An Original Standalone Urban Canopy Model to Support Urban Design/Retrofit Optimization

Standalone Urban Canopy Models (UCMs) attempt to replace the full-fledged atmospheric representation with a computationally light equivalent. The UCM used in this study focuses on the overall exchange of heat, momentum, and moisture with the first level of the atmosphere right above the urban canopy. This enables us, in an urban design/retrofit context, to conduct year-long simulations rela-tively quickly and to assess multiple design alternatives in terms of their impact on urban heat island, outdoor thermal comfort and/or buildings energy demand. To force the UCM at the top boundary of the domain, we investigate two approaches in this study: (1) year-long hourly measurements collected at a nearby rural weather station inform a single-layer urban boundary layer model immediately atop the UCM using a highly original and accurate mechanism of action that differs from the state of the art; (2) direct forcing of the top boundary of the UCM by year-long hourly atmospheric data provided by the ERA5 time series for the location of interest. Furthermore, the urban domain can be divided into multiple categories, each having different morphologies and thermo-physical properties. The result is a computation-ally light numerical model of the urban canopy air that can be seamlessly incorpo-rated in a design optimization work flow. The model is applied to the city of Abu Dhabi (United Arab Emirates). For both boundary conditions, the model’s accuracy is validated against measurements.