The buoyancy staircase limit in surface quasigeostrophic turbulence

Surface buoyancy gradients over a quasigeostrophic fluid permit the existence of surface-trapped Rossby waves. The interplay these waves with surface turbulence results in latitudinally inhomogeneous mixing that, under certain conditions, culminates staircase: meridional profile consisting mixed zones punctuated by sharp gradients, eastward jets centred at and weaker westward flows between. In this article, we investigate emergence staircase limit examine dependence resulting dynamics on vertical stratification. Over decreasing stratification ( $\mathrm {d}N(z)/\mathrm {d}z\leq 0$ , where $N(z)$ is frequency), obtain longer interaction range (than uniform stratification) highly dispersive limit, find straight that are perturbed propagating along jet waves, similar to two-dimensional barotropic $\beta$ -plane turbulence. contrast, increasing {d}z\geq ), shorter weakly sinuous large latitudinal meanders whose shape evolves time due propagation These have larger amplitudes than stratification, and, as result, ratio domain-averaged zonal speeds two three times smaller Finally, for given Rhines wavenumber, closer together