Interannual Variability and Trends of Extratropical Ozone. Part I: Northern Hemisphere

Abstract

The authors apply principal component analysis (PCA) to the extratropical total column ozone from the combined merged ozone data product and the European Centre for Medium-Range Weather Forecasts assimilated ozone from January 1979 to August 2002. The interannual variability (IAV) of extratropical O 3 in the Northern Hemisphere (NH) is characterized by four main modes. Attributable to dominant dynamical effects, these four modes account for nearly 60% of the total ozone variance in the NH. The patterns of variability are distinctly different from those derived for total O 3 in the tropics. To relate the derived patterns of O 3 to atmospheric dynamics, similar decompositions are performed for the 30-100-hPa geopotential thickness. The results reveal intimate connections between the IAV of total ozone and the atmospheric circulation.The first two leading modes are nearly zonally symmetric and represent the connections to the annular modes and the quasi-biennial oscillation. The other two modes exhibit in-quadrature, wavenumber-1 structures that, when combined, describe the displacement of the polar vortices in response to planetary waves. In the NH, the extrema of these combined modes have preferred locations that suggest fixed topographical and land-sea thermal forcing of the involved planetary waves. Similar spatial patterns and trends in extratropical column ozone are simulated by the Goddard Earth Observation System chemistry-climate model (GEOS-CCM).The decreasing O 3 trend is captured in the first mode. The largest trend occurs at the North Pole, with values ϳϪ1 Dobson Unit (DU) yr Ϫ1. There is almost no trend in tropical O 3 . The trends derived from PCA are confirmed using a completely independent method, empirical mode decomposition, for zonally averaged O 3 data. The O 3 trend is also captured by mode 1 in the GEOS-CCM, but the decrease is substantially larger than that in the real atmosphere.

Aura Microwave Limb Sounder observations of the polar middle atmosphere: Dynamics and transport of CO and H2O

“…The second and third modes of the NAM, SAM, CNAM, and CSAM can be viewed as a pair of wave 1 patterns with the orthogonal orientation rotating slightly with altitude. Similar ranking of EOF patterns has been noted in NH column ozone [ Jiang et al , 2008]. For the HNAM and HSAM (Figures 2c–2e and 3c–3e), the second EOFs have an annular pattern at high latitudes transitioning to a wave 1 pattern at midlatitudes.…”

Aura Microwave Limb Sounder observations of the Northern Annular Mode: From the mesosphere to the upper troposphere

“…Not well separated, these two modes are ranked consistently at all altitudes in the second and third place in terms of variance contribution. Similar rank has been noted in third and fourth modes of NH column ozone [Jiang et al, 2008]. Details of the first and second modes in the troposphere and the stratosphere, and the (1948 -2008) are also shown at 50 hPa and 300 hPa.…”

The influence of tropospheric biennial oscillation on mid-tropospheric CO2

“…The two‐year signal in the deseasonalized and detrended mid‐tropospheric CO 2 may be related to the TBO. The statistical significance of signals in the power spectrum was obtained by comparing the amplitude of a spectral peak to the mean red noise spectrum [ Gilman et al , 1963; Jiang et al , 2008b].…”