The robustness of self-organized zonal jets in unforced, turbulent vorticity fields

Program in Applied Mathematics and Department of Applied Physics Columbia University, New York, NY 10027, USA

Abstract

A wide parameter space is spanned to check the influence of numerical parameters on self-organized jets in rotating, turbulent shallow-water flows. It is found that, even in harsh physical (strongly ageostrophic) and numerical (filtered, hyperviscous, high-resolution) environments, the basic morphogenesis of steady jets, qualitatively reflecting the Rhines scale, is robust. However, detailed features of the jet pattern, such as the amplitude, the width, and the location can be substantially affected by numerical parameters for a fixed set of physical parameters. In general, while the amount of energy lost seems to be a good predictor of maximum jet amplitude and width, a nonmonotonic dependence of these features on the numerical parameters is observed. The most acute sensitivity is associated with the use of a hyperdissipation operator in conjunction with a Robert-Asselin filter, which leads to substantial meridional shifts of the entire jet pattern as the viscosity coefficient is varied.