Connections between low- and high- frequency variabilities of stratospheric northern annular mode and Arctic ozone depletion

Abstract

Previous studies have demonstrated a dynamical linkage between the ozone and stratospheric polar vortex strength, but only a few have mentioned the persistence of the anomalous vortex. This study uses the complete ensemble empirical mode decomposition with adaptive noise to decompose the winter stratospheric northern annular mode (NAM) variabilities into relatively low frequencies (>4 months) and high frequencies (<2 months) (denoted as NAM _L and NAM _H ) and investigates their relationship with the Arctic ozone concentration in March. A closer relationship is found between the Arctic ozone and the NAM _L , i.e. a persistently strong stratospheric polar vortex in winter (especially February–March) is more critical than a short-lasting extremely strong vortex in contributing to Arctic ozone depletion. We find that a negative NAM _H or major stratospheric sudden warming event in early winter could be a precursor for the anomalous depletion of Arctic ozone in March. The NAM _L changes are further related to the warm North Pacific sea surface temperature (SST) anomalies and ‘central-type’ El Niño-like or La Niña-like SST anomalies in early winter months, as well as cold North Atlantic SST anomalies and higher sea ice concentration in the Barents–Kara Sea from late-autumn to early-spring.

Keywords

• ozone depletion
• northern annular mode
• stratospheric polar vortex
• low and high frequency variability