PALM Traffic module

Abstract

ZÁKLADNÍ ÚDAJE: PMC26 Book of Abstracts. Hannover: Leibniz University Hannover, German Weather Service, 2026. s. 15-16. [PMC 26: PALM Model Conference. 23.02.2026-26.02.2026, Hannover]. ABSTRAKT: The air quality in street canyons significantly affects citizens’ well-being. It is strongly dependent on local transportation emissions and on canyon ventilation, which is influenced by street canyon characteristics, including e.g. the presence of trees. A reliable model capable of assessing air quality at this level of detail is needed for efficient urban planning. The PALM model can simulate air quality at this scale; however, strong overestimations of concentrations were observed under certain meteorological conditions, raising questions about the reliability of all simulations. The missing representation of the influence of local vehicle traffic on the street canyon air flow and temperature was identified as one of the reasons for this model behaviour. The new PALM Traffic module provides a simple, parameterised way to include these processes. Based on traffic flow characteristics, it calculates the induced forces and adds them to the model dynamics as additional airflow tendencies. It also consider the heat produced by vehicles and transforms it into additional tendencies of air potential temperature. The module is not intended for detailed simulation of individual vehicles, but rather for including the missing processes in street canyon ventilation simulations. Test simulations show a significant influence of these added processes on street canyon ventilation and air quality under stable meteorological conditions, while the impact in other situations is moderate. We expect further improvements and extensions of the module in future versions based on gathered experience.