Impact of heterogeneous reactions on stratospheric chemistry of the Arctic

The possible depletion of ozone due to heterogeneous reactions occuring in Arctic polar stratospheric clouds (PSC's) is fundamentally different from the Antarctic situation. PSC's in the Arctic are relatively short‐lived and occur over limited regions of the Arctic stratosphere. We have examined the Arctic situation using a model which calculates photochemical processes as a function of longitude in air circulating with fixed velocity around the pole at fixed pressure level and latitude. The model allows sunlight to vary diurnally and PSC's to occur in specified subregions of the domain. Measurements of chemical species including HCl, ClO, NO 2 and HNO 3 downwind from a PSC should show obvious changes compared to measurements in air unaffected by clouds. These species concentrations are found to be sensitive to sticking coefficients, cloud characteristics including particle number density and surface area, and to the PSC exposure time.