Impact of stratospheric dynamics and chemistry on northern hemisphere mid-latitude ozone loss

摘要

The importance of stratospheric dynamics for the stratospheric ozone distribution in the Northern Hemisphere is investigated using multi-annual simulations of the coupled dynamic-chemical general circulation model ECHAM3/CHEM. This model includes a parameterization for heterogeneous reactions on polar stratospheric clouds (PSC) and on sulphate aerosols. A warm and a cold stratospheric winter are examined to estimate the range of chemical ozone loss due to heterogeneous reactions on PSCs. Ozone depletion in the model mainly occurs inside the polar vortex. An additional ozone reduction due to heterogeneous reactions on PSCs is found as well outside the polar vortex. Secondary vortex formation and vortex contraction after an elongation lead to a transport of airmasses with chemically reduced ozone values out of the vortex. Except for such events, the edge of the modeled polar vortex acts as a barrier to transport. During the formation of secondary vortices, no additional heterogeneous reactions occur therein. Other dynamic events like the elongation of the polar vortex and its displacement to lower latitudes lead to an intense ozone depletion. A modeled minor stratospheric warming causes a total deactivation of chlorine components and prevents further ozone depletion. In mid-latitudes, the amplitude of short-term variations of total ozone is amplified by PSC heterogeneous chemical ozone reduction. (orig.) 27 refs.