Two-layer geostrophic tripoles comprised by patches of uniform potential vorticity

The so-called carousel tripoles are constructed and characterized in the framework of two-layer quasi-geostrophic contour dynamics, and their stability is examined. Such a tripole is a steadily rotating doubly symmetric ensemble of three collinear vortices, or more specifically, uniform-potential-vorticity patches, with the central, core vortex, located in the upper layer, and the two remaining, satellite vortices, in the lower layer, or vice versa. The carousel tripole solutions are obtained with the use of a numerical iterative procedure. A tripole with zero total potential vorticity can be generally identified by a point in the plane spanned by two parameters, namely, the typical size of the patches relative to the Rossby deformation radius, and some shape parameter. We consider two kinds of the parameter plane by taking as the second parameter either the distance d between the centroids of the core and one of the satellites (termed also separation) or, alternatively, the minimal distance h between the...