Barotropic Instability with Divergence: Theory and Applications to Venus

Abstract

Infrared images of Venus reveal a curious double-lobed hot spot in the polar region. Elson has suggested that this ?dipole? represents a barotropic instability associated with a high-latitude jet. Unfortunately, the classical theory of barotropic instability cannot predict temperature variations. This paper generalizes the theory to include horizontal divergence, vertical motions, and temperature variations, and applies it to the stratosphere of Venus. The fastest-growing barotropic instability in the nominal model matches the observed dipole in period and horizontal temperature pattern. The accompanying wind variations are comparable to the speed of the mean jet indicating strong nonlinear effects. We conclude that the Venus dipole may represent the self-limited stage of a barotropic instability with divergence.