Other
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsa11a1556h&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SA11A-1556
Other
[0342] Atmospheric Composition And Structure / Middle Atmosphere: Energy Deposition, [3334] Atmospheric Processes / Middle Atmosphere Dynamics, [3384] Atmospheric Processes / Acoustic-Gravity Waves
Scientific paper
The gravity wave interaction is an important nonlinear effect of the dynamics of gravity waves. For prescribed wave vectors and frequencies, waves 1 and 2 may force a third wave (wave 3). If their wave vectors and frequencies satisfy the sum or difference resonant match conditions, wave 3 is excited through the sum or difference resonant interaction, otherwise, wave 3 is generated by the sum or difference nonresonant interaction. Applying a 2nd order numerical scheme, the nonlinear interaction of gravity waves in a compressible atmosphere is investigated. The numerical results show that the resonant and nonresonant interactions of gravity waves can occur indeed. A strong energy change may happen in the resonant and nonresonant interactions, which indicates that the atmospheric gravity waves with different spatial and temporal scales can extensively and frequently interact, moreover, the nonlinear interaction may play a significant role in determining the atmospheric wave spectrum. A number of numerical experiments demonstrate that in both the sun and difference resonant interactions, the wavelength and frequency of the excited wave are in good agreement with the values derived from the sun and difference resonant conditions, while the nonresonant interacting wave triad mismatches the match conditions of wavenumber and frequency. For a resonant wave triad of waves 1, 2, and 3, as long as initial waves 1 and 2 can force wave 3 through the sum resonant interaction, initial waves 3 and 1 (wave 2) can force a new wave whose wavenumber and frequency are the same as those of wave 2 (wave 1) by the difference resonant interaction, however, this does not arise for the nonresonant interactions. In both the resonant and nonresonant interactions, the energy tends to transfer mainly from the primary wave to the excited wave. Under a same secondary wave, the degree of interaction is approximately a constant value, which means that the energy of the excited wave is almost proportional to the initial energy of the primary wave. On condition that the primary waves are identical, the energy of the excited wave grows obviously with the moderate increasing of initial amplitude of the secondary wave, and even when the secondary wave has sufficient amplitude, the energy of the excited wave may be far larger than the final energy of the primary wave in both the resonant and nonresonant interactions. The main effect of the viscosity is to dissipate the energy of the interacting waves. The viscosity can hardly prevent the nonresonant excitation, suggesting that the restriction of amplitude threshold on the nonresonant interaction in the presence of viscosity predicted by the weak interaction approximation seems to be rather loose. A detuning degree of interaction is proposed, which may be applied to measure whether or not the effective energy exchange occurs in the nonlinear interactions of gravity waves. According to the analysis on the detuning degree of interaction, a more interacting phenomenon may be expected that two new gravity waves with considerable energies are simultaneously excited through the sum and difference nonlinear interactions for some special gravity wave groups if the detuning degrees of both the sum and difference interactions are small enough
Huang Kaibin
Yi Feng
Zhang Sheng
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