Modeling Urban Climate for Built Environment Studies, an Inter-Comparison of Three Local Scale Models

There are a limited number of models that can reproduce the climate impact of urban heat mitigation measures in and around buildings for an extended period of time. Even fewer models are accessible to professionals working with the built environment. However, the data these models can deliver are at the core of urban and building microclimate studies such as outdoor thermal comfort and indoor overheating evaluations. As nature-based solution play an important role in current heat mitigation practices, the aim of this work is to evaluate the performance of three accessible models in their ability to reproduce the effect of vegetation in urban environments.

The evaluated models are the Urban Weather Generator (UWG), the Surface Urban Energy and Water Balance Scheme (SUEWS) and the Vertical City Weather Generator (VCWG). Each of them exhibits increasing complexity in terms of street tree integration. UWG, a single-layer model, relies on a relatively simple parametrization. SUEWS's multi-layer canopy model combines simple parametrization for sensible and latent heat fluxes with a novel approach that computes the 3D interaction of shortwave and longwave radiation with complex surface canopies (implemented via the SPARTACUS module). Finally, the multi-layer scheme of VCWG considers both the aerodynamic and thermal effects of urban elements and trees with the urban canopy. This inter-model comparison builds on urban weather stations data from the cities of Novi Sad, Serbia and Toulouse, France.