Enhancing winter urban simulations in the TEB urban climate model

Many cities experience a strong Urban Heat Island (UHI) in winter with early snow melt and decreased snowfall. Urban characteristics, snow cover, and human activities are important contributors to these effects. However, the winter UHI magnitude and its different driver contributions are still unclear and still pose many challenges to model. Urban climate models have demonstrated strong performances to simulate the urban climate. But few studies address the representation of the cold urban climate. Thus, we have enhanced the capabilities of the TEB urban climate model to simulate winter conditions. The model has been upgraded with an ice layer, a multilayer snow model, an explicit representation of the traffic impacts on road temperature and snow characteristics, and a snow cover parameterisation for urban environments. These new processes have then been evaluated in open environments with observations from road weather stations and in urban environments from the Helsinki sites available in the Urban-PLUMBER initiative. The snow depth and the artificial surface temperature are better simulated. In particular, snow-melt episodes have improved drastically. At the Helsinki site, the results show better representations of the energy fluxes in winter and spring. We believe that this work is an important step towards addressing the current limitation for cold urban climate modelling.