Propagation of Acoustic-Gravity Waves in Inhomogeneous Wind Flows of the Polar Atmosphere

The satellite observations of acoustic-gravity waves (AGW) in the polar atmosphere regions indicate that these waves are closely related with wind flows. This paper deals with the specific features of the propagation of acoustic-gravity waves in spatially inhomogeneous wind flows, wherein the velocity is slowly changed in the horizontal direction. A system of hydrodynamic equations taking into account the wind flow with spatial inhomogeneity is used for analysis. Unlike the system of equations written for a stationary medium (or a medium moving at a uniform velocity), the derived system contains the components describing the interaction of waves with a medium. It is shown that the effect of inhomogeneous background medium parameters can be separated from the effects of inertial forces by a special substitution of variables. An analytical expression describing the change in the amplitude of waves in a medium moving at a nonuniform velocity is derived. This expression contains two functional dependences: (1) the linear part, which is caused by the changes in the background parameters of a medium and independent of the propagation direction of waves with respect to the flow, and (2) the exponential part, which is related with inertial forces and characterizes the dependence of the amplitudes of acoustic-gravity waves on the direction of their propagation. The exponential part shows an increase in the amplitudes of waves in the headwind and a decrease in their amplitudes in the downwind. The derived theoretical dependence of the amplitudes of acoustic-gravity waves on the wind velocity is in good agreement with the data of the satellite observations of these waves in the polar atmosphere.