Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed

The horizontal gradient of potential vorticity (PV) across the tropopause typically declines with lead time in global numerical weather forecasts and tends towards a steady value dependent on model resolution. This paper examines how spreading the tropopause PV contrast over a broader frontal zone affects the propagation of Rossby waves. The approach taken is to analyse Rossby waves on a PV front of finite width in a simple single-layer model. The dispersion relation for linear Rossby waves on a PV front of infinitesimal width is well known; here, an approximate correction is derived for the case of a finite-width front, valid in the limit that the front is narrow compared to the zonal wavelength. Broadening the front causes a decrease in both the jet speed and the ability of waves to propagate upstream. The contribution of these changes to Rossby wave phase speeds cancel at leading order. At second order the decrease in jet speed dominates, meaning phase speeds are slower on broader PV fronts. This asymptotic phase speed result is shown to hold for a wide class of single-layer dynamics with a varying range of PV inversion operators. The phase speed dependence on frontal width is verified by numerical simulations and also shown to be robust at finite wave amplitude, and estimates are made for the error in Rossby wave propagation speeds due to the PV gradient error present in numerical weather forecast models.

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Coupled Interannual Rossby Waves in a Quasigeostrophic Ocean–Atmosphere Model

Journal of Physical Oceanography ◽

10.1175/jpo3061.1 ◽

2007 ◽

Vol 37 (5) ◽

pp. 1192-1214 ◽

Cited By ~ 4

Author(s):

Riccardo Farneti

Keyword(s):

Wave Propagation ◽

Rossby Wave ◽

Rossby Waves ◽

Phase Relationship ◽

Phase Speed ◽

Middle Latitude ◽

Mean Flow ◽

Ocean Atmosphere ◽

Rossby Wave Propagation ◽

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.

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Rossby wave propagation in a barotropic atmosphere

Dynamics of Atmospheres and Oceans ◽

10.1016/0377-0265(83)90013-1 ◽

1983 ◽

Vol 7 (2) ◽

pp. 111-125 ◽

Cited By ~ 89

Author(s):

David J. Karoly

Keyword(s):

Wave Propagation ◽

Rossby Wave ◽

Barotropic Atmosphere ◽

Rossby Wave Propagation

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Intraseasonal to decadal variability of Rossby wave packet properties

10.5194/egusphere-egu21-8828 ◽

2021 ◽

Author(s):

Georgios Fragkoulidis ◽

Volkmar Wirth

Keyword(s):

Rossby Wave ◽

Large Scale ◽

Decadal Variability ◽

Phase Speed ◽

Diagnostic Methods ◽

Temperature And Precipitation ◽

Ongoing Work ◽

Large Scale Flow

<p>The large-scale extratropical upper-tropospheric flow tends to organize itself into eastward-propagating Rossby wave packets (RWPs). Investigating the spatiotemporal evolution of RWPs and the underlying physical processes has been beneficial in showcasing the role of the upper-tropospheric flow in temperature and precipitation extremes. The use of recently developed diagnostics of local in space and time wave properties has provided further insight in this regard. Motivated by the above, these diagnostic methods are now being employed to investigate the intraseasonal to decadal variability of key RWP properties such as their amplitude, phase speed, and group velocity in reanalysis datasets. It is shown that these properties exhibit a distinct seasonal and interregional variability, while interesting patterns thereof emerge. Moreover, the interannual and long-term variability in these RWP properties is explored and significant decadal trends for specific regions and seasons are highlighted. Ongoing work aims at further utilizing the presented diagnostics and analyses toward an improved understanding of the extratropical large-scale flow variability from weather to climate time scales.</p>

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Rossby Wave Propagation from the Arctic into the Midlatitudes: Does It Arise from In Situ Latent Heating or a Trans-Arctic Wave Train?

Journal of Climate ◽

10.1175/jcli-d-18-0780.1 ◽

2020 ◽

Vol 33 (9) ◽

pp. 3619-3633 ◽

Cited By ~ 2

Author(s):

Tingting Gong ◽

Steven B. Feldstein ◽

Sukyoung Lee

Keyword(s):

Wave Propagation ◽

Rossby Wave ◽

Wave Train ◽

The Arctic ◽

Latent Heating ◽

Latent Heat Release ◽

Rossby Wave Propagation ◽

Rossby Wave Train ◽

In Situ Generation

AbstractThe relationship between latent heating over the Greenland, Barents, and Kara Seas (GBKS hereafter) and Rossby wave propagation between the Arctic and midlatitudes is investigated using global reanalysis data. Latent heating is the focus because it is the most likely source of Rossby wave activity over the Arctic Ocean. Given that the Rossby wave time scale is on the order of several days, the analysis is carried out using a daily latent heating index that resembles the interdecadal latent heating trend during the winter season. The results from regression calculations find a trans-Arctic Rossby wave train that propagates from the subtropics, through the midlatitudes, into the Arctic, and then back into midlatitudes over a period of about 10 days. Upon entering the GBKS, this wave train transports moisture into the region, resulting in anomalous latent heat release. At high latitudes, the overlapping of a negative latent heating anomaly with an anomalous high is consistent with anomalous latent heat release fueling the Rossby wave train before it propagates back into the midlatitudes. This implies that the Rossby wave propagation from the Arctic into the midlatitudes arises from trans-Arctic wave propagation rather than from in situ generation. The method used indicates the variance of the trans-Arctic wave train, but not in situ generation, and implies that the variance of the former is greater than that of latter. Furthermore, GBKS sea ice concentration regression against the latent heating index shows the largest negative value six days afterward, indicating that sea ice loss contributes little to the latent heating.

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Rossby Wave Ray Tracing in a Barotropic Divergent Atmosphere

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2537.1 ◽

2008 ◽

Vol 65 (5) ◽

pp. 1679-1691 ◽

Cited By ~ 3

Author(s):

Chungu Lu ◽

John P. Boyd

Keyword(s):

Wave Propagation ◽

Ray Tracing ◽

Rossby Wave ◽

Level Structure ◽

Low Frequency ◽

Present Theory ◽

Wave Ray ◽

Divergent Wind ◽

Rossby Wave Propagation ◽

Upper Level

Abstract The effects of divergence on low-frequency Rossby wave propagation are examined by using the two-dimensional Wentzel–Kramers–Brillouin (WKB) method and ray tracing in the framework of a linear barotropic dynamic system. The WKB analysis shows that the divergent wind decreases Rossby wave frequency (for wave propagation northward in the Northern Hemisphere). Ray tracing shows that the divergent wind increases the zonal group velocity and thus accelerates the zonal propagation of Rossby waves. It also appears that divergence tends to feed energy into relatively high wavenumber waves, so that these waves can propagate farther downstream. The present theory also provides an estimate of a phase angle between the vorticity and divergence centers. In a fully developed Rossby wave, vorticity and divergence display a π/2 phase difference, which is consistent with the observed upper-level structure of a mature extratropical cyclone. It is shown that these theoretical results compare well with observations.

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