Relationship between North Atlantic Oscillation changes and stratospheric ozone recovery in the Northern Hemisphere in a chemistry‐climate model

Abstract

The relationship between North Atlantic Oscillation (NAO) changes and northern stratospheric ozone recovery in the near future is investigated using four timeslice scenarios (1960, 1980, 1990, 2015) of the chemistry‐climate model ECHAM4.L39(DLR)/CHEM. A wintertime NAO index composite study of the scenario “1990” and of the ECMWF reanalyses shows the typical NAO patterns: in the positive phase the stratospheric polar vortex is stronger and colder than in the negative phase. In the troposphere, the positive phase is marked by increased variance across the North Atlantic stormtrack whereas the negative phase is suggestive of blocking. Consistently, vertical stationary (transient) wave propagation is reduced (enhanced) in the positive phase. The model NAO index decreases significantly from “1990” to “2015”. This coincides with enhanced vertical stationary wave propagation and a dynamical heating of the northern polar stratosphere. Thus, tropospheric circulation changes might influence stratospheric dynamics and hence northern hemisphere ozone evolution.