Seasonal and quasi‐biennial variations in the migrating diurnal tide observed by Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED)

Abstract

[1] We present periodic variations of the migrating diurnal tide from Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) temperature and wind data from 2002 to 2007 and meteor radar data at Maui (20.75°N, 156.43°W). There are strong quasi-biennial oscillation (QBO) signatures in the amplitude of the diurnal tidal temperature in the tropical region and in the wind near ±20°. The magnitude of the QBO in the diurnal tidal amplitude reaches about 3 K in temperature and about 7 m/s (Northern Hemisphere) and 9 m/s (Southern Hemisphere) in meridional wind. The period of the diurnal tide QBO is around 24-25 months in the mesosphere but is quite variable with altitude in the stratosphere. Throughout the mesosphere, the amplitude of the diurnal tide reaches maximum during March/April of years when the QBO in lower stratospheric wind is in the eastward phase. Because the tide shows amplification only during a limited time of the year, there are not enough data yet to determine whether the tidal variation is truly biennial (24-month period) or is quasi-biennial. The semiannual (SAO) and annual oscillations (AO) in the diurnal tide support previous findings: tidal amplitude is largest around equinoxes (SAO signal) and is larger during the vernal equinox (AO signal). TIMED Sounding of the Atmosphere using Broadband Emission Radiometry (TIMED/SABER) temperature and atmospheric pressure data are used to calculate the balance wind and the tides in horizontal wind. The comparison between the calculations and the wind observed by TIMED Doppler Interferometer (TIDI) and meteor radar indicates qualitative agreement, but there are some differences as well.

Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere

“…(3). Here, we set Pr = 1 and η max = 100, 150, 200 m 2 s −1 , which are similar to previous study values of 10-1000 m 2 s −1 (Hocking, 1987;Xu et al, 2009). The total diffusion which includes both molecular diffusion and eddy diffusion is shown in Fig.…”

The diurnal and semidiurnal tides over Ascension Island (° S, 14° W) and their interaction with the stratospheric quasi-biennial oscillation: studies with meteor radar, eCMAM and WACCM

“…However, in contrast, Xu et al (2009a) came to a different conclusion about the role of gravity waves. They found that the tropical zonal wind variations associated with the QBO had little effect on the filtering of gravity waves because the effect was masked by the larger magnitude winds in the upper stratosphere.…”

“…Gurubaran et al (2009) similarly found no trace of QBO signatures in tidal amplitudes over Kauai, but found strong QBO signals in tidal amplitudes over Tirunelveli (8.7 • N, 77.8 • E). Xu et al (2009a) used SABER observations of the diurnal tide to suggest that its amplitudes are modulated by the QBO. Wu et al (2011) considered TIDI observations and reported that the semidiurnal response to the QBO was much smaller than the response of the diurnal tide.…”

Global climatological variability of quasi-two-day waves revealed by TIMED/SABER observations

“…Therefore, it has been widely applied in studies of atmospheric structures (Xu et al, 2007a, b;Dou et al, 2009;Gan et al, 2012), GWs (Preusse et al, 2006;John and Kumar, 2012), tides (Zhang et al, 2006;Pancheva et al, 2009;Xu et al, 2009) and PWs . Garcia et al (2005) and Li et al (2008) also studied QTDWs based on SABER observations.…”