Ozone loss and chlorine activation in the Arctic winters 1991-2003 derived with the tracer-tracer correlations

摘要

Chemical ozone loss in the Arctic stratospherewas investigated for the twelve years between 1991 and 2003 employingthe ozone-tracer correlation method. For this method,the change in the relation between ozone and along-lived tracer is considered for all twelve years over the lifetime of the polarvortexto calculate chemical ozone loss. Both the accumulated local ozone loss in the lowerstratosphere and the column ozone loss werederived consistently, mainly on the basis of HALOE satellite observations.HALOE measurements do not cover the polar region homogeneously over the courseof the winter. Thus, to derive an early winter reference function for eachof the twelve years, all available measurements were additionally used;for two winters climatological considerationswere necessary. Moreover, a detailed quantification of uncertainties was performed.This study further demonstrates the interaction between meteorology andozone loss. The connection between temperature conditions and chlorineactivation, and in turn,the connection between chlorine activation and ozone loss,becomes obvious in the HALOE HCl measurements.Additionally, the degree of homogeneity ofozone loss within the vortex was shown to depend on the meteorological conditions.

Results derived here are in general agreement with the results obtained byother methods for deducing polar ozone loss. Differences occur mainly owing todifferent time periods consideredin deriving accumulated ozone loss. However, very strong ozone losses as deducedfrom SAOZ for January in winters 1993-1994 and 1995-1996 cannot be identified usingavailable HALOE observations in the early winter.In general, strong accumulated ozone loss was found to occur inconjunction with a strong cold vortex containing a large volume ofpossible PSC existence (V_PSC),whereas moderate ozone loss was found if the vortex was less strong andmoderately warm. Hardly any ozone loss was calculated for very warm winters withsmall amounts of V_PSC during the entire winter.This study supports the linear relationship between V_PSCand the accumulatedozone loss reported by Rex et al. (2004) if V_PSC was averagedover the entire winter period. Here, further meteorological factors controllingozone loss were additionally identifiedif V_PSC was averaged over the same time interval as that for whichthe accumulated ozone loss was deduced.A significant difference in ozone loss (of ≈36DU) was found due to thedifferent duration of solar illumination of the polar vortex of at maximum 4 hoursper day in the observed years. Further, the increased burden of aerosols in theatmosphere afterthe Pinatubo volcanic eruption in 1991 significantly increased the extent ofchemical ozone loss.