资源环境科技发展态势分析平台

Newsflash Reading 07/04/2020.

Total column ozone field (in Dobson Units) from CAMS in its largest extent on 29 March 2020 (left) and 06 April 2020 (right) showing values below 250 DU over large parts of the Arctic. Credit: Copernicus Atmosphere Monitoring Service/ECMWF.

The Copernicus Atmosphere Monitoring Service (CAMS), implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Commission, reports that ozone columns over large parts of the Arctic have reached record low values this year, causing an ozone hole to form. While the Antarctic ozone hole forms every year during Austral spring, the last time similarly strong chemical ozone depletion was observed over the Arctic was during Boreal spring 2011, and CAMS scientists expect Arctic ozone depletion in 2020 to be even stronger.

Timeseries of Northern Hemisphere ozone column minimum (in Dobson Units) from CAMS (2003–2020) and C3S (1980–2002) data (shown is the range of minimum values per decade) illustrating how exceptionally low the ozone column minimum values have been so far in 2020 (black line). Credit: Copernicus Atmosphere Monitoring Service/ECMWF.

CAMS is contributing to the international efforts of preserving the ozone layer by continually monitoring and delivering high quality data about its current state, like reporting the smallest Antarctic ozone hole in 35 years last November. Measurements from satellites are combined with computer models of the atmosphere in a similar way to weather forecasts. Monitoring the ozone hole is important as the stratospheric ozone layer acts as a shield, protecting all life on Earth from potentially harmful ultraviolet radiation.

CAMS has been closely following the unusual activity in the ozone layer happening over large parts of the Arctic this spring and its findings show that most of the ozone in the layer between 80 and 50 hPa, at around 18 kilometres altitude, has been depleted.

Left panel: Comparison of ozone profiles (in mPa) from CAMS (red) and independent ozonesonde instruments (black) at the Arctic station of Ny-Ålesund on 26 March 2020. Right panel: Mean ozone profiles at Ny-Ålesund from CAMS (yellow) and ozonesondes (black) averaged over the years 2003–2019. The shaded area denotes +/- 1 standard deviation. Credit: Copernicus Atmosphere Monitoring Service/ECMWF.

While every year an ozone hole develops over the Antarctic during the Austral spring, ozone holes in the Arctic are rare, since the conditions needed for such strong ozone depletion are not normally found in the Northern Hemisphere. The Arctic stratosphere is usually less isolated than its Antarctic counterpart, because the presence of land masses and mountain ranges at high latitudes in the Northern Hemisphere disturbs the weather patterns, making the polar vortex weaker and more perturbed.

“Our forecasts suggest that temperatures have now started to increase in the polar vortex”, comments Vincent-Henri Peuch, Director of the Copernicus Atmosphere Monitoring Service. “This means that ozone depletion will slow down and eventually stop, as polar air will mix with ozone-rich air from lower latitudes. CAMS will continue to monitor the evolution of the Arctic ozone hole over the coming weeks. It is very important to maintain international efforts for monitoring the annual ozone hole events and the ozone layer over time.”

Timeseries of minimum temperature (north of 60⁰N) in the stratosphere at an altitude where the pressure measures 50 hPa from CAMS (2003 onwards) and C3S (1980–2002) data illustrating that minimum stratospheric temperatures at 50 hPa during winter and spring 2020 (black line) were below the temperature threshold for PSC formation (-78 degrees Celsius) for several months. Credit: Copernicus Atmosphere Monitoring Service/ECMWF.

How the ozone hole is formed

Chlorine and bromine-containing substances accumulate within the polar vortex where they stay chemically inactive in the darkness. Temperatures in the vortex can fall to below -78 degrees Celsius and ice crystals in Polar stratospheric clouds can form, which play an important part in the chemical reactions. As the sun rises over the pole, the sun’s energy releases chemically-active chlorine and bromine atoms in the vortex which rapidly destroy ozone molecules, causing the hole to form.

More information about the ozone hole, you can find in our web article.