Parameterizing the aerodynamic effect of trees in street canyons for the street network model MUNICH using the CFD model Code_Saturne

Abstract. Trees provide many ecosystem services in cities such as urban heat island reduction, water runoff limitation, and carbon storage. However, the presence of trees street canyons reduces wind velocity limits pollutant dispersion. Thus, to obtain accurate simulations concentrations, aerodynamic effect should be taken into account air quality models at level. The Model Urban Network Intersecting Canyons Highways (MUNICH) simulates concentrations a network, considering dispersion physico-chemical processes. It can coupled regional-scale chemical transport model simulate over districts or cities. tree crown is parameterized here through its impact on average direction vertical transfer coefficient associated with tracer. parameterization built using local-scale performed computational fluid dynamics (CFDs) code Code_Saturne. two-dimensional CFD an infinite canyon are used quantify trees, depending characteristics (leaf area index, volume fraction, height ratio) drag porosity approach. slows down flow produces turbulent kinetic energy street, thus impacting tracer This increases leaf index fraction horizontal reduced by up 68 %, while 23 % here. A these effects transfers for MUNICH proposed. Existing parameterizations modified based Code_Saturne both building transfers. similar (quantified relative deviation between cases without trees) MUNICH. profile mixing length depend radius, ratio. interaction aspect ratio also considered.