Modified RAMS-Urban Canopy Model for Heat Island Simulation in Chongqing, China

A single-layer urban canopy model was integrated into a nonhydrostatic meteorological model, the Regional Atmospheric Modeling System (RAMS). In the new model, called RAMS-Urban Canopy (RAMS-UC), anthropogenic heat emission was also considered. The model can be used to calculate radiation, heat, and water fluxes in an urban area, considering the geometric structure and thermodynamic characteristics of the urban canopy. The urban canopy was represented by normalized street canyons of infinite length, which were bordered by buildings on both sides. The urban region was covered by three types of surfaces: roof, wall, and road. Anthropogenic heat was emitted from these surfaces. Sensitivity tests between the original RAMS and the modified one were carried out by simulating the urban heat island (UHI) of Chongqing, located in an inland mountainous region in China. The results of the model were also compared with the observational data. It was found that the original model could not accurately simulate the UHI, in particular at night, whereas the accuracy was significantly improved in the RAMS-UC. The improvement is substantial even when anthropogenic heat emission is set to zero.