Eddy-zonal flow interactions associated with the southern hemisphere annular mode: Results from NCEP-DOE reanalysis and a quasi-linear model

Abstract

Using a recent 22-yr (1979-2000) record of the NCEP-Department of Energy (DOE) reanalysis 2 dataset (hereafter, NCEP2 reanalysis) and a two-level spherical quasi-geostrophic, quasi-linear model, the eddy-zonal-mean flow interactions associated with the Southern Hemisphere annular mode (SAM) variability have been investigated. The main emphasis is to highlight the differing natures of the eddy-zona-mean flow interactions (i) due to the high-frequency (2-8 days) eddies and medium-frequency (8-30 days) eddies, and (ii) during the extreme and transitional phases of the SAM. The results show that, in addition to a previously documented positive feedback due to the high-frequency eddies, the mediu..