Interannual variability in high latitude stratospheric ozone

We apply the principal component analysis (PCA) to the total column ozone data from the combined Merged Ozone Data (MOD) and European Center for Medium-Range Weather Forecasts (ECMWF) assimilated ozone. The interannual variability (IAV) of O3 in the high latitude is characterized by four main modes in Northern Hemisphere (NH) and Southern Hemisphere (SH). Attributable to dominant dynamical effects, these four modes account for nearly 60% and 75% of the total ozone variance in the NH and SH, respectively. In both hemispheres, the first two leading modes are nearly zonally symmetric and represent the connections to the Annular Modes and the Quasi-Biennial Oscillation. In particular, the leading mode in NH is characterized by a distinct 3.5-year period, and its secular variation may have contributed to the observed NH negative ozone trend from 1979 to 1994. The latter two modes exhibit in-quadrature, wavenumber-1 structures that represent the displacement of the polar vortex in response to planetary waves. In NH, these combined modes have preferred extrema location that suggests fixed topographical and land-sea thermal forcing of the involved planetary waves. Such stationary forcing is not apparent in the SH modes. For comparison, similar decompositions are performed for geopotential height layer thickness between 30 hPa and 100 hPa. Using these analyses, we find connections between the ozone and the dynamical variable.