Descent and Mixing in the 1999-2000 Arctic vortex : simulations with the 3-dimensional chemical Lagrangian model of the stratosphere (CLaMS) - Steinhorst, H.; Konopka, Paul; Müller, R.; Grooß, J.-U.; McKenna, D. S.; Elkins, J.; Schmid, F. J.; Toon, G. (2002)