Interannual Variability and Trends of Extratropical Ozone. Part II: Southern Hemisphere

Abstract

A principal component analysis (PCA) is applied to the Southern Hemisphere (SH) total column ozone following the method established for analyzing the data in the Northern Hemisphere (NH) in a companion paper. The interannual variability (IAV) of extratropical O3 in the SH is characterized by four main modes, which account for 75% of the total variance. The first two leading modes are approximately zonally symmetric and relate to the Southern Hemisphere annular mode and the quasi-biennial oscillation. The third and fourth modes exhibit wavenumber-1 structures. Contrary to the Northern Hemisphere, the third and fourth modes are not related to stationary waves. Similar results are obtained for the 30?100-hPa geopotential thickness. The decreasing O3 trend in the SH is captured in the first mode. The largest trend is at the South Pole, with value ??2 Dobson Units (DU) yr?1. Both the spatial pattern and trends in the column ozone are captured by the Goddard Earth Observation System chemistry?climate model (GEOS-CCM) in the SH.