Baroclinic wave packets in an extended quasigeostrophic two-layer model

Abstract

An extended quasigeostrophic two-layer model including nonlinear Ekman pumping and nonlinear interface perturbation is used to numerically study the formation and maintenance of baroclinic wave packets. With an initial zonal jet flow of north-south symmetry and small random initial perturbations wave packets of finite amplitude are produced and maintained with an equilibrated wave packet-zonal flow system exhibiting simultaneously downstream-upstream asymmetry and north-south asymmetry, the later of which has not been observed in the past simple quasigeostrophic two-layer modeling studies. The northern upstream part of the wave packets is stronger than its southern upstream counterpart and therefore the peak of time-and-zonal-average eddy kinetic energy associated with the wave packets is shifted poleward while the peak of the time-mean zonal jet flow is shifted equatorward, which is in agreement with the observations. Copyright 2007 by the American Geophysical Union.