the Lagrangian air parcels. Their trajectories are determined using the horizontal winds and their vertical settling velocity that depends on the size of the individual particles. NAT particles are nucleated assuming a constant nucleation rate and they evaporate where temperatures grow too high. With this, a vertical redistribution of HNO3 (denitrification and renitrification) is determined. CLaMS data sets A chemical transport model does not simulate the dynamics of the atmosphere. For CLaMS, the following meteorological data sets have been used European Centre for Medium-Range Weather Forecasts (ECMWF), Predictions, Analyses, ERA-15, ERA-40 United Kingdom Met Office (UKMO) European Centre Hamburg Atmospheric Model (ECHAM4), in the DLR version To initialize the chemical fields in CLaMS, data from a large variety of instruments have provided data. on satellite (CRISTA, MIPAS, MLS, HALOE, ILAS, ...), on aircraft and balloons (HALOX, FISH, Mark IV, BONBON...) If no observations are present, the chemical fields can be initialised from two-dimensional chemical models, chemistry-climate models, climatologies, or from correlations between chemical species or chemical species and dynamical variables. See also Forschungszentrum Jülich Ozone depletion Meteorology External links CLaMS at Forschungszentrum Jülich Current field campaign SCOUT-O3 References The details of the model CLaMS are well documented and published in the scientific literature. Formulation of advection and mixing by McKenna et al., 2002a Formulation of chemistry-scheme and initialisation by McKenna et al., 2002b Comparison of the chemistry module with other stratospheric models by Krämer et al., 2003 Calculation of photolysis rates by Becker et al., 2000 Extension to 3-dimension model version by Konopka et al., 2004 Lagrangian sedimentation by Grooß et al., 2005 Numerical climate and weather models Ozone depletion