Mesoscale characteristics

Abstract

The spatial length, time, and propagation characteristics of the ocean mesoscale variability are examined throughout the globe. Sea surface height (SSH) variations from a combination of the Geosat Exact Repeat Mission, ERS‐1, ERS‐2, and TOPEX/Poseidon altimeter satellites are used to compute the observed covariance of the mesoscale. The mesoscale is defined as the residual SSH after removing a filtered large‐scale SSH having length scales greater than 750 km zonally and 250 km meridionally. From the observed binned covariance function, an objective analysis computes characteristics of the climatological mesoscale variability. Westward propagation is dominant throughout the globe. The Antarctic Circumpolar Current appears to affect the zonal propagation, as the propagation direction is eastward throughout this current. Length scales and propagation speeds generally decrease away from the equator and are slightly larger in the west basin areas than in the east basin areas. Zonal propagation speeds are roughly in agreement with speeds based on linear quasi‐geostrophic dynamics. The eddy field diverges from the equator and converges at 15° in the Northern and Southern Hemispheres. Requirements for synoptic mesoscale observation are examined.