Low-frequency finite-amplitude oscillations in a near resonant topographically forced barotropic flow

摘要: Abstract In this paper, an inviscid, barotropic, nondivergent potential vorticity equation with topography in a β-plane channel is used to investigate nonlinear interaction between travelling Rossby wave uniform basic flow and single-wave the same zonal wavenumber. It found that for CDV-type monopole near resonance, when westerly wind resonant wind, 30–60 day low-frequency oscillations (LFO) can arise from wave-topography interaction. has both standing components. mid-latitudes (30°–45°N), westward-travelling LFO are dominated by Zonal Wavenumbers 1–3, while eastward-travelling 1 3. high latitudes (near 60°N), LEO observed travel westward, Wavenumber 1. However, LG-type (Legras Ghil, 1985) dipole resonance it requires weaker, more realistic flow. When be excited mid-bigh latitudes(30°–60°N), slowly either eastward or depending on intensity of 1–3. This demonstrates appears able induce finite-amplitude periods days Northern Hemisphere (NH) extratropics.