Low-Frequency Variability in the Midlatitude Atmosphere Induced by an Oceanic Thermal Front

Abstract

This study examines the flow induced in a highly idealized atmospheric model by an east-west-oriented oceanic thermal front. The model has a linear marine boundary layer coupled to a quasigeostrophic, equivalentbarotropic free atmosphere. The vertical velocity at the top of the boundary layer drives the flow in the free atmosphere and produces an eastward jet, parallel to the oceanic front's isotherms. A large gyre develops on either side of this jet, cyclonic to the north and anticyclonic to the south of it. As the jet intensifies during spinup from rest, it becomes unstable. The most unstable wave has a length of about 500 km, it evolves into a meander, and eddies detach from the eastern edge of each gyre.