Detecting "dipole ring" separatrices with zebra palettes

Two new analysis methods applicable to remote sensing of the sea surface are described. The first is a zebra false-color palette that combines a slowly varying rainbow with a rapid gray-scale sinusoid, and the other is a routine that tracks the thermal separatrix, or dividing line, between two (of more) circulation regimes. Used together, a significant increase in data retention is achieved compared to traditional algorithms based on frontal digitizations. These two methods are applied to historical infrared data of Gulf Stream rings from the western North Atlantic. The ring data indicate anticyclonic rings usually have at least one cyclonic companion and are more appropriately modeled as dipoles. Several examples of cyclonic rings in the Sargasso Sea are seen with anticyclonic companions and are also believed to be dipoles. The separatrix method is shown to provide reliable rotation rates for these vortex systems.