Trajectory photochemical model for the lower stratosphere

A model is presented to study the dynamical and chemical processes responsi ble for ozone loss in the lower stratosphere. The continuity equation for a chemical species is integrated along the trajectory of air particle motion ; i.e., a Lagrangian approach is employed to describe the motion of a conti nuous medium. The trajectories are estimated using the European Center for Medium-range Weather Forecast (ECMWF) data. The trajectory photochemical mo del can be widely used to interpret experimental data and to trace the evol ution of air masses arriving at the measurement site. The method described in this work permits the calculation of thousands of back trajectories for various initial coordinates by using the chemical. model for each trajector y. This approach (a multitrajectory model) is actually a three-dimensional Lagrangian chemical transport model.