THE PROPAGATION OF INFRASONIC WAVES IN AN ISOTHERMAL ATMOSPHERE WITH CONSTANT WINDS.
AVCO CORP WILMINGTON MASS RESEARCH AND ADVANCED DEVELOPMENT DIV
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A dispersion relation for low frequency disturbances in an isothermal atmosphere with constant horizontal winds is derived which related the three components of the wave propagation vector k to the angular frequency omega and which depends on the sound speed, the wind velocity v, and the acceleration of gravity g. The relation is obtainable from that for propagation in an isothermal atmosphere without winds if omega is replaced by omega-k.v. The topology of the propagation surface in k space is examined and it is found that various modes of propagation are possible. The criteria for a given mode existing for given wind speed and frequency are derived and the group velocity of each type of mode is studied. The theory predicts the existence of two wind modes which, at sufficiently high frequencies, have group velocities nearly identical to the wind velocity. Phase velocities of the wind modes also tend to equal the wind velocity. In the latter portion of the paper, the trajectories of fluid particles are studied for each type of wave propagation mode. Author