Development of a Multilayer Urban Canopy Model Combined with a Ray Tracing Algorithm

This study introduces a new multiple-layer urban canopy model (MUCM) combined with a ray-tracing algorithm. In the model, we parameterize the urban morphology as an infinite array of identical three-dimensional buildings separated by roads. Heat exchanges are solved for each urban surface at each vertical layer. The ray-tracing scheme is used to explicitly calculate the view factors as well as both the sunlit and shadow fractions of the urban surfaces during the daytime. As a test, we show that this combined MUCM accurately models observations at Kugahara, Tokyo. Thus, the combined MUCM is a new tool for urban climate modelers to more realistically represent radiative processes on urban surfaces. In particular, it may contribute to our understanding of urban climate in the mega-cities of Asia, which generally have high-rise buildings that are more difficult to model with simpler radiative schemes.