現実的な地形が入った順圧モデル大気の応答と定常解の多重性の可能性

Abstract

The response of flow in a barotropic, β-plane, channel model atmosphere with the external forcing due to realistic topography is examined by making use of spectral expansion of physical variables in wavenumber space. In the model planetary waves are excited by zonal flow over the topographic perturbations while the fluctuation of zonal flow is influenced by the planetary waves through the form-drag of topography.In the case where nonlinear interactions between planetary waves are absent stationary solution can be obtained analytically and its dependency on parameters such as meridional channel width, dissipation rate for waves and zonal flow is studied. It is revealed that for plausible range of parameters describing real atmosphere a multiplicity of stationary solution cannot be readily realized.In the case including nonlinearity of wave-wave interactions the deviation of response of flow from the stationary solutions determined in the former case is examined by numerical experiments as a nonstationary problem. A meandering solution corresponding to blocking situation which is expected to exist as one of multiple stationary solutions for rather small dissipation rate is found to be feeble to nonlinear interactions between waves and to change into another stationary or quasi-periodic state.