Source Reconstruction for the ETEX-1 Tracer Release with a Lagrangian Dispersion Model

Preliminary studies (Seibert, 1997; Seibert, 1999) used simple trajectories to provide a first approximation to the SRM. This approach already yields useful results and can be used instead of more conventional trajectory statistics. However, a real dispersion model (Eulerian or Lagrangian) is needed for an accurate description of the source-receptor matrices. Receptor-oriented Lagrangian models are computationally efficient if the number of receptors (measurements) is less than the number of potential source elements. The usual choice in this case was for a long time the Lagrangian box model. It has the advantage that chemistry can be included, but does not describe transport and dispersion very well (problems related, e.g., to wind shear). As our approach for inversion anyway does not allow for non-linear chemical reactions, a Lagrangian particle dispersion model (LPDM) was an attractive choice as it offers high accuracy though no chemistry is included.