背景风场对中尺度受导重力波的影响

采用重力波的大气分层全波解法，计算得出了强逆风场作用下以及无风条件下中尺度重力波受导波模的色散曲线和衰减距离曲线，结果表明，强逆风场可以使得各中尺度受导波模衰减距离明显变长，并导致不同尺度重力波的衰减距离出现峰值分布，通过分析美国MillstoneHill台站和武汉电离层观象中的TID实测结果证实了这些风场支持的远距离传播波模的存在。

THE INFLUENCE OF BACKGROUND WINDS ON THE PROPAGATION OF MEDIUM-SCALE DUCTED GRAVITY WAVES

The full-wave solution method in a horizonta1ly stratified atmosphere is adopted in the analysis of the propagation features of medium-scale atmospheric gravity waves, and the effect of background winds on gravity waves is considered. The dispersion and attenuation distance curves of ducted waves are calculated. The nu- merical results show that, the existence of strong background winds blowing against the propagating direction of gratrity waves can considerably prolong the attenuation distance of various ducted modes, within which mode W1 and W4 have the longest attenuation distance in short period area. Thus strong winds blowing against the propagating direction of gravity waves can support the propagation of medium- scale gravity waves. The attenuation distance decreases rapidly with the increasing of wave period, which shows that the ducted mechanism vanishes in long period range, and that the support of winds on the long-distance propagating of ducted waves is valid only in medium-scale range. The distribution in periods of Travelling Ionospheric Disturbances observed at Millstone Hill and Wuhan is statistically ana- lyzed. The result shows that the superior distribution of TIDs both in Wuhan and Millstone Hill are mainly the mode W1 and mode W4, thus the experimental results confirm the existence of these superior distributions of ducted gravity wave modes.