Global characteristics of coherent eddies from drifter trajectories

An analysis of looping surface drifter trajectories is performed using Global Drifter Program data. First, a methodology is developed to identify when drifters begin and end coherent submesoscale-to-mesoscale looping, which more closely matches Richardson's [1993] definition of a "looper" than more recent, automated efforts such as Griffa et al. [2008]. Analysis of the resulting data set of loopers indicates the substantially higher EKE of loopers, the dominance of cyclonic or anticyclonic vorticity in various regions, the size and period of the looping trajectories, and the fact that the mean displacements of loopers is often substantially different than the mean displacements of nonloopers.