The transport and further chemical processes of pollutants in the atmosphere can be simulated with chemistry transport models. The Helmholtz-Zentrum Geesthacht (HZG) uses the Community Multiscale Air Quality (CMAQ) model system in their investigations for Europe. Meteorological fields calculated with the regional atmospheric model COSMO-CLM were used as input data. For our purpose, COSMO-CLM was driven with NCEP re-analysis data using spectral nudging. The anthropogenic emissions used were derived with the SMOKE for Europe emission model (Bieser et al., 2011).
In this project, there is a special focus on the dispersion of emissions from ships in the North and Baltic Sea region. The ship emissions used in the model are based on individual ship movements and their individual characteristics, like ship engines and types of fuel used. The gas-to-particle conversion in the atmosphere plays an important role for the atmospheric concentrations of pollutants and for their dispersion. Gaseous sulphur dioxide (SO2) and nitrogen oxides (NOx) from ships are converted into sulphate (SO4) and nitrate (NO3) aerosols (particulate matter, PM), particularly in summer. They may then be transported hundreds of kilometres inland.
The simulation above shows such an episode in the late summer of 2008. Ship emissions west of France and in the English Channel lead to aerosol formation. Interaction with ammonia emissions (NH3) from land favors the formation of particles. The aerosol particles are then transported westwards to Central Europe. Particularly in coastal regions, aerosols from ship emissions may contribute significantly to the total anthropogenic aerosol load (Matthias et al., 2010).
The color shading in the animation below also shows the development of the near surface aerosol concentrations. Additionally, semi transparent isosurfaces were used to show the 3D structure of the aerosol clouds.
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