Baroclinic topographic modons

The theory of solitary topographic Rossby waves (modons) in a uniformly rot ating two-layer ocean over a constant slope is developed. The modon is desc ribed by an exact, form-preserving, uniformly translating, horizontally loc alized, nonlinear solution to the inviscid quasi-geostrophic equations. Bar oclinic topographic modons are found to translate steadily along contours o f constant depth in both directions: either with negative speed (within the range of the phase velocities of linear topographic waves) or with positiv e speed (outside the range of the phase velocities of linear topographic wa ves). The lack of resonant wave radiation in the first case is due to the o rthogonality of the flow field in the modon exterior to the linear topograp hic wave field propagating with the modon translation speed, that is imposs ible for barotropic modons. Another important property of a baroclinic topo graphic modon is that its integral angular momentum must be zero only in th e bottom layer; the total angular momentum can be non-zero unlike for the b eta-plane modons over flat bottom. This feature allows modon solutions supe rimposed by intense monopolar vortices in the surface layer to exist. Expli cit analytical solutions for the baroclinic topographic modons with piecewi se linear dependence of the potential vorticity on the streamfunction are p resented and analysed.