A formulation of a wave-activity flux for stationary Rossby waves on a zonally varying basic flow
Article first published online: 7 DEC 2012
Copyright 1997 by the American Geophysical Union.
Geophysical Research Letters
Volume 24, Issue 23, pages 2985–2988, 1 December 1997
How to Cite
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Accepted: 21 OCT 1997
- Manuscript Received: 30 MAY 1997
A new formulation of an approximate conservation relation is proposed for stationary Rossby waves on a zonally varying basic flow, utilizing that A (proportional to wave enstrophy) and ε (proportional to wave energy) are both related to the wave activity pseudomomentum. For stationary Rossby waves, it is shown in the limit of a small-amplitude, plane wave on a slowly varying, unforced non-zonal flow that a particular linear combination of A and ε, namely, M ≡ (A + ε)/2, is independent of the wave phase, even if unaveraged, and is conserved under steady, unforced and nondissipative conditions. It is also shown that the three-dimensional flux of M is parallel to the local group velocity in the WKB limit. The flux could be a useful diagnostic tool, as shown in an example that presents a “snapshot” of the three-dimensional propagation of a stationary Rossby wavetrain in the real atmosphere. Our conservation relation is a generalization of that for stationary Rossby waves on a zonally-uniform basic flow derived by Plumb.