Study Of Rossby Solitary Wave Evolution Model Under Nonlinear Barotropic-baroclinic Coherent Structure

In large-scale motions,the atmospheric and oceanic motions manifest as nonlinear Rossby isolated waves,and isolated waves are important to explaining practical problems because they can keep the amplitude structure unchanged.In this paper,we study the evolution mechanism of nonlinear barotropic-baroclinic interaction of large-scale atmospheric and oceanic motions,especially the excitation,propagation to dissipation of nonlinear Rossby wave amplitude coherent structure is discussed in depth.Starting from the classical two-level quasi-geostrophic model equations,the coupled nonlinear Korteweg-de Varies model equations for the evolution of the barotropic and baroclinic coherent structures are obtained by introducing the barotropic flow function and the baroclinic flow function,and considering the effects of bottom topography and the -plane approximation on them,using the multiple scaling method and the regressive expansion method,respectively.The Jacobi elliptic function expansion method is used to solve the solitary wave solutions of coupled nonlinear Korteweg-de varies model equations,and the physical mechanism of the nonlinear barotropic-baroclinic coherent structure evolution is analyzed qualitatively based on the obtained solitary wave solution.Through the numerical method,the effect is quantitatively analyzed to excite and propagate the barotropic or baroclinic solitary wave coherent structure more at high latitudes,and the nonlinear propagation of barotropic and baroclinic solitary wave structure is enhanced by larger barotropic fundamental background flow and topographic slope.And the structural changes of dipole in each flow field are discussed according to the flow field distribution.It provides the necessary theoretical basis of revealing and understanding the physical mechanism of atmospheric obstruction phenomenon or wave flow action.