Baroclinic Eady Wave and Fronts. Part II: Geostrophic Potential Vorticity Dynamics in Semigeostrophic Space

Abstract

Abstract The geostrophic coordinate transformation is applied to the viscous semigeostrophic (SG) Eady wave. In the transformed space, called the SG space, the potential temperature anomaly can be treated as a delta-function anomaly of geostrophic potential vorticity (GPV) at the physical boundary or imaginary boundary (along the top of the boundary layer). Since the delta-function anomaly is analogous to the surface charge of a problem in electrostatics with the induced geopotential playing the role of the electric potential, the development of the Eady wave and fronts can be interpreted in terms of the interaction between the “surface charges” at two imaginary boundaries. It is shown that this interpretation and related GPV thinking for the viscous SG Eady wave can be made nearly as concise as its inviscid paradigm during the boundary stage (until the inviscid surface front collapses in physical space). When the viscous SG Eady wave develops into the interior stage, strong interior GPV anomalies, analog...