Spatial Characteristics of Small Green Spaces' Mitigating Effects on Microscopic Urban Heat Islands

Abstract:

The purpose of the study is to find small greens’ disposition, types and sizes to reduce air temperature effectively in urban blocks. The research sites were six high developed blocks in Seoul, Korea. Air temperature was measured with mobile loggers in clear daytime during summer, from August to September, at screen level. Also the measurement repeated over three times a day during three days by walking and circulating around the experimental blocks and the control blocks at the same time. By analyzing spatial characteristics, the averaged air temperatures were classified with three spaces, sunny spaces, building-shaded spaces and small green spaces by using Kruskal-Wallis Test; and small green spaces in 6 blocks were classified into their outward forms, polygonal or linear and single or mixed. The polygonal and mixed types of small green spaces mitigated averaged air temperature of each block which they belonged with a simple linear regression model with adjusted R² = 0.90**. As the area and volume of these types increased, the effect of air temperature reduction (ΔT; Air temperature difference between sunny space and green space in a block) also increased in a linear relationship. The experimental range of this research is 100m² ~ 2,000m² of area, and 1,000m³ ~ 10,000m³ of volume of small green space. As a result, more than 300m² and 2,300m³ of polygonal green spaces with mixed vegetation is required to lower 1°C; 650m² and 5,000m³ of them to lower 2°C; about 2,000m² and about 10,000m³ of them to lower 4°C air temperature reduction in an urban block.