North Atlantic Oscillation Changes and an Accelerated Recovery of Stratospheric Ozone in the Northern Hemisphere
Abstract
The relationship between North Atlantic Oscillation (NAO) changes and an accelerated recovery of polar stratospheric ozone in the northern hemisphere in the near future is investigated using four timeslice scenarios ("1960", "1980", "1990", "2015") of the interactively coupled chemistry-climate model E39/C. An extreme NAO index composite study of the winter seasons of the scenario ``1990'' and of the ECMWF reanalysis dataset of the period 1979-1993 shows the typical patterns associated with the NAO: in the positive phase the stratospheric polar vortex is stronger and colder than in the negative phase. In the troposphere, the high index conditions are marked by increased synoptic variance across the North Atlantic stormtrack whereas low index conditions are suggestive of blocking in the midtropospheric circulation. These patterns are associated with a reduced (enhanced) vertical propagation of stationary (transient) waves in the positive index winters. The mean model NAO index increases slightly from ``1960'' to ``1990'', and decreases more distinctly from ``1990'' to ``2015''. The NAO index changes are consistent with an enhanced vertical propagation of stationary waves and a dynamical warming of the northern hemisphere polar stratosphere in winter from ``1990'' to ``2015''. Thus, changes in tropospheric circulation regimes such as the NAO might be steering changes in stratospheric dynamics and hence ozone recovery in the northern hemisphere.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....3343S