Development of a 3D urban canopy model for evaluating cooling effect of urban green space.

Urbanization is progressing around the world and the phenomenon of urban heat islands, where the temperature of cities increases compared to the surrounding areas due to climate change, is intensifying. Many strategies are being applied to alleviate urban heat islands, and one of them is urban greening. Urban green areas form shadows to block solar radiation, or change the rate of reflection and emission of heat caused by changes in surface environment. It also has the effect of reducing the surface temperature by increasing latent heat through the evapotranspiration occurring in the leaves. Representative urban greening strategies are street trees, green roof, and green wall. Since the cooling effect varies greatly depending on the weather environment, size of green space, and location, it is challenging to estimate the cooling effect that changes according to various environments. In this study, a three-dimensional urban canopy model was developed to evaluate the effects of various green space. This model, which simulates the copy transfer process between urban elements, first builds a domain consisting of squares of a certain size and calculates the view factor and the sky view factor. Next, the short-wave radiantion and the long-wave radiantion are simulated to calculate the net radiation. Finally, the net radiantion is partitioned into sensible heat, latent heat, and storage heat. This model can be used for efficient green space planning to reduce urban heat.