Interannual variability of ozone loss in the Arctic and Antarctic polar vortex using 20 years of NDACC ozone measurements
Résumé
Since 1990, stratospheric chemical ozone losses in the Arctic have been reported, but the large activity of planetary waves in the northern hemisphere makes the evaluation of photochemical destruction far more difficult than in the southern hemisphere. To overcome the difficulty, several methods for removing the contribution of transport have been suggested. Among those is the transport model approach. With this method, chemical ozone reduction is derived by comparison between ground based total ozone measurements and 3D model simulations in which ozone is considered as a passive tracer. Using this method, the total ozone reduction in the Arctic vortex was derived each winter since winter 1994 by comparing the SAOZ/NDACC measurements to two 3D CTM, Reprobus and Slimcat. The method allows determining the period of ozone destruction, the daily rate and the amplitude of the cumulative loss. The amplitude of the ozone loss is very sensitive to stratospheric temperature history during the winter and thus highly variable from one winter to another. In general, strongest ozone losses of 25-30 % are occurring during coldest winters while very little 0-10% could be observed during the warmest. There is an exception for the winter 2011 when a record low value of 39% has been measured. This 39% loss is close to the depletion reported in the Antarctic regions using the same method and SAOZ measurements together with other ground-based observations such as Dobson or other UV-visible DOAS/NDACC instruments, where during the last 23 years of available measurements the ozone loss is reaching 50-52%, except in 2002 when it was limited to 40%.