Anthropological Perspectives

Abstract

The Match method quantifies chemical ozone loss in the polar stratosphere. The basic idea consists in calcu-lating the forward trajectory of an air parcel that has been probed by an ozone measurement (e.g., by an ozonesonde or satellite instrument) and finding a second ozone mea-surement close to this trajectory. Such an event is called a " match " . A rate of chemical ozone destruction can be ob-tained by a statistical analysis of several tens of such match events. Information on the uncertainty of the calculated rate can be inferred from the scatter of the ozone mixing ratio dif-ference (second measurement minus first measurement) as-sociated with individual matches. A standard analysis would assume that the errors of these differences are statistically independent. However, this assumption may be violated be-cause different matches can share a common ozone measure-ment, so that the errors associated with these match events become statistically dependent. Taking this effect into ac-count, we present an analysis of the uncertainty of the fi-nal Match result. It has been applied to Match data from the Arctic winters 1995, 1996, 2000, and 2003. For these ozonesonde Match studies the effect of the error correlation on the uncertainty estimates is rather small: compared to a standard error analysis, the uncertainty estimates increase by 15% on average. However, the effect may be more pro-nounced for typical satellite Match analyses: for an Antarc-tic satellite Match study (2003), the uncertainty estimates in-crease by 60% on average. The analysis showed that the random errors of the ozone measurements and the " net match errors " , which result from a displacement of the second ozone measurement of a match from the required position, are of similar magnitude. This demonstrates that the criteria for accepting a match (max-imum trajectory duration, match radius, spread of trajec-tory clusters etc.) ensure that, given the unavoidable ozone-Correspondence to: R. Lehmann (rlehmann@awi-potsdam.de) measurement errors, the magnitude of the net match er-rors is adequate. The estimate of the random errors of the ozonesonde measurements agrees well with laboratory re-sults.