Air quality modelling in the Berlin–Brandenburg region using WRF-Chem v3.7.1: sensitivity to resolution of model grid and input data

• Published in: Geoscientific Model Development 2016-12, Vol.9 (12), p.4339-4363
• Main Authors: Kuik, Friderike, Lauer, Axel, Churkina, Galina, Denier van der Gon, Hugo A. C, Fenner, Daniel, Mar, Kathleen A, Butler, Tim M
• Format: Article
• Language: English
• Subjects: Aerosols; Air monitoring; Air pollution; Air pollution control; Air quality; Air quality models; Analysis; Anthropogenic factors; Atmospheric chemistry; Canopies; Canopy; Chemistry; Computer simulation; Data; Daytime; Emissions; Environmental monitoring; Height; Land use; Mathematical models; Meteorological research; Meteorology; Mixed layer; Mixed layer height; Modelling; Monitoring systems; Night; Night-time; Nighttime; Nitrogen compounds; Nitrogen dioxide; Numerical weather prediction; Outdoor air quality; Oxides; Ozone; Parameter sensitivity; Parameters; Particulate emissions; Particulate matter; Pollutants; Population density; Resolution; Secondary aerosols; Sensitivity; Simulation; Spatial discrimination; Spatial distribution; Spatial resolution; Studies; Suspended particulate matter; Traffic volume; Trans-Neptunian objects; Urban areas; Urban land use; Urban meteorology; Weather forecasting; Wind speed
• ISSN: 1991-9603; 1991-959X; 1991-962X; 1991-9603; 1991-962X
• DOI: 10.5194/gmd-9-4339-2016

Air pollution is the number one environmental cause of premature deaths in Europe. Despite extensive regulations, air pollution remains a challenge, especially in urban areas. For studying summertime air quality in the Berlin–Brandenburg region of Germany, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) is set up and evaluated against meteorological and air quality observations from monitoring stations as well as from a field campaign conducted in 2014. The objective is to assess which resolution and level of detail in the input data is needed for simulating urban background air pollutant concentrations and their spatial distribution in the Berlin–Brandenburg area. The model setup includes three nested domains with horizontal resolutions of 15, 3 and 1 km and anthropogenic emissions from the TNO-MACC III inventory. We use RADM2 chemistry and the MADE/SORGAM aerosol scheme. Three sensitivity simulations are conducted updating input parameters to the single-layer urban canopy model based on structural data for Berlin, specifying land use classes on a sub-grid scale (mosaic option) and downscaling the original emissions to a resolution of ca. 1 km × 1 km for Berlin based on proxy data including traffic density and population density. The results show that the model simulates meteorology well, though urban 2 m temperature and urban wind speeds are biased high and nighttime mixing layer height is biased low in the base run with the settings described above. We show that the simulation of urban meteorology can be improved when specifying the input parameters to the urban model, and to a lesser extent when using the mosaic option. On average, ozone is simulated reasonably well, but maximum daily 8 h mean concentrations are underestimated, which is consistent with the results from previous modelling studies using the RADM2 chemical mechanism. Particulate matter is underestimated, which is partly due to an underestimation of secondary organic aerosols. NOx (NO + NO2) concentrations are simulated reasonably well on average, but nighttime concentrations are overestimated due to the model's underestimation of the mixing layer height, and urban daytime concentrations are underestimated. The daytime underestimation is improved when using downscaled, and thus locally higher emissions, suggesting that part of this bias is due to deficiencies in the emission input data and their resolution. The results further demonstrate that a horizontal resolution o