Chemical ozone loss in a chemistry-climate model from 1960-1999

Abstract

In the recent WMO assessment of ozone depletion, the minimum ozone column is used to assess the evolution of the polar ozone layer simulated in several chemistry-climate models (CCMs). The ozone column may be strongly influenced by changes in transport and is therefore not well-suited to identify changes in chemistry. The quantification of chemical ozone depletion can be achieved with tracer-tracer correlations (TRAC). For forty Antarctic winters (1960–1999), we present the seasonal chemical depletion simulated with the ECHAM4.L39(DLR)/CHEM model. Analyzing methane–ozone correlations, we find a mean chemical ozone loss of 80 ± 10 DU during the 1990s, with a maximum of 94 DU. Compared to ozone loss deduced from HALOE measurements the model underestimates chemical loss by 37%. The average multidecadal trend in loss from 1960 to 1999 is 17 ± 3 DU per decade. The largest contribution to this trend comes from the 62 ± 11 DU ozone loss increase between the 1970s and 1990s.