| Summary: | Breaking Rossby waves on the polar night vortex are numerically simulated by solving the 3D spherical primitive equations with the Spectral Element Atmospheric Model described in Part 1. A balanced axisymmetric-vortex is initialized with a step-function-like absolute-vorticity profile. Steadily-increasing, zonal-wavenumber-one surface-geopotential forcing is used to instigate upwardly propagating Rossby waves. Spurious reflection is prevented by a sponge layer near the model top. Isosurfaces of scaled potential vorticity exhibit complex dynamical features, e.g., a primary PV tongue, and a secondary instability causing roll-up into a ring of five smaller sub-vortices. These are shown in Figs. 3 and 4. These features converge, and PV gradients steepen, as resolution is increased. The PV-tongue-tip position, number of sub-vortices, zonal velocity profile and other quantitative measures are presented as specific modeling-accuracy results. SEAM produces solutions up to approximately T181 (approxi.
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