Rossby wave

An analysis of the recent observation data [30,31] shows that baroclinic Rossby waves that are generated off the eastern coasts in the northern parts of the Pacific and Atlantic oceans in a period of about a year represent their dominant non-stationary dynamical response to the annual cycle of the atmospheric forcing in the latitudinal range from 10-15° to 45-50°N. In so doing, their mean phase velocities (0.02-0.03 ms 1 at 40-45°N) are higher than the theoretical values (about 0.01 ms-1). A similar situation is observed in the Black Sea as well [27]. In [32], several reasons of this phenomenon were listed such as the interaction with more large-scale non-stationary processes, topographic and nonlinear effects, and insufficient duration and spatiotemporal resolution of the observation data. 

The authors of [50] regarded the eddies as manifestations of Rossby waves modified by the bottom topography. The parameters of similar waves obtained from the data of altimeter observations (see Sect. 2.4), except for the period, are close to the model values. The annual wave period, which prevails in the observations, is absent in the model this is related to the forcing of the model BSGC by a constant mean annual wind field. 

One can find one more manifestation of the intra-annual evolution of the fields shown in Fig. 8 in the displacement and changes in the intensities of the local salinity extremes—the central maximums and the near-shore min-imums. The most distinct change is the westward displacement of the central salinity maximums occurring from February to May (see Fig. 8a,b) with the formation of a common maximum centered at 32° E in August (see Fig. 8c). The August salinity field at the 100-m level is characterized by an alternation of minimums and maximums from the east to the west with a wavelength of 350-400 km, well known as Knipovich s spectacles [2-4], With respect to their sizes, directions, and phase shift rates, they correspond to mid-latitude baroclinic Rossby waves [22,23]. 

Model studies of the medium-scale wave dynamics of the Black Sea waters [23] showed the possibility of the existence of Rossby waves with a period of about half a year, a wavelength of 250 km, and a phase velocity of 2 km day-1 in this sea. The model Rossby waves were generated by the wind... 

CipoUini, P., Cromwell, D., Challenor, P., and Raffaglio, S. (2001). Rossby waves detected in global ocean colour data. Geophys. Res. Lett. 28, 323—326. 

Li H., Colgate S. A., Wendroff B., and Liska R. (2001) Rossby wave instability of thin accretion disks III. Nonlinear simulations. Astrophys J. 551, 874-896. 

Standing planetary Rossby waves (Lau and Waliser, 2005). Their meridional troughs and... 

Figure 3.29. Fine-scale structure of a tracer in the vicinity of the polar vortex from 6 January to 16 January 1992 on the 850 K isentropic surface. The calculation made with NMC-analyzed winds show that, as a result of Rossby wave breaking, air is ejected from the polar vortex as long filamentary structures. This process transfers vortex air into mid-latitudes. From Waugh et al.( 1994).

Figure 3.34 Eliassen-Palm (EP) flux (arrows) and its divergence (dashed lines) represented as a function of altitude and latitude for January. The EP flux propagates in the stratosphere only during winter. The EP flux divergence is associated with Rossby wave transience and dissipation. Courtesy of W. Randel, NCAR (2001).

From spring to faU, the intrusion water from the Pacific is narrowly confined to the continental slope south of China, only in winter, when the northeast monsoon becomes fully developed, can it spread in the southern South China Sea. The seasonal cycle over most of the SCS basin is determined predominantly by the regional dynamics within the SCS, and is forced mainly by smface wind stress curl on baroclinic Rossby waves. Furthermore, the Kmoshio also exerts a significant influence on the SCS. However, the water exchange in the Luzon Strait is very complex. 

In summer the vorticity center over the NSCS weakens, whereas wind stresses over the SSCS reverse to an anticyclone. Another reasonable interpretation is that the propagation of the Rossby wave in the SSCS is much faster than that the NSCS. As a result, the SSCS can respond to the external forcing more quickly than the NSCS (Yang, 2000). 

Platzman, G.W. (1968). The Rossby wave. Quart. Journal Meteorological Society 94 225-248. Platzman, G.W. (1970). Ocean tides and related waves. Lectures in Applied Math. 14 239-291. Platzman, G.W. (1972). Two-dimensional free oscillations in natural hasias. Journal of Physical Oceanography 2 2) 117-138. 

Planetary wave A very large-scale Rossby wave (horizontal wavelength of 10,000-40,000 km). Planetary waves are the dominant type ofwave in the extratropical stratosphere dining winter. 

Rossby wave A westward-propagating wave that originates from the variation of the Coriohs parameter with latitude. 

The disturbances in the stratospheric circulation seen in Fig. 7b are caused by atmospheric waves that propagate upward from the troposphere. The dominant type of wave in the extratropical stratosphere is the Rossby wave (see Section IV.B.2). Rossby waves found in the stratosphere are of very large scale, having horizontal wavelengths of tens of thousands of kilometers for these reason, these Rossby waves are often referred to as planetary waves. ... 

The planetary Rossby waves responsible for the distortion of the zonal jets in winter, and for the sudden warming phenomenon, are quasistationary that is, these waves move only slightly with respect to the Earth s surface. The marked differences between the wintertime circulation of the Northern and Southern hemispheres is due to the weaker amplitude of quasistationary planetary waves in the latter, as illustrated in Fig. 9. This, in turn, is probably related to the concentration of continental land masses in the Northern Hemisphere. Major orographic features are known to excite planetary waves when the tropospheric jet streams blow strongly across them, as is the case during winter the thermal contrast between continents and oceans is also known to excite planetary waves. 

The gravity waves just described occur at high frequencies and small scales. For motions with intrinsic periods greater than a day, and horizontal scales of the order of 1000 km or larger, a distinct type of wave motion appears, the Rossby wave (named after Carl Gustav Rossby, who first pointed out their meteorological importance in the 1930s). The Rossby wave owes its existence to the variation of the Coriolis parameter, /, with latitude. 

A governing equation for Rossby waves can be derived by noting, first of all, that at low frequencies and ontside the tropics, the eddy momentum equations (24) and (25) reduce to the condition of geostrophic equilibrinm ... 

Substitution into (37) of a solution of the form (31) leads immediately to the dispersion relation for Rossby waves,... 

This simple condition can be used to explain both the the seasonal behavior and the horizontal scale of Rossby waves formd in the stratosphere. The first inequality on (41) implies that quasi-stationary (c —y 0) waves will not be found in the summer stratosphere. This prediction is borne out by observations, as shown inFig. 9. In the stratosphere, where i/ < 0 in smnmer, quasistationary waves are absent in fact, the summertime stratospheric circulation essentially follows latitude circles, as seen earlier in connection with Fig. 7. 

The second inequality determines the scale of the waves that can propagate vertically in winter, when the zonal-mean zonal wind is eastward (u >0). For example, the midlatitude troposphere is dominated by slow westward-moving Rossby waves with horizontal scales on the order of a few thousand kilometers that arise from instability of the tropospheric flow. However, these waves are not found in the stratosphere because their horizontal wavenumbers k = l7t/kx) are relatively large so the second inequality cannot be satisfied for typical values of u. On the other hand, very large scale waves (horizontal wavelengths of tens of thousands of kilometers) have smaller horizontal wavenumbers and can propagate into the stratosphere. This accounts for the fact that the wave field in the winter stratosphere is dominated by planetary-scale Rossby waves, with wavenumber k in the range 1-3. 

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