The September 2002 Antarctic vortex major warming as observed by visible spectroscopy and ozone soundings

Abstract

The record of O₃ total column and NO₂ obtained by visible spectroscopy at Ushuaia (55° S), Marambio (64° S) and Belgrano (78° S) and vertical ozone profiles from the latter station provide insight into the unprecedented major warming observed above Antarctica in the last week of September 2002. From 18 September to 25 September the temperature increased 54°C at the isentropic level of 700 K. The temperature anomaly was observed down to the level of 300 K in which a well‐defined tropopause was established. From comparison of the ozone profiles before and during the event, it can be seen that a fast increase in O₃ took place basically above 500 K, but the layer where the ozone hole occurs was barely affected. Low potential vorticity values above Belgrano occurred only at levels above 500 K, confirming that the vortex split was confined to heights above the layer of the Antarctic spring depletion. The signature of poleward‐transported air is clearly visible from the NO₂ column departure from the envelope of the previous years in all three stations. NO₂ columns larger than typical for ozone hole conditions by 400% were observed at Belgrano. Diurnal variations provide evidence of non‐denitrified extra‐vortex air.

Acknowledgements

This work has been funded partially by the Spanish Antarctic Programme (ANT97‐0433, REN2000.0245‐C02/01) and the European Union through the project QUILT (EVK2‐2000‐00545). The logistical support of the Spanish Marine Technology Unit (MTU) is gratefully acknowledged. Many thanks to all operational teams at the stations. The ECMWF temperature and potential vorticity data were provided by the Norwegian Institute for Air Research (NILU) database. The authors also thank Eberhard Reimer (FU Berlin, Germany) and Holger Deckelmann (AWI, Potsdam) for trajectory calculations.