The summertime 12-h wind oscillation with zonal wavenumber &amp;lt;i&amp;gt;s&amp;lt;/i&amp;gt; = 1 in the lower thermosphere over the South Pole

Portnyagin, Yu. I.; Forbes, Jeffrey M.; Makarov, N. M.; Merzlyakov, E. G.; Palo, S. E.

doi:10.1007/s00585-998-0828-9

Cited by 71 publications

(118 citation statements)

References 24 publications

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“…Early results from our observations over the South Pole have con®rmed the existence of a 12 h oscillation Portnyagin et al, 1997b) which was ®rst observed by Collins et al (1992) in sodium densitȳ uctuations and then by Hernandez et al (1993) in the meridional wind ®eld. Additionally, a strong divergence event in April 1996 was observed and presented in Portnyagin et al (1997a).…”

Section: Introductionsupporting

confidence: 51%

“…2 is a strong 12 h (2 cycles/day) oscillation during the summer months from October through February which wanes during the winter months (Portnyagin et al, 1997b). Also present is a strong 24 h oscillation with the same type of seasonal behavior as the 12 h oscillation.…”

Section: Wave Spectramentioning

confidence: 93%

“…A spectrum which is independent of zonal wave number was presented in Portnyagin et al (1997b). This spectrogram was computed for each of the four azimuthal directions and then these four spectrograms were averaged to produce a single spectrogram which describes the average wave activity over the South Pole.…”

Section: Wave Spectramentioning

confidence: 99%

“…There is a clear seasonal dependence with eastward propagating waves being observed primarily during winter and strong 12 and 24 h westward propagating oscillations observed during the summer Forbes et al, 1995;Portnyagin et al, 1997b). In this study we will focus on the eastward propagating longperiod waves which have been observed using the meteor radar over the South Pole.…”

Section: Introductionmentioning

confidence: 99%

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Transient eastward-propagating long-period waves observed over the South Pole

et al. 1998

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Abstract. Observations of the horizontal wind ®eld over the South Pole were made during 1995 using a meteor radar. These data have revealed the presence of a rich spectrum of waves over the South Pole with a distinct annual occurrence. Included in this spectrum are longperiod waves, whose periods are greater than one solar day, which are propagating eastward. These waves exhibit a distinct seasonal occurrence where the envelope of wave periods decreases from a period of 10 days near the fall equinox to a minimum of 2 days near the winter solstice and then progresses towards a period near 10 days at the spring equinox. Computation of the meridional gradient of quasi-geostrophic potential vorticity has revealed a region in the high-latitude upper mesosphere which could support an instability and serve as a source for these waves. Estimation of the wave periods which would be generated from an instability in this region closely resembles the observed seasonal variation in wave periods over the South Pole. These results are consistent with the hypothesis that the observed eastward propagating long-period waves over the South Pole are generated by an instability in the polar upper mesosphere. However, given our limited data set we cannot rule out a stratospheric source. Embedded in this spectrum of eastward propagating waves during the austral winter are a number of distinct wave events. Eight such wave events have been identi®ed and localized using a constant-®lter bank. The periods of these wave events ranges from 1.7 to 9.8 days and all exist for at least 3 wave periods. Least squares analysis has revealed that a number of these events are inconsistent with a wave propagating zonally around the geographic pole and could be related to waves propagating around a dynamical pole which is o set from the geographic pole. Additionally, one event which was observed appears to be a standing oscillation.

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Section: Introductionsupporting

confidence: 51%

Section: Wave Spectramentioning

confidence: 93%

Section: Wave Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transient eastward-propagating long-period waves observed over the South Pole

et al. 1998

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“…The installation of a meteor radar at the South Pole and its successful operation without interruption during two observational campaigns; January 19, 1995±Janu-ary 26, 1996, and November 21, 1996±January 27, 1997, provided unique opportunities for investigation of a broad spectrum of waves in the wind ®eld in the lower thermosphere over the South Pole for di erent seasons (Forbes et al, 1995;Portnyagin et al, 1996;Portnyagin et al, 1997Portnyagin et al, , 1998Palo et al, 1998). In these papers the main features in the seasonal behavior of the di erent wind oscillations at an average height of 95 km over the South Pole with characteristic periods equal to or greater than 12 h are discussed in detail.…”

Section: Introductionmentioning

confidence: 99%

Intradiurnal wind variations observed in the lower thermosphere over the South Pole

et al. 2000

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Abstract. The ®rst meteor radar measurements of meridional winds in the lower thermosphere (about 95 5 km), along four azimuth directions: 0°, 90°E, 180°and 90°W; approximately 2°from the geographic South Pole were made during two observational campaigns: January 19, 1995±January 26, 1996, and November 21, 1996±January 27, 1997. Herein we report analyses of the measurement results, obtained during the ®rst campaign, which cover the whole one-year period, with particular emphasis on the transient nature and seasonal behavior of the main parameters of the intradiurnal wind oscillations. To analyze the data, two complementary methods are used: the well-known periodogram (FFT) technique and the S-transform technique. The most characteristic periods of the intradiurnal oscillations are found to be rather uniformly spread between about 7 h and 12 h. All of these oscillations are westward-propagating with zonal wave number s 1 and their usual duration is con®ned to several periods. During the austral winter season the oscillations with periods less than 12 h are the most intensive, while during summer season the 12-h oscillations dominate. Lamb waves and internal-gravity wave propagation, non-linear interaction of the short-period tides, excitation in situ of the short period waves may be considered as possible processes which are responsible for intradiurnal wind oscillations in the lower thermosphere over South Pole.

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Winter temperature tides from 30 to 110 km at McMurdo (77.8°S, 166.7°E), Antarctica: Lidar observations and comparisons with WAM

Fong

Chu

et al. 2014

J. Geophys. Res. Atmos.

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We provide the first characterization of diurnal and semidiurnal thermal tides in temperature from 30 to 110 km in the winter season (May through August) at McMurdo (77.8°S, 166.7°E), Antarctica. The observations were made with an Fe Boltzmann temperature lidar in 2011 and 2012. Over 330 h of winter data are compiled into a composite day of temperature perturbations that significantly reduce the incoherent wave effects while preserving the coherent tidal signatures. Both diurnal and semidiurnal tides have small amplitudes (less than 3 K) below 100 km with vertical wavelengths of~29 and~23 km, respectively. A new finding of this study is the fast growth of diurnal and semidiurnal tidal amplitudes above 100 km to at least 15 K near 110 km, exceeding that of the freely propagating tides originating from the lower atmosphere. Such fast growth exists for all Kp index cases and diurnal amplitude increases to 15-30 K at 110 km with larger Kp indices corresponding to larger tidal amplitudes and faster growth rates. The slopes of diurnal tidal phases become steeper above 100 km, and the tidal phases barely change with altitude from 100 to 106 km. The tidal growth behavior is reproduced in the Whole Atmosphere Model (WAM) with phases comparable to the observations but magnitudes significantly underestimated. WAM compares reasonably well with the observations below 100 km. The observed significant amplitude increases and phase structure changes suggest additional tidal sources near or above 100 km, which deserve future investigation. IntroductionAtmospheric tides are global-scale oscillations in pressure, density, temperature, and wind fields for which the periods are harmonics of a solar day. They can be classified as migrating (Sun-synchronous) and nonmigrating (non-Sun-synchronous) tides according to their horizontal phase velocities, i.e., migrating tides follow the motion of the Sun. The driving forces of migrating tides are mainly periodic absorption of solar radiation in the atmosphere, and those for nonmigrating tides are mainly latent heat release in the tropical region [Hagan and Forbes, 2002;Zhang et al., 2010aZhang et al., , 2010b and nonlinear interactions between planetary waves and migrating tides [Angelats i Coll and Forbes, 2002;Hagan and Roble, 2001;Murphy et al., 2009]. Tides can obtain large amplitudes in the middle and upper atmosphere, where they modulate ionospheric variability via the E region dynamo effect [Forbes et al., 2000;Forbes et al., 2008], enhance vertical atmosphere coupling [Forbes et al., 2000;Immel et al., 2006], and cause instabilities by inducing significant temperature gradients and wind shears [Hecht et al., 1997;Liu et al., 2004]. Tides affect the propagation of gravity waves (GWs) [Walterscheid, 1981;Lu et al., 2009] and modulate GW momentum fluxes [Fritts and Vincent, 1987;Espy et al., 2004;Liu et al., 2013]. Tides also impact the vertical transport of atmospheric constituents and thereby the total solar heating in the upper part of the middle atmosphere [Smith et al., ...

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The summertime 12-h wind oscillation with zonal wavenumber <i>s</i> = 1 in the lower thermosphere over the South Pole

Abstract: Abstract. Meteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one s 1. The wind measurements are con®ned to the periods from

Cited by 71 publications

References 24 publications

Transient eastward-propagating long-period waves observed over the South Pole

Transient eastward-propagating long-period waves observed over the South Pole

Intradiurnal wind variations observed in the lower thermosphere over the South Pole

Winter temperature tides from 30 to 110 km at McMurdo (77.8°S, 166.7°E), Antarctica: Lidar observations and comparisons with WAM

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