Modeling Urban Air Quality in the Berlin-Brandenburg Region: Evaluation of a WRF-Chem Setup

Abstract:

Air pollution is the number one environmental cause of premature deaths in Europe. Despite extensive regulations, air pollution remains a challenging issue, especially in urban areas. For studying 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 (incl. black carbon, VOCs as well as mobile measurements of particle size distribution and particle mass). The model setup includes 3 nested domains with horizontal resolutions of 15km, 3km, and 1km, online biogenic emissions using MEGAN 2.0, and anthropogenic emissions from the TNO-MACC-II inventory.

This work serves as a basis for future studies on different aspects of air pollution in the Berlin-Brandenburg region, including how heat waves affect emissions of biogenic volatile organic compounds (BVOC) from urban vegetation (summer 2006) and the impact of selected traffic measures on air quality in the Berlin-Brandenburg area (summer 2014).

The model represents the meteorology as observed in the region well for both periods. An exception is the heat wave period in 2006, where the temperature simulated with 3km and 1km resolutions is biased low by around 2°C for urban built-up stations.

First results of simulations with chemistry show that, on average, WRF-Chem simulates concentrations of O₃ well. However, the 8 hr maxima are underestimated, and the minima are overestimated. While NO_x daily means are modeled reasonably well for urban stations, they are overestimated for suburban stations. PM₁₀ concentrations are underestimated by the model. The biases and correlation coefficients of simulated O₃, NO_x, and PM₁₀ in comparison to surface observations do not show improvements for the 1km domain in comparison to the 3km domain.

To improve the model performance of the 1km domain we will include an updated emission inventory (TNO-MACC-III) as well as the interpolation of the emission data from 7km to a 1km resolution.