Abstract
Abstract. A new multi-scale model of urban air pollution is presented. This model combines a chemistry–transport model (CTM) that includes a comprehensive treatment of atmospheric chemistry and transport on spatial scales down to 1 km and a street-network model that describes the atmospheric concentrations of pollutants in an urban street network. The street-network model is the Model of Urban Network of Intersecting Canyons and Highways (MUNICH), which consists of two main components: a street-canyon component and a street-intersection component. MUNICH is coupled to the Polair3D CTM of the Polyphemus air quality modeling platform to constitute the Street-in-Grid (SinG) model. MUNICH is used to simulate the concentrations of the chemical species in the urban canopy, which is located in the lowest layer of Polair3D, and the simulation of pollutant concentrations above rooftops is performed with Polair3D. Interactions between MUNICH and Polair3D occur at roof level and depend on a vertical mass transfer coefficient that is a function of atmospheric turbulence. SinG is used to simulate the concentrations of nitrogen oxides (NOx) and ozone (O3) in a Paris suburb. Simulated concentrations are compared to NOx concentrations measured at two monitoring stations within a street canyon. SinG shows better performance than MUNICH for nitrogen dioxide (NO2) concentrations. However, both SinG and MUNICH underestimate NOx. For the case study considered, the model performance for NOx concentrations is not sensitive to using a complex chemistry model in MUNICH and the Leighton NO–NO2–O3 set of reactions is sufficient.
Highlights
IntroductionThe first urban air quality model with spatial and temporal resolution was developed for the Los Angeles basin in California, USA (Reynolds et al, 1973)
Urban air pollution has been a public health issue for many decades
MUNICH computes the mass fluxes between the urban canopy and the urban atmosphere above roof level and the SinG interface transfers them to Polair3D to compute new air pollutant concentrations in the grid cells above the urban canopy
Summary
The first urban air quality model with spatial and temporal resolution was developed for the Los Angeles basin in California, USA (Reynolds et al, 1973). This three-dimensional (3-D) gridded Eulerian model used the atmospheric diffusion (mass-conserving) equation to calculate the change with respect to time of the relevant air pollutant concentrations due to emissions, transport, chemical transformation, and deposition. Mass transfer between the street and the urban background atmosphere at the top of the street (i.e., roof level) is simulated This initial concept has been extended to calculate air pollutant concentrations within a network of streets with the SIRANE model (Soulhac et al, 2011). Some initial applications of MUNICH and the SinG model to a Paris suburb are discussed
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