Influence of the car-induced flow and heat on the street canyon air quality

Abstract

The air quality in street canyons significantly affects citizens’ well-being. It is strongly dependent on local transportation emissions and street-canyon ventilation. This ventilation is affected by street-canyon characteristics, e.g., the presence of trees, and by meteorological conditions and local forcings, including flow and heat produced by moving cars. The microscale meteorological model PALM can simulate air quality at street-canyon scale, and its recently added PALM Traffic module provides a simple, parameterised way to incorporate car-related processes. Based on traffic flow characteristics, it calculates the induced forces and adds them to the model dynamics as additional airflow tendencies. It also considers the heat produced by vehicles and transforms it into additional tendencies of air potential temperature. In this study, we present the influence of car-related processes on street-level pollutant concentrations under different meteorological conditions. We also show that these processes have a significant impact under stable conditions, although their influence is negligible under windy and convective conditions.