Evaluation of multi-layer urban canopy model (MLUCM) for urban microclimate predictions at different urban contexts

Modeling tools are often used to obtain a better understanding of the characteristics of urban microclimates. Among the different approaches to physics-based modeling, urban canopy models tend to be computationally faster than computational fluid dynamics (CFD) simulations. However, the evaluation of current urban canopy models for different urban characteristics is still limited, especially for wind speed. This study aims to evaluate the potential usability of the existing urban canopy model for microclimate variable prediction in different urban contexts, specifically the vertical city weather generator (VCWG) v1.4.5, which can predict microclimate variables at different vertical heights. The measurement data used in model evaluation were obtained from 248 weather stations in Seoul, Republic of Korea. The results showed that among the input parameters, a few variables had significant impact on the wind speed prediction results, namely, the turbulent coefficient during unstable conditions, the pressure gradient coefficient, and the aerodynamic roughness length. The discrepancy in wind-speed prediction tended to be lower during the summer season, with lower wind speeds at the rural weather station. Further investigations also addressed the significant parameters of wind speed prediction related to the calculation of the turbulent diffusion coefficient and pressure gradient.