Rings in numerical models of ocean general circulation: A statistical study

Because of their importance in the ocean energetics and general circulation, a proper representation of ring generation mechanisms and evolution in numerical models is crucial for an accurate picture of the heat, salt, and energy budgets. Ring locus, lifetime, propagation speed, radius, and interface displacement statistics are derived for four widely used eddy‐resolving numerical models and compared to the 10‐year statistical analysis of Gulf Stream rings based on time series of satellite infrared determinations performed by Brown et al. (1986). The ring formation process and behavior in ocean numerical models depends upon the governing equations, the vertical coordinate, and the boundary conditions used. It is shown that as more terms are retained in the model equations, the mid‐latitude jet becomes more unstable, and its interior penetration as well as the associated number of rings formed are reduced. Rings in the layer model have slower propagation speeds and longer lifetimes than their level counterparts. Such results illustrate the sensitivity of numerical ocean circulation models to the physical and numerical assumptions made.