Coupled Interannual Rossby Waves in a Quasigeostrophic Ocean–Atmosphere Model

Abstract

Rossby wave propagation is investigated in the framework of an idealized middle-latitude quasigeostrophic coupled ocean-atmosphere model. The Rossby waves are observed to propagate faster than both the classical linear theory (unperturbed solution) and the phase speed estimates when the effect of the zonal mean flow is added (perturbed solution). Moreover, using statistical eigentechniques, a clear coupled Rossby wave mode is identified between a baroclinic oceanic Rossby wave and an equivalent barotropic atmospheric wave. The spatial phase relationship of the coupled wave is similar to the one predicted by Goodman and Marshall, suggesting a positive ocean-atmosphere feedback. It is argued that oceanic Rossby waves can be efficiently coupled to the overlying atmosphere and that the atmospheric coupling is capable of adding an extra speedup to the wave; in fact, when the ocean is simply forced, the Rossby wave propagation speed approaches the perturbed solution.

Empirical Evidence Linking the Pacific Decadal Precession to Kuroshio Extension Variability

“…Importantly, these two characteristics subsequently allow the anomalies to continue to force the initial SSH anomaly (Figures 3e and 3f). Through the time integration of this forcing (Frankignoul et al, 1997;Kwon et al, 2010;Qiu et al, 2007), the resultant baroclinic Rossby wave intensifies as it propagates westward (Farneti, 2007;Yi et al, 2015), which is also a characteristic seen in our empirical analysis (Figures 4e and 4f). As the SSH anomaly passes the date line, our empirical analysis indicates that it narrows substantially as it approaches the western portion of the basin (Figure 4g), consistent with the transition from large-scale, linear Rossby wave dynamics to mesoscale, non-linear Rossby wave dynamics along a jet (Sasaki et al, 2014).…”

“…This propagation of the meridional dipole in atmospheric pressures is co‐located with a similar propagating dipole in SSTs (Figures e, f, and ) and is equivalent barotropic with higher‐than‐normal atmospheric pressures situated over warmer‐than‐normal SSTs. As noted above, previous theoretical results (Goodman & Marshall, ; Ferreira et al, ; Farneti, ; Fang & Yang, ) highlight that this equivalent barotropic structure can sustain the oceanic and atmospheric anomalies through positive feedbacks in which the wind stress curl associated with the atmospheric anomaly induces changes in SSTs via vertical and horizontal advection (Farneti, ; Yi et al, ; Kwon et al, ; Qiu et al, ; Fang & Yang, , ). By altering the large‐scale meridional temperature gradient, the SST anomalies in turn modify the baroclinicity of the overlying atmosphere and give rise to anomalous transient eddy activity that sustains the large‐scale, low‐frequency atmospheric anomalies through vorticity flux convergence (Fang & Yang, ; Kushnir et al, ; Lau & Nath, ; Xue et al, ; Zhou et al, ).…”

Fast and slow resonant triads in the two-layer rotating shallow water equations

“…This involves modelling the interaction between two active layers with simulated dynamics, as opposed to having a passive atmosphere and dynamic ocean. Later work by Farneti (2007) showed results in a numerical climate model close to those predicted by the coupling model, using an active upper layer. These papers build up a picture of climate modelling requiring contributions from many scales and particularly highlight the importance of interactions between layers: there is a need for work that investigates these effects.…”

Predicting El Niño Beyond 1-year Lead: Effect of the Western Hemisphere Warm Pool

“…2a ). Meanwhile, the SST cooling and the suppressed precipitation over the subtropical North Pacific induce an anomalous anticyclone to the west according to the off-equatorial Gill response and atmosphere–ocean interaction in the subtropics 37 . The enhanced northerly wind anomalies associated with the anomalous anticyclone further strengthen the negative MSE advection and associated precipitation anomalies.…”