A Description of Local and Nonlocal Eddy-Mean Flow Interaction in a Global Eddying State Estimate

Abstract:

The assumption that local baroclinic instability dominates eddy-mean flow interactions is tested on a global scale using a dynamically consistent eddying state estimate. Interactions are divided into local and nonlocal. If all the energy released from the mean flow through eddy-mean flow interaction is used to support eddy growth in the same region, or if all the energy released from eddies through eddy-mean flow interaction is used to feed back to the mean flow in the same region, eddy-mean flow interaction is local; otherwise, it is nonlocal. Different regions have different characters: in the subtropical region studied in detail, interactions are dominantly local. In the Southern Ocean and Kuroshio and Gulf Stream Extension regions, they are mainly nonlocal. Geographical variability of dominant eddy-eddy, and eddy-mean flow processes is a dominant factor in understanding ocean energetics. This work points out the prevalence of eddy energy nonlocality and indicates the need of using nonlocal eddy parameterization schemes.