Abstract
By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides)
Highlights
IntroductionSince the 1960s, various aspects of linear gravity wave theories have been extensively studied (Yeh and Liu, 1974)
It is extensively accepted that the propagation of gravity waves is one of the most important and frequent kinetic phenomena that occurs in the middle and upper atmosphere
Considering three upgoing gravity wave packets as initial perturbations which take the Gaussian forms, we study the eects of nonlinearity on gravity wave packets and focus on the examination of dispersion and polarization relations in the nonlinear propagation of gravity wave packets
Summary
Since the 1960s, various aspects of linear gravity wave theories have been extensively studied (Yeh and Liu, 1974). After the 1980s, many authors have thrown light on the nonlinear eects of gravity waves and a number of valuable approaches (Lindzen, 1981; Fritts, 1984; Dewan and Good, 1986; Hines, 1991; Gardner, 1994) have been presented. Mobbs, 1987; Prusa, 1996; Zhang and Yi, 1999) In their numerical studies, they discussed many nonlinear phenomena in the propagation of gravity waves, they did not examine the validity of dispersion and polarization relations in the nonlinear region. The general discussion is given and the summary and conclusions are presented in the last section
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