Abstract

Spacial and temporal changes in the mean field, due to the presence of finite-amplitude marginally un-stable and two neutral baroclinic waves, which form a resonant triad, are investigated in a quasi-geostrophic, inviscid, two-layer model on the beta plane. It is shown that the triad introduces, in each layer, mean horizontal Reynolds stresses which are responsible for a continuous north-south redistribution of the mean momentum in a vertical column. In the region π2/2½<F<10.5, where F represents the internal rotational Froude number, the time change of the mean zonal velocity in the upper layer is affected mainly by the divergence of the mean horizontal Reynolds stresses. In the region Fgt;10.5, it is affected strongly by both the horizontal component of the mean meridional circulation and the divergence of the mean horizontal Reynolds stresses. In the lower layer, in both regions of F, the time change of the mean zonal velocity is affected mainly by the horizontal component of the mean meridional circulation.

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