Zonal asymmetry of the Antarctic Oscillation

Abstract

In this research, the zonal asymmetry of the southern annular mode, or the Antarctic Oscillation (AAO), is studied. It is indicated that apparent zonal asymmetry exists in the normalized sea level pressure differences between the middle and high latitudes during the boreal summer, among different longitudes, especially between the Western and Eastern Hemispheres. Results show that the Southern Oscillation (SO) is responsible for part of the zonal asymmetry in AAO. The Western Hemisphere and the Eastern Hemisphere parts of AAO are correlated at 0.23 and 0.52 respectively for the period of 1959-1998 before and after the linear regressions on the Southern Oscillation Index (SOI) have been removed from the time series. The paper also discusses the relationship between the precipitation in the East Asia and the AAO before and after removing the linear regressions on SO index (SOI), indicating the stable relationship between the East Asian precipitation and the zonal symmetric component of AAOA. Copyright 2007 by the American Geophysical Union.