On the distribution of ozone in stratospheric anticyclones

Twelve years (1991-2003) of satellite occultation ozone data are combined with a climatology of stratospheric anticyclones and polar vortices to quantify the climatological ozone differences between air mass types. Ozone data from the Stratospheric Aerosol and Gas Experiment (SAGE) II, the Halogen Occultation Experiment (HALOE), the Polar Ozone and Aerosol Measurement (POAM) II and III missions, and the Improved Limb Atmospheric Spectrometer (ILAS) sensor are used in this study. Daily ozone measurements in the 400-1600 K altitude range are categorized as being either ( 1) in an anticyclone, ( 2) in a polar vortex, or (3) in neither (hereinafter referred to as "ambient''). Monthly mean ozone is then calculated in each air mass category from data combined over all years. This study focuses on ozone differences between anticyclones and the ambient environment. A composite annual cycle of ozone in ambient regions is compared to ozone in anticyclones as a function of altitude and latitude. Ozone differences result from both anomalous transport and photochemistry in the vicinity of stratospheric anticyclones. The relative importance of transport versus chemistry is inferred from the long-term ozone anomalies observed here. In summer, ozone gradients between different air mass types are small. In other seasons, results indicate three distinct vertical regimes at high latitudes. Below approximate to600 K, anticyclones coincide with regions where ozone is reduced by 10-50% during the winter. Between 600 and 900 K from fall to midwinter, anticyclones are associated with approximate to10% more ozone than ambient air masses. Positive ozone anomalies are also observed in low-latitude anticyclones within this vertical layer; however, they are half the size of their high-latitude counterparts and peak several months later. Above 900 K the abundance of ozone in anticyclones is approximate to10% less than in the surrounding air. This upper stratospheric regime results from the formation of "low-ozone pockets'' (LOPs) in stratospheric anticyclones. All LOPs that formed between November 1991 and November 2003 and were observed by a satellite used in this study ( 108 pockets) are documented here in the most comprehensive catalog of LOPs to date.