Dynamics and blocking of Rossby waves in quasi-two-dimensional shear flows

Abstract

One of the most intriguing phenomena in the Earth’s atmosphere—blocking of weather anomalies—is often attributed to the appearance of stationary or blocked Rossby waves in zonal flows. The Obukhov-Charney equation, which is the quasigeostrophic form of the potential vorticity transport equation, is traditionally used to describe Rossby waves in quasi-two-dimensional flows. A class of exact solutions of this equation that describes Rossby waves in the zonal flow with a constant horizontal shear has been constructed in this work. It has been shown that the features of wave dynamics fundamentally depend on the ratio of the wavelength to the radius of Rossby deformation. If this ratio is quite large, there is a fairly long-term quasistationary stage of evolution in which the meridional wavenumber and total energy of a wave (close to the maximum value) hardly depend on time. This effect is implemented under the conditions of the prevailing contribution of the deformation of the free surface of the atmosphere to potential vorticity. It has been shown that this effect can lead to new scenarios of the phase and amplitude blocking of Rossby waves.