Waves with period near 3 days in the equatorial mesosphere and lower thermosphere over Ascension Island

Younger, P. T.; Mitchell, N. J.

doi:10.1016/j.jastp.2005.05.008

Cited by 19 publications

(14 citation statements)

References 18 publications

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“…The values are 44 ± 4 km for March, 62 ± 7 km for August and 45 ± 5 km for October-November. The vertical wavelengths inferred from wind measurements associated with UFKW in the MLT range from 35 to 85 km, and typical values are around 40 km (Vincent, 1993;Younger and Mitchell, 2006;Davis et al, 2012). Then our results reinforce that the three common 3-4-day oscillations observed in the airglow and wind are consistent with an UFKW interpretation.…”

Section: Wind and Airglow Spectral Analysissupporting

confidence: 86%

“…Just at the end of the airglow observations, the 3-4-day amplitudes increase in the zonal wind. Younger and Mitchell (2006) investigated the wind-field variability in the equatorial MLT at Ascension Island (8 • S, 14 • W) and observed relatively high activity of the 3-4-day wave in the meridional wind. They explained the presence of the 3-4-day waves in the meridional wind due to the presence of mixed Rossby-gravity waves and longperiod inertia-gravity waves.…”

Section: Wind and Airglow Spectral Analysismentioning

confidence: 99%

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Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides

et al. 2018

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Abstract. Airglow and wind measurements from the Brazilian equatorial region were used to investigate the presence and the effects of the 3-4-day ultrafast Kelvin waves in the MLT. The airglow integrated intensities of the OI557.7 nm, O 2 b(0-1) and OH(6-2) emissions, as well as the OH rotational temperature, were measured by a multichannel photometer, and the zonal and meridional wind components between 80 and 100 km were obtained from a meteor radar. Both instruments are installed in the Brazilian equatorial region at São João do Cariri (7.4 • S, 36.5 • W). Data from 2005 were used in this study. The 3-4-day oscillations appear intermittently throughout the year in the airglow. They were identified in January, March, July, August and October-November observations. The amplitudes induced by the waves in the airglow range from 26 to 40 % in the OI557.7 nm, 17 to 43 % in the O 2 b(0-1) and 15 to 20 % in the OH(6-2) emissions. In the OH rotational temperature, the amplitudes were from 4 to 6 K. Common 3-4-day oscillations between airglow and neutral wind compatible with ultrafast Kelvin waves were observed in March, August and October-November. In these cases, the amplitudes in the zonal wind were found to be between 22 and 28 m s −1 and the vertical wavelength ranges from 44 to 62 km. Evidence of the nonlinear interaction between the ultrafast Kelvin wave and diurnal tide was observed.

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Section: Wind and Airglow Spectral Analysissupporting

confidence: 86%

Section: Wind and Airglow Spectral Analysismentioning

confidence: 99%

Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides

et al. 2018

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“…Salby et al (1984) showed the presence of very fast Kelvin waves in the upper mesosphere. Numerous observations confirm that these waves are a frequent feature of the tropical MLT (e.g., Younger and Mitchell 2006;Takahashi et al 2007;Forbes et al 2009;Chang et al 2010). Kelvin waves with periods of 24 hours contribute to the observed spectrum of eastward propagating tidal motions.…”

Section: Planetary Wavesmentioning

confidence: 81%

Global Dynamics of the MLT

2012

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The transition between the middle atmosphere and the thermosphere is known as the MLT region (for mesosphere and lower thermosphere). This area has some characteristics that set it apart from other regions of the atmosphere. Most notably, it is the altitude region with the lowest overall temperature and has the unique characteristic that the temperature is much lower in summer than in winter. The summer-to-winter-temperature gradient is the result of adiabatic cooling and warming associated with a vigorous circulation driven primarily by gravity waves. Tides and planetary waves also contribute to the circulation and to the large dynamical variability in the MLT. The past decade has seen much progress in describing and understanding the dynamics of the MLT and the interactions of dynamics with chemistry and radiation. This review describes recent observations and numerical modeling as they relate to understanding the dynamical processes that control the MLT and its variability. Results from the Whole Atmosphere Community Climate Model (WACCM), which is a comprehensive high-top general circulation model with interactive chemistry, are used to illustrate the dynamical processes. Selected observations from the Sounding the Atmosphere with Broadband Emission Radiometry (SABER) instrument are shown for comparison. WACCM simulations of MLT dynamics have some differences with observations. These differences and other questions and discrepancies described in recent papers point to a number of ongoing uncertainties about the MLT dynamical system.

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“…Riggin et al (1997) also investigated by using ground based MF and meteor radars. Then several works regarding the UF-Kelvin wave characteristics observed from MF radars (Sridharan et al, 2002) and meteor radars (Younger and Mitchell, 2006) have also been reported. From the ground based airglow observation Takahashi et al (2002) reported 3-4 day period oscillation of the mesospheric airglow and OH temperature variations.…”

Section: Introductionmentioning

confidence: 99%

Possible influence of ultra-fast Kelvin wave on the equatorial ionosphere evening uplifting

et al. 2009

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Equatorial 3.5-day ultra-fast Kelvin wave was observed in the MLT zonal wind measured by meteor radar at Cariri (7.4• S, 36.5• W, geomag. 8• S) and in the stratosphere-mesosphere temperature structures from the TIMED/SABER data. The ionospheric F-layer bottom-side virtual height h F and the critical frequency f o F 2 observed at Fortaleza (3.9• S, 38.4• W, geomag. 5 • S) also showed similar oscillation structures, indicating an influence of the Kelvin wave in the F region height and modulation of E × B uplifting during the evening period. Consequently the ionospheric spread F onset time was also modulated in the same period, around 4 days.

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Waves with period near 3 days in the equatorial mesosphere and lower thermosphere over Ascension Island

Cited by 19 publications

References 18 publications

Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides

Ultrafast Kelvin waves in the MLT airglow and wind, and their interaction with the atmospheric tides

Global Dynamics of the MLT

Possible influence of ultra-fast Kelvin wave on the equatorial ionosphere evening uplifting

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