Geographical Variability of the First Baroclinic Rossby Radius of Deformation

Abstract

Global 1° ? 1° climatologies of the first baroclinic gravity-wave phase speed c1 and the Rossby radius of deformation ?1 are computed from climatological average temperature and salinity profiles. These new atlases are compared with previously published 5° ? 5° coarse resolution maps of ?1 for the Northern Hemisphere and the South Atlantic and with a 1° ? 1° fine-resolution map of c1 for the tropical Pacific. It is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5%?15% owing to seemingly minor computational errors. Geographical variations in the new high-resolution maps of c1 and ?1 are discussed in terms of a WKB approximation that elucidates the effects of earth rotation, stratification, and water depth on these quantities. It is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and ?1 at any particular location in the World Ocean. This is rationalized from consideration of the WKB approximation.