Chemical ozone losses in Arctic and Antarctic polar winter/spring season derived from SCIAMACHY limb measurements 2002–2009

Abstract. Stratospheric ozone profiles are retrieved for the period 2002–2009 from SCIAMACHY measurements of limb-scattered solar radiation in the Hartley and Chappuis absorption bands of ozone. This data set is used to determine the chemical ozone losses in both the Arctic and Antarctic polar vortices by averaging the ozone in the vortex at a given potential temperature. The chemical ozone losses at isentropic levels between 450 K and 600 K are derived from the difference between observed ozone abundances and the ozone modelled taking diabatic cooling into account, but no chemical ozone loss. Chemical ozone losses of up to 30–40% between mid-January and the end of March inside the Arctic polar vortex are reported. Strong inter-annual variability of the Arctic ozone loss is observed, with the cold winters 2004/2005 and 2006/2007 showing chemical ozone losses inside the polar vortex at 475 K, where 1.7 ppmv and 1.4 ppmv of ozone were removed, respectively, over the period from 22 January to beginning of April and 0.9 ppmv and 1.2 ppmv, respectively, during February. For the winters of 2007/2008 and 2002/2003, ozone losses of about 0.8 ppmv and 0.4 ppmv, respectively are estimated at the 475 K isentropic level for the period from 22 January to beginning of April. Essentially no ozone losses were diagnosed for the relatively warm winters of 2003/2004 and 2005/2006. The maximum ozone loss in the SCIAMACHY data set was found in 2007 at the 600 K level and amounted to about 2.1 ppmv for the period between 22 January and the end of April. Enhanced losses close to this altitude were found in all investigated Arctic springs, in contrast to Antarctic spring. The inter-annual variability of ozone losses and PSC occurrence rates observed during Arctic spring is consistent with the known QBO effects on the Arctic polar vortex, with exception of the unusual Arctic winter 2008/2009.

The maximum total ozone mass loss of about 25 million tons was found in the cold Arctic winter of 2004/2005 inside the polar vortex between the 450 K and 600 K isentropic levels from mid-January until the middle of March.

The Antarctic vortex averaged ozone loss as well as the size of the polar vortex do not vary much from year to year. The total ozone mass loss inside the Antarctic polar vortex between the 450 K and 600 K isentropic levels is about 50–60 million tons and the vortex volume for this altitude range varies between about 150 and 300 km³ for the period between mid-August and mid-November of every year studied, except for 2002. In 2002 a mid-winter major stratospheric warming occurred in the second half of September and the ozone mass loss was only about half of the value in the other years. However, inside the polar vortex we find chemical ozone losses at the 475 K isentropic level that are similar to those in all other years studied. At this isentropic level ozone losses of 70–90% between mid-August and mid-November or about 2.5 ppmv are observed every year. At isentropic levels above 500 K the chemical ozone losses were found to be larger in 2002 than in all other years studied.

Comparisons of the vertical variation of ozone losses derived from SCIAMACHY observations with several independent techniques for the Arctic winter 2004/2005 show that the SCIAMACHY results fall in the middle of the range of previously published results for this winter. For other winters in both hemispheres – for which comparisons with other studies were possible – the SCIAMACHY results are consistent with the range of previously published results.