Total ozone loss during the 2018/19 Arctic winter and comparison toprevious years

International audienceThe amplitude of ozone depletion in the Arctic is monitored every year since 1994 by comparison between totalozone measurements of SAOZ / NDACC UV-Vis spectrometers deployed in the Arctic and 3-D chemical transportmodel simulations in which ozone is considered as a passive tracer.When SAOZ measurements are missing for various reasons, lack of sunlight, station closed or instrumentfailure, they are replaced by IASI Metop-A or IASI Metop-B overpasses above the station. These measurements inthe thermal Infrared are available all year around, at all latitudes even in the polar night. IASI data have been com-pared to SAOZ and to 3-D CTM REPROBUS and the agreement is better than 3% at the latitude of the polar circle.The method allows determining the evolution of the daily rate of the ozone destruction and the amplitudeof the cumulative loss at the end of the winter. The amplitude of the destruction varies between 0-10% in relativelywarm and short vortex duration years to 25-39% in colder and longer ones.However, as shown by the unprecedented depletion of 39% in 2010/11, the loss is not only dependent onthe extension of the vortex in spring, but also on its strength limiting its re-noxification by import of nitrogenoxide species from the outside, as reported by the rapid increase of total NO2columns measured by the SAOZinstruments.Shown in this presentation will be the evolution of ozone loss and re-noxification in the Arctic during thewinter 2018/19 compared to that of previous winters.Compared to observed SAOZ/IASI O3loss, REPROBUS and SLIMCAT CTM simulations are showingsimilar losses, however the agreement may vary from one year to the other, depending on the assumptions ofvortex strength and isolation. The comparison between ozone loss amplitudes and ozone loss rates, seen each yearsince 1994 by SAOZ and the two CTM simulations will be followed by a discussion of possible causes in theirvariable amplitud