Quasi-Biennial Cycles in Angular Momentum Transports at 500 mb

Abstract

Geostrophic angular momentum transport at 500 mb has been computed as a function of latitude and zonal wave number for a 10-yr period. The record has been inspected for evidence of periodic variations at latitudes 17.5N, 27.5N, 42.5N, and 57.5N. A quasi-biennial cycle is most prominent in the case of the planetary waves, with wave numbers 1 and 3 out of phase with wave number 2. The cyclone waves display a phase shift with time that implies a varying scheme of interaction with the long waves. Monthly average values of the 500-mb mean zonal wind, based on the same 10-yr record, do not indicate any strong periodicity.