategy Of University Square In Hot-humid Areas Based On Thermal Comfort

Hot-humid areas has high temperatures and humidity weather in summer,causing people thermal discomfort in outdoors spaces.Properly utilizing landscape elements can regulate the outdoor thermal environment and mitigate the urban heat island effect.The types and layouts of landscape elements can affect outdoor shading,wind environment,and the distribution of outdoor thermal sensations,significantly.This study explores the effect of landscape elements(trees,pavement,water bodies)on the outdoor thermal environment of a university square spaces under typical summer and winter weather in a hot-humid areas in China.Evaluating the outdoor thermal comfort,by PET(Physiological Equivalent Temperature).Through field measurement and ENVI-met model simulation,the thermal effect of different landscape elements and their combinations on the outdoor environment was evaluated.The results indicate that:(1)Water bodies have the strongest cooling ability in summer,but bring cold discomfort in winter.Placing trees around water bodies can increase the PET value by up to 3.8 ℃ in winter.(2)Trees can reduce excessive solar radiation in summer and cold winds in winter.Combining landscape elements,can further reduce PET by 1.5 ℃ in summer and increase by up to 0.7 ℃ in winter.(3)Comparing with low LAI trees,high LAI trees have a stronger ability to regulate the outdoor thermal environment in winter and summer.(4)The change of pavement materials’ albedo has less effect on outdoor thermal environment,especially when the square covered with rich landscape elements.However,without shading,when the pavement materials’ albedo is higher than 0.3 it may have negative thermal effects on the outdoor open space.(5)The trees’ planting distance has a impact on the outdoor thermal environment.The maximum PET difference in the activity space was 1.14 ℃ and 2.13 ℃ in summer and winter,respectively,when the trees were arranged at different planting distances.However,there is no positive relationship between their planting distance(quantity)and the ability to improve the thermal environment.When the planting distance was adjusted from "2" to "1.5" and from "1.5" to "1",the number of trees increases by 14 and 20,respectively,and the PET difference is 0.9 and 0.24 ℃,respectively.(6)Whether the non-activity space in the campus square is full of trees or not has essentially the same effect on the thermal environment of its surrounding active space.(7)The arrangement of trees reduced the PET values of the activity space both in summer and winter.However,with planting trees in winter,the PET value of the activity space remained acceptable(>11.3 ℃)during most of the daytime,and more comfortable at night compared to treeless conditions.Therefore,trees’ arrangement is beneficial in summer,while harmless in winter.Based on the above results,this study proposes the optimization design strategies for different university campus squares types.Those finding can provide design references for urban planners and landscape designers for creating comfortable university square spaces,in order to alleviate high temperatures on campus and improve the quality of university square spaces in hot-humid areas of China.