Model calculations of ozone depletion in the Arctic Polar Vortex for 1991/92 to 1994/95

We have used a 3D chemical transport model to investigate the potential for chemical ozone depletion in the Arctic polar vortex for the past 4 winters. By using the same chemical initial conditions for each winter we have isolated the effects of meteorological variability on polar ozone loss. These calculations show that during 1994/95 conditions in the Arctic polar vortex were the most conducive to ozone depletion in recent years. Our numerical experiments show that at 475 K (around 18 km) in the lower stratosphere the chemical ozone destruction between late December and mid March was greater than 30% over a large area of the polar vortex. Larger percentage losses, reaching 50%, occur at slightly lower altitudes. The average model depletion in the entire region poleward of 60°N over the same period was around 22% at 475 K. Similar calculations for the preceding three Arctic winters show less depletion. The large depletion for 1994/95 is a consequence of the extreme meteorological conditions during this winter.