Satellite observations of relevant trace gases, together with meteorological
data from ERA5, were used to describe the dynamics and chemistry of the spectacular Arctic
2019/20 winter/spring season. Exceptionally low total ozone values of slightly less
than 220 DU were observed in mid March within an unusually large stratospheric polar
vortex.
This was associated with very low temperatures and extensive polar stratospheric cloud
formation, a prerequisite for substantial springtime ozone depletion. Very high OClO
and very low NO2 column amounts observed by GOME-2A are indicative of unusually
large active chlorine levels and significant denitrification, which likely contributed to
large chemical ozone loss. Using results from the TOMCAT chemical transport
model (CTM) and ozone observations from S5P/TROPOMI, GOME-2 (total column), SCIAMACHY and OMPS-LP
(vertical profiles) chemical ozone loss was evaluated and compared with the previous
record Arctic winter 2010/11. The polar-vortex-averaged total column ozone loss in
2019/20 reached 88 DU (23%) and 106~DU (28%) based upon observations and model,
respectively, by the end of March, which was similar to that derived for 2010/11. The
total column ozone loss is in agreement with OMPS-LP-derived partial column loss
between 350 K and
550 K to within the uncertainty. The maximum ozone loss (~80%)
observed by OMPS-LP was near the 450 K potential
temperature level (~18 km altitude). Because of the larger polar vortex area in
March 2020
compared to March 2011 (about 25% at 450 K), ozone mass loss was larger in Arctic winter 2019/20.