Mesoscale characteristics

The spatial length, time, and propagation characteristics of the ocean meso scale variability are examined throughout the globe. Sea surface height (SS H) variations from a combination of the Geosat Exact Repeat Mission, ERS-1, ERS-2, and TOPEX/Poseidon altimeter satellites are used to compute the obs erved 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 kin meridionally. From the observed binned cov ariance function, an objective analysis computes characteristics of the cli matological mesoscale variability. Westward propagation is dominant through out the globe. The Antarctic Circumpolar Current appears to affect the zona l propagation, as the propagation direction is eastward throughout this cur rent. Length scales and propagation speeds generally decrease away from the equator and are slightly larger in the west basin areas than in the east b asin areas. Zonal propagation speeds are roughly in agreement with speeds b ased on linear quasi-geostrophic dynamics. The eddy field diverges from the equator and converges at 15 degrees in the Northern and Southern Hemispher es. Requirements for synoptic mesoscale observation are examined.