Stratospheric planetary flows from the perspective of the Euler equation on a rotating sphere

TL;DR

This paper investigates stationary solutions of Euler's equation on a rotating sphere, their stability, and their role in modeling stratospheric planetary flows, revealing conditions for rigidity, stability criteria, and bifurcation phenomena.

Contribution

It establishes rigidity results, stability criteria, and bifurcation analysis for stationary solutions of Euler's equation on a rotating sphere, linking them to stratospheric flow dynamics.

Findings

Rigidity results ensure solutions are zonal or rotated zonal.

An analogue of Arnold's stability criterion is proved.

Stationary solutions serve as building blocks for stratospheric flow models.

Abstract

This article is devoted to stationary solutions of Euler's equation on a rotating sphere, and to their relevance to the dynamics of stratospheric flows in the atmosphere of the outer planets of our solar system and in polar regions of the Earth. For the Euler equation, under appropriate conditions, rigidity results are established, ensuring that the solutions are either zonal or rotated zonal solutions. A natural analogue of Arnold's stability criterion is proved. In both cases, the lowest mode Rossby-Haurwitz stationary solutions (more precisely, those whose stream functions belong to the sum of the first two eigenspaces of the Laplace-Beltrami operator) appear as limiting cases. We study the stability properties of these critical stationary solutions. Results on the local and global bifurcation of non-zonal stationary solutions from classical Rossby-Haurwitz waves are also obtained. Finally, we show that stationary solutions of the Euler equation on a rotating sphere are building blocks for travelling-wave solutions of the 3D system that describes the leading order dynamics of stratospheric planetary flows, capturing the characteristic decrease of density and increase of temperature with height in this region of the atmosphere.