Large-amplitude semidiurnal temperature variations in the polar mesopause: evidence of a pseudotide

Walterscheid, R. L.; Sivjee, G. G.; Schubert, G.; Hamwey, Robert

doi:10.1038/324347a0

Cited by 72 publications

(36 citation statements)

References 13 publications

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“…The observations of these large terdiurnal tides are consistent with observations reported by Sivjee and Walterscheid (1994), Walterscheid et al (1986), Walterscheid and Sivjee (1996), and Walterscheid and Sivjee threshold values of 3 m/s for the diurnal tides and 2 m/s for the semidiurnal tides. The phases are also quite well behaved in most months.…”

Section: Results Of Applicationsupporting

confidence: 80%

Temperature tides determined with meteor radar

Hocking

Hocking²

2002

Ann. Geophys.

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Abstract.A new analysis method for producing tidal temperature parameters using meteor radar measurements is presented, and is demonstrated with data from one polar and two mid-latitude sites. The technique further develops the temperature algorithm originally introduced by Hocking (1999). That earlier method was used to produce temperature measurements over time scales of days and months, but required an empirical model for the mean temperature gradient in the mesopause region. However, when tides are present, this temperature gradient is modulated by the presence of the tides, complicating extraction of diurnal variations. Nevertheless, if the vertical wavelengths of the tides are known from wind measurements, the effects of the gradient variations can be compensated for, permitting determination of temperature tidal amplitudes and phases by meteor techniques. The basic theory is described, and results from meteor radars at Resolute Bay (Canada), London (Canada) and Albuquerque (New Mexico, USA) are shown. Our results are compared with other lidar data, computer models, fundamental tidal theory and rocket data. Phase measurements at two mid-latitude sites (Albuquerque, New Mexico, and London, Canada) show times of maximum for the diurnal temperature tide to change modestly throughout most of the year, varying generally between 0 h and 6 h, with an excursion to 12 h in June at London. The semidiurnal tide shows a larger annual variation in time of maximum, being at 2-4 h in the winter months but increasing to 9 h during the late summer and early fall. We also find that, at least at mid-latitudes, the phase of the temperature tide matches closely the phase of the meridional tide, and theoretical justification for this statement is given. We also demonstrate that this is true using the Global Scale Wave Model (Hagan et al., 1999). Median values for the temperature amplitudes for each site are in the range 5 to 6 Kelvin. Results from a more northern site (Resolute Bay) show less consistency between the wind tides and the temperature tides, supporting suggestions that the temperature tides may be zonally symmetric at these high latitudes (e.g.Correspondence to: A. Hocking (mardoc-inc@rogers.com) Walterscheid and Sivjee, 2001).

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Section: Results Of Applicationsupporting

confidence: 80%

Temperature tides determined with meteor radar

Hocking

Hocking²

2002

Ann. Geophys.

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“…The most characteristic periods of the oscillations are found to be rather uniformly spread between about 7 h and 12 h. It is interesting to note that oscillations with periods close to those of di erent tidal modes are not dominant in our results. Also having in mind the fact that all of the observed oscillations have zonal wave number one, we may conclude that the pseudo-tide mechanism, proposed by Walterscheid et al (Walterscheid et al, 1986;Sivjee et al, 1994), even if possible, is not the main mechanism which gave rise to the observed oscillations.…”

Section: Hernandezmentioning

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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“…However, the forcing of these tides-due to absorption of solar radiation in tropospheric water vapor and stratospheric ozone (the main sources for migrating tides), and latent heat release as well as convective or sensible heating-underestimates the observed amplitudes (e.g., Miyahara et al, 1993;Hagan et al, 1997). As an alternative means of generating nonmigrating tides, Walterscheid et al (1986) suggested that GW interactions with migrating tides could be important. Teitelbaum and Vial (1991) proposed nonlinear interactions between migrating tides and PWs; and the observed strong correlations between migrating diurnal and semidiurnal amplitudes and PW activity indicates that this is an important mechanism (e.g., Pancheva et al, 2002;Forbes et al, 1995;Talaat and Lieberman, 1999).…”

Section: Introductionmentioning

confidence: 97%