Collisions of ageostrophic modons and formation of new types of coherent structures in rotating shallow water model

We study collisions of recently discovered ageostrophic modons in rotating shallow water model at different values of impact parameter and find that two new types of coherent vortex structures may be formed during this process: nonlinear modons, i.e., coherent dipoles with essentially nonlinear scatter plot and coherent tripoles. Both are known for incompressible 2D Euler equations, but were not reported in the compressible shallow water model. Inelastic scattering with strong filamentation and shearing is also possible. Surprisingly, the strongly nonlinear process of coherent structure formation leads to almost no emission of inertia-gravity waves. (C) 2011 American Institute of Physics. [doi:10.1063/1.3597608]