EQUATORIAL OSCILLATIONS MAINTAINED BY GRAVITY-WAVES AS DESCRIBED WITHTHE DOPPLER SPREAD PARAMETERIZATION - II - HEURISTIC ANALYSIS

The Doppler Spread Parameterization (DSP) for gravity waves (GW) devel oped by Hines is applied to the zonal momentum budget at the equator. For sufficiently large oscillation amplitudes in the background zonal winds, comparable to the GW induced wind variability, the momentum sou rce is intermittent and as such it represents a nonlinearity of third or generally odd order. This kind of nonlinearity generates, besides h igher harmonics, the fundamental harmonic itself which is retained in a simplified analytical solution that can describe self-sustained osci llations without invoking external, time dependent forcing. The formul ation is discussed to provide some understanding of the numerical resu lts presented in the companion paper. (C) 1998 Elsevier Science Ltd.