The effect of small-scale inhomogeneities on ozone depletion in the Arctic

THE chemical processes involved in the depletion of polar stratospheric ozone are now fairly well understood. But the effect of small-scale stirring and mixing of the chemical species involved can be misrepresented in three- dimensional chemical-transport models because of their coarse resolution. Because of the nonlinearities in the chemical rate laws, especially those involving chlorine in the main catalytic cycle, these effects can be important-particularly in the Arctic, where the polar vortex is less uniform and less isolated from surrounding air than in the Antarctic. Here we use a very-high-resolution model with simplified ozone-depletion chemistry to show that the depletion is sensitive to small-scale inhomogeneities in the distribution of reactant species. Under the conditions of the winter of 1994- 95 the effect is large enough to account for the observed discrepancies of about 40% between modelled and observed ozone depletion in the Arctic environment.