A numerical simulation of amplification of low-frequency planetary waves and blocking formations by the upscale energy cascade

Results of nonlinear simulations of the amplification of LF planetary waves and concurrent blocking formations are presented. The simulations are conducted by a barotropic spectral model derived form 3D spectral primitive equations with a basis of vertical structure functions and Hough harmonics. The analysis of the energetics of blocking formations in the model showed an amplification of the meridional dipole model confirmed by means of the upscale energy cascade from synoptic disturbances under an environment of persistently amplified wavenumber 2. When the persistent wavenumber 2 exists, synoptic disturbances contribute to amplify the dipole mode of wavenumber 1. When the persistent wavenumber 2 is absent, synoptic disturbances contribute to accelerate zonal flow with enhanced wave-mean flow interactions, and wavenumber 1 is not amplified. It is concluded that the persistent wavenumber 2 plays a catalytic role in drawing synoptic wave energy and feeding wavenumber 1.