The global mass of ozone: 1978-1998

Global measurements of total column ozone from five inter-compared satellit e-based instruments were used to calculate the daily global mass of ozone f rom November 1978 to December 1998. Missing data in polar darkness were est imated by interpolation across thc polar caps. Global ozone mass and ozone mass totalled over 30 degrees latitude zones were examined for the mean ann ual cycle, its evolution over the 20 year period, the impacts of volcanic e ruptions and hemispheric differences in these impacts. Ozone mass for the g lobe or within a latitude zone is more suitable than mean column amount (e. g. in Dobson Units) because it is invariant under transport within zones an d is a direct measure of exchange between zones. Furthermore, the relative contribution of impacts at different latitudes to global changes in ozone c an be more easily quantified. While global ozone mass is significantly pert urbed by high latitude wintertime ozone depletion, the impact of the Mt. Pi natubo eruption on northern midlatitude ozone mass was larger than any sing le Antarctic ozone hole event.