A three-dimensional modeling study of trace species in the Arctic lower stratosphere during winter 1989-1990

Abstract

Model simulations in late December show that inside the polar vortex air is rapidly processed by polar stratospheric clouds converting HCl and ClONO2 to active chlorine. In early February an average ozone loss of 15 ppbv (parts per billion by volume)/day is predicted in PSC-processed air at 50 hPa, giving a column loss of just under 1 DU/day. This loss increases to 25 ppbv/day if PSCs persist until March with a column loss of around 1.5 DU/day. The relatively small magnitude of the ozone loss predicted in the model, compared to the variability of ozone induced by dynamics, highlights the problems in identifying the signature of chemical ozone loss in the Arctic. In future years significant ozone depletion could occur if PSCs persist until late March. In general, the cycle involving ClO + ClO is the dominant loss mechanism in the polar lower stratosphere. Cycles involving BrO can make a relatively large contribution early in the season and when the levels of ClO are low. The cycle initiated by ClO + O destroys ozone at altitudes above 30 hPa but the loss is compensated, to some extent, by in situ ozone production. -from Authors