Observations of the phase‐locked 2 day wave over the Australian sector using medium‐frequency radar and airglow data

Hecht, J. H.; Walterscheid, R. L.; Gelinas, L. J.; Vincent, R. A.; Woithe, J. M.

doi:10.1029/2009jd013772

Cited by 34 publications

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References 34 publications

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“…Figure 7b,c shows the amplitude and phase of the NS winds filtered with a bandpass between 40 and 60 h, with the phase referenced to an oscillation with a period of 48 h. In general, the increase of phase with time indicates a period less than 48 h, but the steady phase observed between about day 21 and 29 shows the period at this time was close to 48 h. The same behaviour was observed Walterscheid and Vincent (1996). Studies of radar and airglow emissions from the MLT by Hecht et al (2010) corroborated the phase-locking mechanism. They found the airglow intensity response was much larger than what would be expected from the airglow temperature response, suggesting that the QTDW is causing a significant composition change, possibly due to minor constituent transport.…”

Section: The Quasi-two-day Wave and Its Impact On The Mltsupporting

confidence: 51%

The dynamics of the mesosphere and lower thermosphere: a brief review

Vincent

2015

Prog. in Earth and Planet. Sci.

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The dynamics of the mesosphere-lower thermosphere (MLT) (60 to 110 km) is dominated by waves and their effects. The basic structure of the MLT is determined by momentum deposition by small-scale gravity waves, which drives a summer-to-winter pole circulation at the mesopause. Atmospheric tides are also an important component of the dynamics of the MLT. Observations from extended ground-based networks, satellites as well as numerical modelling show that non-migrating tidal modes in the MLT are more important than previously thought, with evidence for directly coupling into the thermosphere/ionosphere. Major disturbances lower in the atmosphere, such as wintertime sudden stratospheric warmings, temporarily disrupt the circulation pattern and thermal structure of the MLT. In the equatorial mesosphere, gravity wave driving leads to oscillations in the zonal wind on semiannual time scales, although variability on quasi-biennial time scales is also apparent. Planetary-scale waves such as the quasi-two-day wave temporarily dominate the dynamics of the summertime MLT, especially in the southern hemisphere. Impacts may include short-term changes to the thermal structure and physics of the high-latitude MLT. Here, we briefly review the dynamics of the MLT, with a particular emphasis on developments in the past decade.Keywords: Atmospheric tides; Gravity waves; Planetary waves; Middle atmosphere; Mesosphere; Lower thermosphere; Wave coupling Review IntroductionThe mesosphere-lower thermosphere (MLT) is defined as the region of the atmosphere between about 60 and 110 km in altitude. It constitutes the upper part of what is often referred to as the middle atmosphere (10 to 110 km). The MLT is dominated by the effects of atmospheric waves, including planetary waves, tides and gravity waves. The source regions for these waves are lower in the atmosphere. As the waves propagate upward their amplitudes grow exponentially to compensate for the decrease in atmospheric density (e.g. Andrews et al. 1987). Consequently, wave motions often dominate the wind field in the MLT, so considerable averaging may be required to extract the mean flow, especially that of the mean meridional (NS) motions, which are smaller than the zonal (EW) flow. Zonal-mean zonal winds are eastward (westward) in the winter (summer) middle atmosphere, reaching peak values of approximately 60 to 70 ms −1 near 70 km and Correspondence: robert.vincent@adelaide.edu.au Department of Physics, School of Physical Sciences, University of Adelaide, North Terrace., SA, 5005 Adelaide, Australia then they reduce in magnitude until they reverse sign at heights between 90 and 100 km.Large wave amplitudes lead to wave breaking and hence momentum deposition. This, in turn, produces body forces that drive large scale residual circulations. In the winter stratosphere (approximately 20 to 60 km), planetary wave breaking drives a residual circulation from the equator to the winter pole, while in the mesosphere, gravity wave breaking and dissipation drives a circulation from ...

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Section: The Quasi-two-day Wave and Its Impact On The Mltsupporting

confidence: 51%

The dynamics of the mesosphere and lower thermosphere: a brief review

Vincent

2015

Prog. in Earth and Planet. Sci.

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“…Several past observational and modeling studies have found strong evidence for various tidal/planetary wave interactions, including the generation of nonmigrating tides through interaction between the stationary planetary wave 1 (PW1) and the migrating diurnal tide [ Hagan and Roble , 2001; Lieberman et al , 2004; Liu et al , 2007], PW1 and the migrating semidiurnal tide [ Angelats i Coll and Forbes , 2002; Chang et al , 2009], as well as between the tides and various propagating planetary waves [ Walterscheid and Vincent , 1996; Pancheva et al , 2002; Palo et al , 2007; Hecht et al , 2010; McCormack et al , 2010]. Numerical experiments performed in these studies [ Hagan and Roble , 2001; Angelats i Coll and Forbes , 2002; Liu et al , 2007; Chang et al , 2009] have resolved wave and tidal components that could be generated only as a result of a nonlinear planetary wave/tidal interaction, while observations indicated child wave components and tidal amplitude fluctuations whose time variation closely followed that of the interacting planetary wave in the regions where the tide was dominant [ Pancheva et al , 2002; Lieberman et al , 2004; Palo et al , 2007; Chang et al , 2009; Hecht et al , 2010; McCormack et al , 2010].…”

Section: Introductionmentioning

confidence: 99%

Short-term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave

Chang¹,

Palo²,

Liu³

2011

J. Geophys. Res.

182

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[1] The migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the Earth's mesosphere and lower thermosphere (MLT) region, representing the atmospheric response to the largest component of solar forcing. Ground-based observations of the tide have resolved short-term variations attributed to nonlinear interactions between the tide and planetary waves that are also in the region. Using the NCAR Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM), we simulate a quasi 2 day wave (QTDW) event under late-January conditions. In this case, sideband sum and difference child waves are resolved, indicating that a nonlinear interaction is occurring between the QTDW and the tide. The migrating diurnal tide in the MLT displays local amplitude decreases of 20-40%, as well as a shortening of vertical wavelength by roughly 4 km. Examining the physical mechanisms driving the interaction, nonlinear advection is found to result in amplification of the tide in some regions and damping in others, manifesting as increased smoothing of the tidal structure when the QTDW is present in the MLT. Additionally, the QTDW also enhances the easterly summer mean wind jet that can also account for changes in tidal amplitude and vertical wavelength. We find that QTDW-induced background atmosphere changes in TIME-GCM can drive tidal variability at levels greater than nonlinear advection, a possibility not previously considered.Citation: Chang, L. C., S. E. Palo, and H.-L. Liu (2011), Short-term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave,

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“…The 2 day wave is important in the dynamics of the middle atmosphere because it is known to strongly interact with atmospheric tides and to modulate their amplitude [e.g., Teitelbaum and Vial , 1991; Mitchell et al , 1996; Palo et al , 1999; Pancheva et al , 2004; Wu et al , 2008]. Further, there is evidence that the 2 day wave can become phase locked to the migrating semidiurnal and diurnal tides (i.e., have a period of exactly 48 h) and through interaction with them generate a diurnal zonal wave number 6 feature and lead to rapid amplification of the 2 day wave amplitude [e.g., Walterscheid and Vincent , 1996; Hecht et al , 2010; McCormack et al , 2010]. Interactions with tides can also act to constrain 2 day wave amplitudes and results in a cascade of variance to smaller scales within the atmosphere [ Salby and Callaghan , 2008].…”

Section: Introductionmentioning

confidence: 99%

Zonal wave numbers of the summertime 2 day planetary wave observed in the mesosphere by EOS Aura Microwave Limb Sounder

2011

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Recent observations and theoretical work suggest that the 2 day planetary wave in the summertime mesosphere is composed of multiple superposed zonal wave numbers. Here we use EOS Aura Microwave Limb Sounder (MLS) temperature data to determine the component zonal wave numbers of the 2 day wave in the mesosphere at latitudes of 70°S to 70°N from 2004 to 2009. We consider the effect of aliasing between different wave numbers and note that significant aliasing can occur and result in spurious signals, particularly at high latitudes in winter. The seasonal evolution of the different wave numbers is investigated and found to be very different between the Northern and Southern Hemispheres. In both hemispheres the wave is dominated by westward traveling waves of zonal wave number 3 and 4 (W3 and W4). However, in the Southern Hemisphere the wave is dominated by the W3 component, but in the Northern Hemisphere the W3 component is smaller and the W4 component is often of similar or larger amplitude. A small‐amplitude westward traveling zonal wave number 2 (W2) wave is also evident in both hemispheres. In the Northern Hemisphere, the W2 amplitudes never exceed 3 K, the W3 amplitudes can reach 3.5 K, and the W4 can be the largest component, reaching amplitudes of 4 K. In the Southern Hemisphere, the W2 amplitudes can reach up to 3.5 K, the W3 amplitudes can be much larger, reaching 12 K, and the W4 amplitudes are smaller than in the Northern Hemisphere, in 4 out of 5 years not exceeding 3 K. The Northern Hemisphere W4 can reach large amplitudes in August when the W3 is small, which means that the late summer Northern Hemisphere quasi‐2 day wave is usually a W4 oscillation rather than the familiar W3. In contrast, in the Southern Hemisphere, the W3 is often larger than the W4 around the summer solstice, and there are no episodes observed where the wave becomes dominated by the W4 for an extended period of time. A high degree of interannual variability is evident, particularly in the Southern Hemisphere, where the W3 peak amplitudes vary from 12 K in January 2006 to 3 K in January 2009. The height‐latitude structure of the W4 suggests that this wave is a (4, 0) Rossby‐gravity wave.

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Observations of the phase‐locked 2 day wave over the Australian sector using medium‐frequency radar and airglow data

Cited by 34 publications

References 34 publications

The dynamics of the mesosphere and lower thermosphere: a brief review

The dynamics of the mesosphere and lower thermosphere: a brief review

Short-term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave

Zonal wave numbers of the summertime 2 day planetary wave observed in the mesosphere by EOS Aura Microwave Limb Sounder

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