Dynamics of Low-Frequency Variability: Barotropic Mode

Abstract

The dynamics of low-frequency variability is investigated in terms of sensitivity to the dependence of its relative zonal position of a single storm track in a simplified global circulation model. A streamfunction tendency equation is derived that explicitly distinguishes between barotropic and baroclinic components. One of the two low-frequency patterns located in the center of the storm track grows barotropically, and its decay is accomplished by low-frequency eddy vorticity fluxes and the baroclinic contribution to the divergence term. The growth and decay of the second pattern, located at the downstream end of the storm track, is dominated by nonlinear processes. This indicates that the dynamical processes leading to growth and decay of low-frequency patterns depend on the zonal position of the low-frequency pattern relative to a storm track.