A three-dimensional urban canopy model for mesoscale atmospheric simulations and its comparison with a two-dimensional urban canopy model in an idealized case

Most urban canopy models adopt the two-dimensional (infinitely long) street canyon as the basic unit to represent the city texture. This paper presents a new urban canopy model, the 3DUCM (three-dimensional urban canopy model), which accounts for every single building of the city to determine the air temperature and heat fluxes involved in the surface energy budget. 3DUCM has been coupled with the Colorado State University Mesoscale Model, and an idealized city has been considered as case study. Among the main results, it is shown that the air temperature simulated by 3DUCM within the canopy is lower compared to that calculated using the two-dimensional approach, mainly because of crossroads modelling. The new model is suitable for predicting the temperature field down to the building scale and it is potentially easy to apply to realistic scenarios, for which the actual shape, orientation and constructing material properties of every single building constituting the canopy can be taken into account.