One of the largest ozone holes in years
EOC assessments show that this year’s ozone hole is one of the largest since measurements began. The record size can probably be attributed to the 2022 eruption of Hunga Tonga volcano.
One of the largest ozone holes in years
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The ozone destruction is primarily caused by the decades-long industrial use of chlorofluorocarbons (CFC) that accumulated in the atmosphere. The ozone hole season usually begins in mid August, early springtime in the Antarctic. That is the season when ideal conditions rule there for ozone destruction: especially low temperatures combined with enough solar illumination.
One speaks of an ozone hole as soon as satellite measurements of the amount of ozone fall below a certain concentration (220 Dobson units). Measurements made by Europe’s Sentinel-5P (S5p) satellite sporadically showed values under this limit already in August. The thinning out ultimately extended over an area of 26 million km² on September 16th, making it one of the largest ozone holes ever observed.
The Sentinel-5P data are processed in near real-time at EOC and the resulting ozone level observations are distributed to users such as the Copernicus Atmosphere Monitoring Service (CAMS) within just a few hours. CAMS senior scientist Antje Inness attributes this year’s record size to a volcanic eruption:
"The eruption of the Hunga Tonga volcano in January 2022 injected a lot of water vapour into the stratosphere which only reached the south polar regions after the end of the 2022 ozone hole.
The water vapour could have led to the heightened formation of polar stratospheric clouds, where chlorofluorocarbons (CFCs) can react and accelerate ozone depletion. The presence of water vapour may also contribute to the cooling of the Antarctic stratosphere, further enhancing the formation of these polar stratospheric clouds and resulting in a more robust polar vortex.”
The size of the ozone hole varies from year to year since ozone breakdown and concentration are influenced by the temperature and by dynamic airstreams in the upper atmosphere. The good news is that the concentration of CFCs has gradually decreased over the past twenty years and the ozone layer is recovering. The use of CFCs has been prohibited in many countries since the Montreal Protocol of 1986. However, since CFCs are very long-lasting the effect of their prohibition can be noted only after a delay, so complete recovery of the ozone layer could require up to 50 years. The bad news is that climate change makes the troposphere (which extends up to an altitude of ca.10-18 km) warmer and the stratosphere (up to 60 km altitude) colder, which slows down the recovery.
Monitoring
Only with the help of satellites is it possible to continuously and comprehensively monitor the ozone layer globally. Measurements from the TROPOMI instrument on Sentinel-5 Precursor (S5p), a Copernicus programme satellite, are extending the lengthy time series of European measurements that began already in 1995 with GOME (Global Ozone Monitoring Experiment) on ERS-2. The measurement series was then expanded first with SCIAMACHY on Envisat, and afterwards with OMI on AURA and the GOME-2 instrument on the METOP satellites.
At DLR data from the TROPOMI instrument are being assessed as part of the ESA/EU S5p project, and data from the GOME-2 instruments are analysed for the EUMETSAT project ACSAF (Atmospheric Composition Satellite Application Facility). In addition, all these measurements are used by DLR to draw up a consistent time series for the EU project C3S (Copernicus Climate Change Service) of the ECMWF (European Centre for Medium-Range Weather Forecasts). With this tool the long-term evolution of the ozone layer can be more effectively monitored.
As part of the DLR project INPULS (Innovative Product Development for Analyzing the Atmosphere Composition), the S5P measurements are being processed and visualized and animations of the ozone hole generated.