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On the relationship between total ozone and atmospheric dynamics and chemistry at mid-latitudes – Part 2: The effects of the El Niño/Southern Oscillation, volcanic eruptions and contributions of atmospheric dynamics and chemistry to long-term total ozone changes

by H. E. Rieder, L. Frossard, M. Ribatet, J. Staehelin, J. A. Maeder, S. Di Rocco, A. C. Davison, T. Peter, P. Weihs, F. Holawe show all authors
Atmospheric Chemistry and Physics Discussions ()

Abstract

We present the first spatial analysis of ``fingerprints{''} of the El\nNino/Southern Oscillation (ENSO) and atmospheric aerosol load after\nmajor volcanic eruptions (El Chichon and Mt. Pinatubo) in extreme low\nand high (termed ELOs and EHOs, respectively) and mean values of total\nozone for the northern and southern mid-latitudes (defined as the region\nbetween 30 degrees and 60 degrees north and south, respectively).\nSignificant influence on ozone extremes was found for the warm ENSO\nphase in both hemispheres during spring, especially towards low\nlatitudes, indicating the enhanced ozone transport from the tropics to\nthe extra-tropics. Further, the results confirm findings of recent work\non the connection between the ENSO phase and the strength and extent of\nthe southern ozone ``collar{''}. For the volcanic eruptions the analysis\nconfirms findings of earlier studies for the northern mid-latitudes and\ngives new insights for the Southern Hemisphere. The results provide\nevidence that the negative effect of the eruption of El Chichon might be\npartly compensated by a strong warm ENSO phase in 1982-1983 at southern\nmid-latitudes. The strong west-east gradient in the coefficient\nestimates for the Mt. Pinatubo eruption and the analysis of the\nrelationship between the AAO and ENSO phase, the extent and the position\nof the southern ozone ``collar{''} and the polar vortex structure\nprovide clear evidence for a dynamical `` masking{''} of the volcanic\nsignal at southern mid-latitudes. The paper also analyses the\ncontribution of atmospheric dynamics and chemistry to long-term total\nozone changes. Here, quite heterogeneous results have been found on\nspatial scales. In general the results show that EESC and the 11-yr\nsolar cycle can be identified as major contributors to long-term ozone\nchanges. However, a strong contribution of dynamical features (El\nNino/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO),\nAntarctic Oscillation (AAO), Quasi-Biennial Oscillation (QBO)) to ozone\nvariability and trends is found at a regional level. For the QBO (at 30\nand 50 hPa), strong influence on total ozone variability and trends is\nfound over large parts of the northern and southern mid-latitudes,\nespecially towards equatorial latitudes. Strong influence of ENSO is\nfound over the Northern and Southern Pacific, Central Europe and central\nsouthern mid-latitudes. For the NAO, strong influence on column ozone is\nfound over Labrador/Greenland, the Eastern United States, the\nEuro-Atlantic Sector, and Central Europe. For the NAO's southern\ncounterpart, the AAO, strong influence on ozone variability and\nlong-term changes is found at lower southern mid-latitudes, including\nthe southern parts of South America and the Antarctic Peninsula, and\ncentral southern mid-latitudes.

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