Air pollution trapping in the Dresden Basin from gray-zone scale urban modeling

Abstract

Abstract. The microscale variability of urban air pollution is essentially driven by the interaction between meteorology and urban topography, which remains challenging to represent spatially accurately and computationally efficiently in urban dispersion models. Natural topography can additionally exert a considerable amplifying effect on urban background pollution, depending on atmospheric stability. This requires an equally important representation in models, as even subtle terrain-height variations can enforce characteristic local flow regimes. In this model study, the effects of urban and natural topography on the local winds and air pollution dispersion in the Dresden Basin in the Eastern German Elbe valley are investigated. A new, efficient urban microscale model is used within a multiscale air quality modeling framework. The simulations that consider real meteorological and emission conditions focus on two periods in late winter and early summer, respectively, as well as on black carbon (BC), a key air pollutant mainly emitted from motorized traffic. As a complement to the commonly used mass concentrations, the particle age content (age concentration) is simulated. This concept, which was originally developed to study hydrological reservoir flows in a Eulerian framework, is adapted here for the first time for atmospheric boundary-layer modeling. The approach is used to identify stagnant or recirculating orographic air flows and resulting air pollution trapping. An empirical orthogonal function (EOF) analysis is applied to the simulation results to attribute the air pollution modes to specific weather patterns and quantify their significance. Air quality monitoring data for the region are used for model evaluation. The model results show a strong sensitivity to atmospheric conditions, but generally confirm increased BC levels in Dresden due to the valley location. The horizontal variability of mass concentrations is dominated by the patterns of traffic emissions, which overlay potential orography-driven pollutant accumulations. Therefore, an assessment of the orographic impact on air pollution is usually inconclusive. However, using the age-concentration metric, which filters out direct emission effects, previously undetected spatial patterns are discovered that are largely modulated by the surface orography. The comparison with a dispersion simulation assuming spatially homogeneous emissions also proves the robustness of the orographic flow information contained in the age-concentration distribution and shows it to be a suitable metric for assessing orographic air pollution trapping. The simulation analysis indicates several air quality hotspots on the southwestern slopes of the Dresden Basin and in the southern side valley, the Döhlen Basin, depending on the prevailing wind direction.

Development And Application of WRF(v4.1.2)-uEMEP(v5) Model at the City with the Highest Industrial Density: A Case Study of Foshan

“…HYCAMR combines the community model CAMx and the block-scale diffusion model R-LINE to estimate pollutant concentrations in the near-road environment, but does not take into account the emission factors of different roads (Parvez and Wagstrom, 2019). The CAIRDIO-Les large vortex model simulates micrometeorology and air pollution in the Dresden Basin, Germany (Weger and Heinold, 2023). The VEIN-MUNICH model was developed and applied to the road-dense city of Sã o Paulo, Brazil, to predict NOx emissions from road vehicles (Gavidia-Calderón et al, 2021).…”

Aerosol composition, air quality, and boundary layer dynamics in the urban background of Stuttgart in winter

“…Kurppa et al (2019) firstly evaluated the vertical variation of aerosol number concentration and size distribution in a simple street canyon without vegetation in Cambridge by embedding the sectional aerosol module SALSA2.0 (Kokkola et al, 2008(Kokkola et al, , 2018 into the large-eddy simulation model PALM (Maronga et al, 2020). Weger and Heinold (2023) assessed the impact of meteorology and urban topography on the microscale variability of urban air pollution by using LES and empirical orthogonal function (EOF) analysis for the Dresden basin. Their results showed that the model results are strong sensitive to atmospheric conditions, but generally confirm increased eBC levels in Dresden due to the topography.…”