여름철 인간 열환경지수에 미치는 가로수와 단독수의 영향 분석

Abstract

In order to analyze the effect of street trees and single trees on human thermal sensation (thermal comfort) in summer, microclimatic data were measured and analyzed at sunny and shaded locations of two deciduous broadleaf and three broadleaf evergreen species of street trees and one deciduous broadleaf, two broadleaf and one conifer evergreen species of single trees. As a result, the mean differences by species in air temperature, relative humidity and wind speed were small: 0.2-1.5 ℃, 0.9-5.3 % and 0.1-0.5 ms⁻¹ for street trees and 0.1-0.5 ℃, 0.5-1.8 % and 0.0-0.7 ms⁻¹ for single trees, respectively. However, the mean difference in the mean radiant temperature was great: 27.1 ℃ for street trees and 17.8 ℃ for single trees. In the results of physiological equivalent temperature (PET) and universal thermal climate index (UTCI), which are human thermal sensation (thermal comfort) indexes, the shaded locations by the trees showed mean reduction rates of 21.2-31.3 % in the PET for street trees and 14.8-20.5 % for single trees compared with the sunny location, which are equivalent to 1.5-2.5 levels of thermal perception for street trees and 1.0-1.5 levels for single trees. Also, 12.7-20.0 % for street trees and 9.2-12.5 % for single trees in the UTCI were reduced by the trees' shadows, which is equivalent to 1.0-1.5 levels of heat stress for street trees and 0.6-0.8 levels for single trees. In addition, although the broadleaf evergreen trees in the street trees had 5 % greater mean reduction in PET than that of the deciduous broadleaf trees, the Zelkova serrata that belonged to the deciduous broadleaf trees showed the equivalent thermal reduction effect as the broadleaf evergreen trees because of the high density of branches and leaves. In the single trees, the conifer evergreen tree had 3.6% and 1.9 % greater mean deduction in PET than those of the deciduous broadleaf tree and the broadleaf evergreen trees, respectively. Moreover, one of the broadleaf evergreen trees, Machilus thunbergii which had a dense crown, produced the same thermal reduction effect as the conifer evergreen tree. Therefore, the mean radiant temperature and the density of the crown (branches and leaves) were the main influences in thermal modification by these street and single trees in summer.