The Study Of Atmospheric Gravity Wave Propagation Features Influenced By Background Winds

The study of propagation of atmospheric gravity wave constitutes an important part in ionosphere physics, which is significant for researching the coupling between upper and lower atmosphere, the coupling between north and south of the Earth and the coupling between ionosphere and thermosphere. In this paper, the propagation features of atmospheric gravity waves under the effect of background winds are systematically analyzed, and the influence of wind on the gravity waves propagating in the modes of both internal waves and ducted waves is further discussed.First, the conventional Ray Theory for atmospheric gravity waves is extended so that the energy attenuation along ray paths can be obtained. The directional filtering effect caused by background wind is numerically analyzed in a 2-dimensional dissipative atmosphere. And the changes of gravity wave energy attenuation and other wave parameters caused by horizontally inhomogeneous time-dependent wind are further calculated in a 3-dimensional wind model. The results are outlined as follows:(1) When propagating along wind, gravity wave ray paths with shorter wavelength are likely to be critically coupled, due to strong wind shears, and those with longer wavelength are likely to penetrate thermosphere with the ray paths being horizontally prolonged and energy attenuation increasing rapidly; When propagating against wind, ray paths with longer wavelength are likely to be reflected with a loop, which is caused by strong wind shears, whereas those with shorter wavelength are likely to be reflected without loop under the influence of positive temperature gradients as well as strong winds. And Ray paths of penetrating waves are steepened with the energy attenuation decreasing obviously. The analysis indicates that winds with different directions may cause ray paths to be prolonged, steepened, reflected or critically coupled, all of which change the accumulation of energy attenuation along ray paths. Among these rays, only the penetrating waves propagating against winds can easily reach the ionosphere height with less energy attenuation. Hence the wind...