WMO Antarctic Ozone Bulletin #8/2001 Issued on 13 December 2001

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1. The Secretariat of the World Meteorological Organization (WMO) distributes Bulletins providing current Antarctic ozone hole conditions during August-December each year. Bulletins are distributed via the WMO-Global Telecommunication System (GTS) and are also available through the Atmospheric Research and Environment Programme web page at www.wmo.ch/web/arep/ozone.html . In addition to the National Meteorological Services, the information in these Bulletins should be made available to the national bodies representing their countries with UNEP and that support or implement the Vienna Convention for the Protection of the Ozone Layer and its Montreal Protocol.

2. Meteorological conditions: As Austral Summer approaches and solar radiation increases over Antarctica, minimum stratospheric temperatures in the ozone hole have continued to increase, and are well above those necessary for the formation of polar stratospheric clouds (PSCs). This effectively "turns off" those conditions necessary to form the ozone hole each year. The polar vortex has weakened significantly, and has completely disappeared at the upper levels of the ozone hole. Although PSCs and the polar vortex persisted longer than usual during 2001, the meteorological conditions necessary to sustain this years ozone hole have ended.

3. Observed ozone changes: Ground-based and satellite observations report the expected seasonal increase in ozone from the minimum values reported early in October. Ozone measurements during the first 10 days of December were up to 45% below pre-ozone hole norms, but presently they are no more than 30% below norms over the Antarctic continent. The persistent pocket of exceptionally low ozone with more than 50% depletion reported in the 22 November Bulletin, quickly dissipated during late November. Ozone over the populated regions of the southern tip of South America have generally remained near normal, although Ushuaia, Argentina has been 25-30% below pre-ozone hole norms during the last few days, possibly due to the break-up and dispersal of the ozone hole. Ozone measurements made from balloons flown from the Antarctic continent during early December also confirm that the stratospheric ozone layer is recovering. Consistent with the disappearance of the polar vortex at upper levels, ozone has rapidly increased above 19 kilometres (km), but highly depleted ozone levels remain below 16 km at most reporting stations.

4. Ozone hole characteristics: During the past few days, the very low ozone values characteristic of the ozone hole have practically disappeared. This is the result of mixing ozone rich air into the ozone hole region and dispersal of the highly depleted air to the North. In previous Bulletins the "ozone mass deficit" was described as the mass of ozone destroyed in the Antarctic region, expressed in millions of tons (Mt) of ozone and estimated by comparison of the daily ozone data available from satellites and ground stations with the pre-ozone hole norms. The ozone mass deficit, presently about 35 Mt, remains seasonally higher than all previous years, contrasting the large ozone hole of 2000 when the mass deficit had decreased to less than 5 Mt by 10 December. The duration of the very low ozone values over Antarctica has a great influence on UV levels experienced at ground level in and near Antarctica. UV radiation measured at the Antarctic stations of Palmer and South Pole showed significant increases that are attributed to the ozone hole, and McMurdo station has recorded UV levels among the highest ever measured by the NSF spectroradiometer at that site.

5. Comment: This is the last WMO Antarctic Ozone Bulletin to be issued this year, although a complete summary of the WMO year 2001 Bulletins will be available soon. Suggestions concerning improving future Bulletins as well as comments on this years Bulletins should be sent to the email address given below.

6. Acknowledgements: These Bulletins use provisional data from the WMO Global Atmosphere Watch (GAW) stations operated within or near Antarctica by: Argentina (Comodoro Rivadavia, San Julian, Sobral, Ushuaia), Argentina/Finland (Marambio), Argentina/Italy/Spain (Belgrano), Australia (Macquarie Island), France (Dumont D'Urville and Kerguelen Island), Germany (Neumayer), Japan (Syowa), New Zealand (Arrival Heights), Russia (Mirny), Ukraine (Vernadsky), UK (Halley, Rothera), Uruguay (King George Island), and USA (South Pole). Satellite ozone data are also used and provided by NASA - Total Ozone Mapping Spectrophotometer (TOMS) and by the National Oceanic and Atmospheric Administration (NOAA) - TIROS Operational Vertical Sounder (TOVS). Potential vorticity maps are provided by ECMWF and their ERA-15 and daily T106 meteorological fields are analysed by the Norwegian Institute for Air Research (NILU) Kjeller, Norway, to provide vortex extent and extreme temperature information. Ozone data analyses are prepared in collaboration with the WMO World Ozone and Ultraviolet Data Centre in Toronto, Canada through the co-operation and support of the Meteorological Service of Canada (MSC). UV data is provided by the U.S. National Science Foundation's (NSF) UV Monitoring Network. Supporting graphics can be found at http://exp-studies.tor.ec.gc.ca/cgi-bin/selectMap (MSC) and http://www.nilu.no/projects/nadir/o3hole (NILU).

Questions regarding the scientific content of this Bulletin should be addressed to

Dr. Michael Proffitt, Senior Scientific Officer of WMO: e-mail proffitt@wmo.ch

END of WMO Antarctic Ozone Bulletin 8/2001





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