Nonlinear coupling between quasi 2 day wave and tides based on meteor radar observations at Maui

Abstract

[1] An observational study of nonlinear interaction between the quasi 2 day wave (QTDW) and the diurnal and semidiurnal tides from meteor radar measurements at Maui is reported. The diurnal and semidiurnal tides show a short-term variation with the QTDW activity. The variation of amplitude of the semidiurnal tide is opposite to that of the QTDW. The minimum amplitudes of the diurnal tide appear several days later than the maximum amplitudes of the QTDW, and the diurnal tide obviously strengthens when the QTDW drops to small amplitudes. The bispectrum analysis shows significant nonlinear interactions among the QDTW and the tidal components. The two quasi 16 h modes with periods of 16.2 h and 15.8 h generated in the interactions of the QTDW with the diurnal and semidiurnal tides can clearly be distinguished because of the slight deviation of the QTDW period from 48 h. The bicoherence spectrum demonstrates that the QTDW and the semidiurnal tide have quite strong levels of coherence, indicating that the nonlinear interaction is a mechanism responsible for the variability of the semidiurnal tide. Although there is also some interaction between the QTDW and the diurnal tide, their coherence level is low. When the QTDW drops to very weak amplitudes, the background wind decreases and reverses. During this time, the diurnal tide holds large amplitudes. These results support the notion that the variability of the diurnal tide is mainly attributable to the strong QTDW-induced changes in the background atmosphere, which was shown in the modeling study by Chang et al. (2011). Hence, both the nonlinear interaction and the background flow changes are responsible for the observed variation of the diurnal tide.

Observational evidence of quasi-27-day oscillation propagating from the lower atmosphere to the mesosphere over 20° N

“…A similar analysis of the meridional wind indicates that the quasi-2-day wave is a dominant component, as reported by previous studies (Zhou et al, 1997;Jacobi et al, 2001;Huang et al, 2013b), and the quasi-27-day oscillation with maximum amplitude of about 5.6 m s −1 at 86 km is much weaker than the quasi-2-day wave. According to the spacetime series of the TIMED/SABER temperature over 20 • N, we can obtain their frequency-wavenumber spectra at 82-96 km, which shows that the strongest temperature oscillation occurs at 85 km with spectral amplitude of about 2.0 K. Figure 3 presents the normalized period-wavenumber spectrum at 85 km.…”

Meteor radar quasi 2-day wave observations over 10 years at Collm (51.3° N, 13.0° E)

“…Craig and Elford (1981) explored phase locking relative to the sun and suggested nonlinear interactions with diurnal tides. This is also supported by recent studies (e.g., Huang et al, 2013a;Moudden and Forbes, 2014;Walterscheid et al, 2015). A possible correlation of QTDW amplitudes with the 11-year solar cycle has been found by Jacobi et al (1997), who explained this finding by a stronger mesospheric wind shear during solar maximum.…”

“…The period of maximum amplitude between 40 and 60 h was defined as the most probable period of the QTDW for the respective 11-day time interval. This period range is chosen in accordance with the results of Huang et al (2013a) who did not observe longer or shorter periods. Note that there are cases with more than one maximum in the selected period interval, and the lower ones are disregarded here even if they should be close to 48 h. The periodograms are calculated for the meridional component because the meridional QTDW amplitudes are observed to be larger than the zonal ones (Pancheva et al, 2004;Lilienthal and Jacobi, 2014).…”

“…The meridional component tends to be slightly larger than the zonal one at mid-latitudes (Pancheva et al, 2004) or of similar magnitude (Jacobi et al, 2001). The period of approximately 2 days varies between 43 and 56 h in the NH (Pancheva et al, 2004;Huang et al, 2013a). Generally, periods can be divided into three groups as suggested…”

Nonlinear interaction of gravity waves in a nonisothermal and dissipative atmosphere

“…These atmospheric waves propagate from the lower atmosphere to the mesosphere and lower thermosphere (MLT) and deposit their energy and momentum in the MLT due to their instability and dissipation, which has substantial dynamical effects on the large-scale circulation and thermal structure of the MLT (Lindzen, 1981;Sably, 1984). Due to the exponential decrease of the atmospheric density, atmospheric waves propagating into the MLT usually have large amplitudes, thus strong wave-wave and wave-flow interactions may frequently occur in the MLT (Fritts and Vincent, 1987;Liu and Hagan, 1998;Pancheva, 2000;Zhou et al, 2000;Jacobi et al, 2006;Chang et al, 2011;Yue et al, 2012;Huang et al, 2013a). Nonlinear interaction between planetary waves and tides is proposed as a mechanism responsible for the observed variability of tides because the beat between tides and generated secondary waves leads to modulation of tidal amplitudes at periods of planetary waves (Teitelbaum and Vial, 1991;Kamalabadi et al, 1997;Jacobi et al, 2001;Beard et al, 1999;Pancheva, 2000;Liu et al, 2007;Huang et al, 2013b).…”