Interannual variations in the half-yearly cycle of pressure gradients and zonal wind at sea level on the Southern Hemisphere

We outline the half-yearly oscillations in sea-level pressure gradients and zonal winds on the Southern Hemisphere by means of daily synoptic maps for several years. The pressure oscillation has amplitude peaks near 50°S and the Antarctic coast, separated by a minimum along 60°S where the phase changes from maxima in the extreme seasons in the south to maxima in the transitional season in the north. The zonal geostrophic wind consequently has a half-yearly wave with equinoctial maxima in the latitudes near 60°S, and one with solstitial maxima north of 50°S.

We describe the interannual variability of the half-yearly oscillations in the pressure gradients and winds, and give examples of the oscillations during FGGE and the IGY.