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

Abstract

International audienceWe 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. © 2011 American Institute of Physics

Shock Modon: A New Type of Coherent Structure in Rotating Shallow Water

“…To test the robustness of the shock modons, we performed a number of simulations of their collisions, similar to our previous study [9]. They show that shock modons undergo frontal collisions forming either a new pair of shock modons after partner exchange, or a ''shock tripole'' with a fusion of anticylonic vortices.…”

“…Such ''shock modon'' appears as a result of relaxation of the QG modon with large Ro. As in our previous papers on ageostrophic modons [8], [9] we work with a newgeneration finite-volume code for RSW equations, which is well balanced (i.e., preserves equilibrium solutions) and entropy satisfying (i.e. guarantees the energy decrease across shocks) [10].…”

Existence and properties of ageostrophic modons and coherent tripoles in the two-layer rotating shallow water model on the -plane

“…The results presented above on the scattering of quasi-barotropic modons are not very different from what occurs in the barotropic one-layer model (Lahaye & Zeitlin 2011, 2012, which is due to the almost barotropic character of ageostrophic modons. The main difference is the trapped waves which appear in the baroclinic component in the two-layer case.…”

“…In previous studies with a one-layer model it was found that the AGMs survive frontal collision, forming two AGMs after exchange of partners (Ribstein et al 2010). Afterwards, we found that other collisions may produce new types of multipoles in the RSW model: the tripole (T) and the nonlinear ageostrophic modon (NAGM) (Lahaye & Zeitlin 2011). The former consists of an anticyclonic core with two cyclonic satellites, while the latter is a dipole with a reduced global Rossby number, because of larger distance between the two vorticity cores, and essentially nonlinear scatter plot of B versus PV (cf.…”

Evolution of double-eye wall hurricanes and emergence of complex tripolar end states in moist-convective rotating shallow water model

“…Such scatter plots are standard in diagnosing coherent structures of any nature in rotating shallow water models, cf. [23][24][25] and references therein. The structure in question is coherent if the points of the plot form a curve, as compared to a dispersed cloud in the opposite case.…”