The role of transient eddies in low‐frequency zonal variations of the Southern Hemisphere circulation

Abstract

The dominant modes of low‐frequency variation of the Southern Hemisphere (SH) circulation in winter have been identified using 15 years of monthly mean analyses of the SH troposphere. The two leading modes are primarily zonally‐symmetric, representing out‐of‐phase variations of geopotential height between middle and high latitudes in one case and between the tropics and middle latitudes in the other. There are accompanying variations of zonal wind and temperature associated with these modes, which have an equivalent barotropic vertical structure in the extratropics. The two modes represent 25% of the variance of the monthly mean height in the SH. The high‐latitude mode is also the dominant p..