Planetary Waves in the Upper Stratosphere in Early 1966

Hirota, Isamu

doi:10.2151/jmsj1965.46.5_418

Cited by 26 publications

(7 citation statements)

References 18 publications

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“…One of the well-known characteristics of a sudden warming event is the downward propagation of a warm layer from about 45 km into the lower stratosphere as seen by singlestation rocket measurements and satellite radiance data [Scott, 1972;Quiroz, 1969Quiroz, , 1971. It is generally assumed that this downward propagating warm layer is attributed to changes in zonally averaged thermal structure [Matsuno, 1971], but recent evidence indicates that the warming may be highly nonzonal, as was first suggested by Hirota [1968]. Figure 4a ing, but this increase may have been overestimated by previous authors because of the presence of thermal waves.…”

Section: Vertical Structure Of the Sudden Warmingmentioning

confidence: 92%

Stratospheric warmings: Observations and theory

Schoeberl¹

1978

Reviews of Geophysics

218

125

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Winter stratospheric warming observations and associated theories are reviewed. Historically, major warmings occur on the average every other year and may thus be considered an important climatological component of the winter stratosphere. The warming results from eddy heat transport from equatorial latitudes into the polar regions. The eddies chiefly responsible for the transport are the planetary scale waves which may attain amplitudes twice their monthly average values in the lower stratosphere prior to the warming. In the troposphere this amplitude increase is associated with the development of blocking patterns. The warming is shown to have a strong nonzonal component in the upper stratosphere, a feature not fully recognized by modelers. The critical level theory of the sudden stratospheric warming provides a simple dynamic explanation of the event. Yet mechanistic numerical models which have reproduced many features of the warming exhibit results which tend to indicate that the interaction of planetary waves and the mean flow occurs through a variety of mechanisms including transience and damping. The close connection between blocking in the troposphere and the development of the sudden warming is likely to be a result of resonance of free planetary waves in a stratospheric wind cavity.

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Section: Vertical Structure Of the Sudden Warmingmentioning

confidence: 92%

Stratospheric warmings: Observations and theory

Schoeberl¹

1978

Reviews of Geophysics

218

125

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“…We thus have a preliminary alternate explanation for the bi-weekly oscillation of stratospheric zonal winds and planetary wave amplitudes observed by Hirota (1968). Hirota (1971) invokes a periodic forcing of the stratosphere to excite the oscillation; but this study suggests that it may result naturally from second-order interactions between traveling and forced stationary modes in situ -no external time dependent forcing being needed.…”

Section: A Stationary Component Which Oscillates Inmentioning

confidence: 81%

“…Hirota (1971) invokes a periodic forcing of the stratosphere to excite the oscillation; but this study suggests that it may result naturally from second-order interactions between traveling and forced stationary modes in situ -no external time dependent forcing being needed.…”

Section: A Stationary Component Which Oscillates Inmentioning

confidence: 84%

Atmospheric Response to the Quasi-Resonant Growth of Forced Planetary Waves

Clark

1974

Journal of the Meteorological Society of Japan

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The forcing of the second-order zonally-averaged wind and temperature fields due to the quasiresonant growth of planetary waves in a two-layer model is considered.Dissipation in the form of linear drag and Newtonian cooling is allowed for. Calculations are made in a mid-latitude * -plane channel bounded by two vertical walls . The linear or first order solution is constrained so as to not transport momentum meridionally.Three neutral modes in the adiabatic two layer model are brought to resonance separately by adjusting the basic zonal flow configuration.For a dissipation time scale of 2 days, the quasi-resonant enhancement of the response is negligible. A time scale of 4 days is used.For resonance involving the two layer equivalent of the Rossby wave, the strong westerly zonal flow configuration causes most of the second order effects to be confined to the lowest few scale heights, where a slow easterly acceleration of the zonal flow occurs.A second resonance associated with weak westerlies surmounted by moderate westerlies leads to a very rapid high level easterly acceleration lasting about two weeks. A final resonant wind configuration with easterlies above westerlies is associated with very rapid temperature rises near the pole.Calculations suggest that the quasi-resonant enhancement of the planetary wave-zone flow interaction resulting from certain basic flow configurations might be the explanation of the stratospheric warming.It is hypothesized that the timing of warmings is determined by how well tuned the zonal flow structure is in the sense that appreciable secondorder effects will result in response to small influxes of planetary-wave energy from below. Furthermore, it is suggested that the subsequent evolution of a warming into a full scale warming depends on the ability of the zonal flow configuration to evolve through a series of tuned or resonant states.

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“…The temperature and geopotential fields show pronounced structure in longitude associated with wave numbers 1 and 2 so that observations at a single ground station do not provide a realistic picture of the longitudinal mean behavior of the perturbed atmosphere. The availability of global scale satellite measurements [Barnett et al, 1975;Houghton, 1978] and theoretical studies [Hirota, 1968;Schoeberl and Strobel, 1980] have led to an increased appreciation of the nonzonal nature of the warmings. Observations of total ozone during warmings reveal significant variations owing to horizontal transport in the lower stratosphere [Deutsch, 1962;London, 1963].…”

Section: Introductionmentioning

confidence: 99%

“…The initial temperature at 60 km was unusually high, and this distorts the appearance of a continuous descent of the warm region. When observed from a single station this apparent downward propagation of warm air results from the westward motion of a planetary scale temperature wave whose phase varies with altitude [Hirota, 1968;Schoeberl, 1978]. The lower panel of Figure 1 depicts the variations in atmospheric bulk density computed from the observed temperature assuming hydrostatic balance.…”

Section: Introductionmentioning

confidence: 99%

Photochemical processes induced by a major warming of the upper atmosphere: Variations in mesospheric trace constituents

Frederick

1981

J. Geophys. Res.

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The temperature rise and enhanced winds during an upper atmospheric warming cause substantial changes in the high level ozone profile of the sunlit winter hemisphere. Calculations based on a photochemical model, using temperatures measured at Fort Churchill during a major warming, predict a factor of 2 variation in the ozone number density near 60 km over a time period of approximately 3 weeks. This temporal variability at a fixed location results from the planetary wave structure of the temperature field and reflects a similar longitudinal behavior at a given time. The ozone number density at fixed altitude is a maximum when the temperature is greatest at and below this level. This is due primarily to thermal expansion of the atmosphere which results in a large increase in pressure at constant altitude. However, chemical activity during a warming decreases the mesospheric ozone mixing ratio at fixed pressure. The ozone mixing ratio at constant pressure during the peak of the event studied is near 75% of its unperturbed value. The predicted variability of ozone in longitude and time demonstrates the need for hemispheric scale information on trace gas abundances, temperature, and winds in order to delineate adequately the response of upper atmospheric composition to a major perturbation.

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Planetary Waves in the Upper Stratosphere in Early 1966

Cited by 26 publications

References 18 publications

Stratospheric warmings: Observations and theory

Stratospheric warmings: Observations and theory

Atmospheric Response to the Quasi-Resonant Growth of Forced Planetary Waves

Photochemical processes induced by a major warming of the upper atmosphere: Variations in mesospheric trace constituents

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