More than 60% ozone loss at 18 km

Between early January and late March more than 60% of the ozone at 475 K (or approx.18 km) was destroyed due to man-made ozone depleting substances (mainly CFCs and halons).

Figure 1 shows the temporal development of the vortex average ozone concentration profile. See figure caption for a more detailed explanation.

Figure 2 shows the temporal development of the ozone mixing ratio at the level of 475 K (approx. 18 km) during the winter. See figure caption for a more detailed explanation.

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Figure 1. Evolution of the vortex averaged ozone profile from January to March 2000. The blue profiles reflect the inner vortex ozone profile we would expect in late March without any chemical loss. Diabatic subsidence is taken into account by advecting the vortex averaged mixing ratio profiles passively until late March, using estimated diabatic cooling rates. After the advection, the ozone concentrations were calculated from the mixing ratios, using the vortex averaged pressure and temperature profiles from late March. The first and the last profiles are emphasised with thicker lines. Possible mixing across the vortex edge is not taken into account. However, the large losses illustrated here are consistent with preliminary analyses from the more comprehensive Match study.

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More information about these results can be obtained from Markus Rex, Alfred Wegener Institute, Potsdam. E-mail: mrex@awi-potsdam.de
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Figure 2. Evolution of the ozone mixing ratio inside the polar vortex from December 1999 through March 2000. The red dots represent individual ozone soundings made from more than 10 stations inside the polar vortex. The blue curve is an 11 day running average. The ozone loss from early January until late March is approx. 2.3 ppm. If one takes into consideration the fact that air masses subside during the winter (diabatic cooling) the ozone loss is approx. 2.5 ppm. The diabatic cooling rates have been provided by Björn-Martin Sinnhuber and Martyn Chipperfiled, Univ. of Leeds.

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More information on this analysis can be obtained from Geir Braathen at the Norwegian Institute for Air Research. E-mail: geir@nilu.no
Last updated 5 April 2000 by Geir Braathen, NILU.