Vertical propagation of planetary waves in the stratosphere through a zonally asymmetric basic state

Vertical propagation of stratospheric planetary waves through a zonally asy mmetric basic state is investigated in a simplified numerical model for und erstanding co-existence effects of zonal wavenumber 1 and 2. We compare wave solutions in a zonally asymmetric basic flow with those in a pure zonal flow. The differences are considered from a view of potential vorticity (PV) distribution, to find that the zonally asymmetric basic flow has an effect of the zonal modulation of PV induction by local westerlies associated with the wave. As a result, a component forced at the bottom bou ndary in the zonally asymmetric flow departs from that in the zonally symme tric flow, and components unforced appear. Detailed behaviors of each wave component in the zonally asymmetric flow depend on the phase relation betwe en the distorted basic flow and the bottom forcing.