A NUMERICAL STUDY ON THE ENERGY PROPAGATION AND CONVERSION OF GRAVITY-WAVE PACKETS EXCITED BY WAVE-LIKE DISTERBANCE IN THE MESOSPHERE

By using the spectral allocation method, the characteristics of the energy propagation and conversion in the excitation of gravity wave by an initially given Gaussian wave-like disturbance is numerically studied. The simulation results show that any single wave-like disturbance component （horizontal wind, vertical wind, density or temperature） can independently excite two gravity-wave packets, one propagates upward and another propagates downward. With the same wave parameters, the energy propagation paths of the packets under the above mentioned four kinds of disturbances are almost identical with each other and slightly different from the ray paths derived by the linear theory. A further numerical analysis indicates that the characteristic time of the energy conversion from a disturbance to a wave is almost identical for those different disturbances, equal to two times of wave period. However, the energy conversion efficiencies for different disturbances depart significantly from each other.