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

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 O 3 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 O 3 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.