Zonal winds over the equator

Abstract

The dynamics of mean zonal flow over the Equator are described using a momentum budget. First the budget is drawn up for the troposphere, and the estimates of the mechanisms involved are shown to be consistent with the observed zonal wind/height profile. the technique is then applied to the stratosphere up to 30 km where the approximately 26‐month oscillation in zonal winds is observed. the necessity for a similar oscillation in the momentum convergence due to large‐scale horizontal eddies is deduced, and this oscillation is verified from wind observations. the vertical velocity/height profile associated with the zonal wind oscillation is derived and shown to be constant in time. the downward motion above 20 km and upward motion below is shown to be consistent with observed ozone and water vapour observations. Finally, types of synoptic systems are suggested which could be associated with the observed pattern of zonal flow and momentum convergence.