Abstract
Abstract. Starting from a set of fully nonlinear equations, this paper studies that two initial gravity wave packets interact to produce a third substantial packet in a nonisothermal and dissipative atmosphere. The effects of the inhomogeneous temperature and dissipation on interaction are revealed. Numerical experiments indicate that significant energy exchange occurs through the nonlinear interaction in a nonisothermal and dissipative atmosphere. Because of the variability of wavelengths and frequencies of interacting waves, the interaction in an inhomogeneous temperature field is characterised by the nonresonance. The nonresonant three waves mismatch mainly in the vertical wavelengths, but match in the horizontal wavelengths, and their frequencies also tend to match throughout the interaction. Below 80 km, the influence of atmospheric dissipation on the interaction is rather weak due to small diffusivities. With the further propagation of wave above 80 km, the exponentially increasing atmospheric dissipation leads to the remarkable decay and slowly upward propagation of wave energy. Even so, the dissipation below 110 km is not enough to decrease the vertical wavelength of wave. The dissipation seems neither to prevent the interaction occurrence nor to prolong the period of wave energy exchange, which is different from the theoretical prediction based on the linearised equations. The match relationship and wave energy evolution in numerical experiments are helpful in further investigating interaction of gravity waves in the middle atmosphere based on experimental observations.
Highlights
Atmospheric wave perturbations include tidal, planetary and gravity waves
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)
The numerical experiments confirm that the significant nonlinear interaction can take place in a nonisothermal and dissipative atmosphere, and considerable energy is www.ann-geophys.net/32/263/2014/
Summary
Atmospheric wave perturbations include tidal, planetary and gravity waves. 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). Numerical results based on fully nonlinear model indicate that the restriction of amplitude threshold on interaction in the presence of viscous dissipation seems to be rather loose, and all interacting waves still satisfy the dispersion relation (Huang et al, 2007), which is different from the prediction of theoretical study from the linearised equations (Dong and Yeh, 1988; Yeh and Dong, 1989; Yi and Xiao, 1997).
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