Lagrangian Simulations of polar ozone loss: from box model to 3-d CTM CLaMS

Since the discovery of the ozone hole in 1985, simulations of polar ozone loss improved persistently over the years. Especially using the Lagrangian view in which chemical processes are simulated for air parcels that move in location has been demonstrated to be a successful method. We describe the development of Lagrangian simulations of polar ozone loss starting with chemical box model simulations along particular trajectories up to the 3-dimensional version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). Besides chemistry and Lagrangian advection CLaMS contains sophisticated modules for mixing and denitrification. We show CLaMS simulations for the Arctic winters 2002/03, 2004/05 and for the Antarctic winter 2003. The focus will be on chemical ozone loss and denitrification. The processes involved in denitrification, especially the nucleation of NAT particles are not fully understood. From comparisons of the simulated denitrification with observations we conclude that the sensitivity of denitrification on key assumptions is largest at the time of onset of the denitrification. Further we show that besides possible inconsistencies in the ozone loss rates in early winter the ozone depletion over the winter is simulated in agreement with the observations. Overall, CLaMS simulations reproduce the inhomogeneity of chemical ozone loss within the polar vortex well.