Troposphere–stratosphere communication through local vertical waveguides

Abstract

The effects of zonally non-uniform background flow on the three-dimensional propagation of extratropical Rossby waves are examined using the WKB (Wentzel-Kramers-Brillouin) formalism. Emphasis is placed on the vertical propagation of wave activity. An extended Charney-Drazin (CD) condition that is valid for zonally non-uniform background flow is derived. The extended CD condition shows that local vertical propagation (trapping) is possible for wave scales for which the traditional CD condition predicts trapping (propagation). Local vertical propagation is shown to be strongly dependent on the phasing of the wave source relative to the background flow. Specifically, in zonally non-uniform background flow, vertical propagation is confined to local vertical waveguides whose formation is controlled by the orientation of the background wind relative to the wave fronts. Within the waveguide, vertical propagation is optimized when the disturbance wind field is parallel to the background potential vorticity gradient. As the wave packets move from the tropospheric source into the stratosphere they expand in zonal scale. The implications of these results to stratospheric sudden warmings are discussed.

Madden‐Julian Oscillation in a climate model with a well‐resolved stratosphere

“…The localized interactions away from the equator, illustrated in Figure 8, are qualitatively consistent with the linear theory for vertical propagation in complex three‐dimensional background fields recently developed on a beta plane and demonstrated with idealized flows [ Nathan and Hodyss , 2010]. This theory shows that vertical propagation is possible over limited longitudes even where the classical theory of Charney and Drazin [1961] precludes propagation in zonally averaged flows.…”

Geographical Dependence Observed in Blocking High Influence on the Stratospheric Variability through Enhancement and Suppression of Upward Planetary-Wave Propagation

“…1a), with their potential to act as strong sources of upward-propagating Rossby wave packets. It may also arise from the tendency for those wave packets to propagate upward effectively through a zonally confined vertical waveguide that reflects the three-dimensional structure of the climatological-mean PWs (Nishii and Nakamura 2004;Nathan and Hodyss 2010).…”

Role of wave–mean flow interaction in sun–climate connections: Historical overview and some new interpretations and results

“…To show in conceptual terms the connection between solar-modulated wave propagation and attenuation and the divergence of the EP flux, we use the quasi-geostrophic framework. We assume the zonally uniform background flow is slowly varying, which permits a steady-state, phase-integral (WKB) solution for the disturbance streamfunction field of the form (Nathan and Hodyss, 2010),…”