Long range transport of air pollutants as estimated by a trajectory model

Back trajectories are computed each 6 hours for a number of stations located within the boundaries of the participating OECD countries. As an air parcel moves along its trajectory sulphur dioxide is absorbed at a rate proportional to the strength of the underlying sources. Chemical transformation of SO2 to SO4, as well as deposition to the ground, are also simulated in a simple way. The computed concentrations are compared with daily measurements in order to demonstrate the efficiency of the model, using various transport winds between the surface and the 850 mb. The transformation rates and the deposition rates are also varied in order to see the influence of these parameters on the model estimates.