Eliassen-Palm Flux Diagnostics and the Effect of the Mean Wind on Planetary Wave Propagation for an Observed Sudden Stratospheric Warming

Kanzawa, Hiroshi

doi:10.2151/jmsj1965.60.5_1063

Cited by 21 publications

(11 citation statements)

References 25 publications

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“…Our results reveal that while the 2009 prewarming period was characterized by vertically propagating waves, the split SSW itself was characterized by the signature of resonance. This result is in qualitative agreement with previous observational studies that showed that split-SSW prewarming periods are characterized by planetary waves with significant westward tilt, while the warmings themselves are characterized by wave events with little to no vertical phase tilt (Kanzawa 1980(Kanzawa , 1982Naujokat et al 2002).…”

Section: Introductionsupporting

confidence: 92%

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

Albers

Birner

2014

Journal of the Atmospheric Sciences

154

180

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Reanalysis data are used to evaluate the evolution of polar vortex geometry, planetary wave drag, and gravity wave drag prior to split versus displacement sudden stratospheric warmings (SSWs). A composite analysis that extends upward to the lower mesosphere reveals that split SSWs are characterized by a transition from a wide, funnel-shaped vortex that is anomalously strong to a vortex that is constrained about the pole and has little vertical tilt. In contrast, displacement SSWs are characterized by a wide, funnel-shaped vortex that is anomalously weak throughout the prewarming period. Moreover, during split SSWs, gravity wave drag is enhanced in the polar night jet, while planetary wave drag is enhanced within the extratropical surf zone. During displacement SSWs, gravity wave drag is anomalously weak throughout the extratropical stratosphere.Using the composite analysis as a guide, a case study of the 2009 SSW is conducted in order to evaluate the roles of planetary and gravity waves for preconditioning the polar vortex in terms of two SSW-triggering scenarios: anomalous planetary wave forcing from the troposphere and resonance due to either internal or external Rossby waves. The results support the view that split SSWs are caused by resonance rather than anomalously large wave forcing. Given these findings, it is suggested that vortex preconditioning, which is traditionally defined in terms of vortex geometries that increase poleward wave focusing, may be better described by wave events (planetary and/or gravity) that ''tune'' the geometry of the vortex toward its resonant excitation points.

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Section: Introductionsupporting

confidence: 92%

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

Albers

Birner

2014

Journal of the Atmospheric Sciences

154

180

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“…Following Palmer (1981Palmer ( , 1982 and Kanzawa (1982), the TEM formulation are expressed by, where (see Appendix A for undefined terms).…”

Section: Formulationmentioning

confidence: 99%

“…This definition of EP flux is simple even though the dimension is not correctly written. If this EP flux divided by RTs it is EP flux for unit volume (Kanzawa, 1982), and if by ps it is EP flux for unit mass (Palmer, 1982).…”

Section: Formulationmentioning

confidence: 99%

A Transformed Eulerian Mean Diagnostics for a Sun-Weather Relation

Misumi

1986

Journal of the Meteorological Society of Japan

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The aim of this study is to find a linkage of atmospheric responses to the solar sector boundary (SSB) passages (Wilcox et al., 1974;Misumi, 1981;1983). Variations of both zonal mean fields and planetary waves around the SSB passages are investigated using the transformed Eulerian mean (TEM) equations system including the refractive index. Deviations from the time mean field in 8 winters from 1964 to 1972 are mainly discussed.It is found that the Eliassen-Palm (EP) flux for zonal wavenumber 2 and 3 in the troposphere begins to decrease about 5 days prior to SSB passages. Such decrease leads to the divergence of the EP flux near the tropopause in high latitudes. This is responsible for the temperature decrease in the polar troposphere, and consequently for the decrease of the vorticity area index in the upper troposphere.The decreases of the EP flux for both wavenumber 2 originating from the troposphere and wavenumber 1 being at the 150mb level on 4 days before the SSB passages seem to create the minimum of the polar temperature in the middle stratosphere.Among above mentioned processes, only the decrease of the EP flux is not diagnosed by the TEM equations system.The decrease of the EP flux in the troposphere is statistically significant and is seen only in the same period that other atmospheric responses occur. This type response would be due to the external modulation.

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“…On the other hand, Palmer (1981a, b), O'Neill and Youngblut (1982) and Kanzawa (1982) analyzed the satellite data and showed that just before the sudden warming, the distribution of mean zonal winds has larger refractive index in the high latitudinal region than as usual, and that planetary waves which propagate southward in ordinary situation are directed northward. Such an extraordinary configuration of the mean zonal winds could be helpful to the growth of planetary wave.…”

Section: Introductionmentioning

confidence: 99%

Stratospheric Multiple Equilibria and Seasonal Variations

Wakata

Uryu

1987

Journal of the Meteorological Society of Japan

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Using a vertical one-dimensional model, we discuss the equilibrium of the stratospheric mean zonal flow and planetary wave forced by the surface corrugation.Their stabilities are also examined. It is shown that in late autumn and early spring, there exist two stable equilibrium solutions and one unstable equilibrium solution, while one stable equilibrium solution in mid-winter. It is noted that we have no vacillating solution as obtained by Holton and Mass (1976) and Chao (1985).Solving the time-dependent problems with changing the vertical shear of the basic zonal wind with one year period as an indicator of seasonal variation, we can obtain the growth of planetary wave twice in winter and the intensification of westerly wind between these two amplitude peaks. In addition, it is shown that a drastic transition of the mean zonal winds from westerlies to easterlies resembling the final warming occurs in later winter or early spring. These are very similar to the results of data analysis by Smith (1983) and those of the numerical simulation by Holton and Wehrbein (1980). Thus, the stratospheric seasonal variation can be interpreted as a hysteresis phenomenon caused by the change in the solar differential heating in the presence of multiple equilibria. The breakdown of polar, night vortex with the final warming is a kind of nonlinear instability. That is, if the winter westerly wind in the upper stratosphere is close to the Charney-Drazin's critical velocity and if it is perturbed by a planetary wave, then the refractive index is changed and this change causes the amplification of the wave. The amplified wave, in turn, changes the refractive index is changed and this change causes the amplification of the wave. The amplified wave, in turn, changes the refractive index by accelerating easterlies. This process provides a feedback, and the polar night vortex breaks down in the end. The present instability is not the resonance breakdown as in Plumb (1981).Finally, we make some comments on Chao's (1985) results.

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Eliassen-Palm Flux Diagnostics and the Effect of the Mean Wind on Planetary Wave Propagation for an Observed Sudden Stratospheric Warming

Cited by 21 publications

References 25 publications

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

Vortex Preconditioning due to Planetary and Gravity Waves prior to Sudden Stratospheric Warmings

A Transformed Eulerian Mean Diagnostics for a Sun-Weather Relation

Stratospheric Multiple Equilibria and Seasonal Variations

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