Cooperative studies on dynamic interactions of tides -atmospheric tides in the lower thermosphere-

本项目利用地基雷达技术研究了大气潮汐及其相关波对中高层大气的耦合过程。利用激光雷达和无线电探空仪的观测资料研究了这些波的产生和传播过程。本研究的主要部分是将雷达观测结果与日本京都的中高层大气雷达（MU雷达）、澳大利亚的阿德莱德MF雷达和加拿大的萨斯卡通MF雷达进行比较。本文首先讨论了三部雷达技术的差异对分析结果的影响，并提出了定量研究的最佳分析方法。接着我们比较了这三部雷达获得的巨大数据库，发现重力波能量在北方和南半球之间几乎是相同的量级，但在较高的纬度上较小。这一事实与目前对潮汐观测的解释相矛盾，即认为北方半球重力波活动较强，潮汐的半球差异较大，这表明今后有必要进行更多的观测和进一步的研究。我们还进行了几次三部雷达的同步观测，发现了较强的准二日波活动。然而，我们的合作研究表明，除了两天分量之外，行星波的能量要小得多。低层大气的研究表明，低纬地区可能存在潮汐的发生，通过澳大利亚、加拿大和日本等国的雷达和其他设施，我们对低层热层潮汐和相关波及其耦合过程有了更深入的了解，包括赤道地区在内的观测是今后十分重要的。

In this project, the coupling process of the middle and upper atmosphere due to atmospheric tides and associated waves is studied, by means of ground based radar technique. The observations with the lidars and radiosondes are also utilized to investigate the generation and propagation process of these waves. The major part of this study is the comparison of the radar observations with the middle and upper atmosphere radar (MU radar)in Kyoto, Japan, Adelaide MF radar in Australia and Saskatoon MF radar in Canada. Those three radar are operated regularly and with good height and time resolutions.First of all we discussed the effect of the difference of radar techniques among these three radars to the results obtained by the analysis, and developed the most useful way of the analysis for the quantitative study. Next we compared the huge database obtained with these three radars, and found that the gravity wave energy is almost same magnitude between the northern and southern hemisphere but smaller in the higher latitude. This fact contradicts to the present interpretation of the tidal observations which requires a stronger gravity wave activity in the northern hemisphere to induce a large hemispheric difference of tides, and showed the necessity of further study with more observations in future.We also carried out the simultaneous observation with these three radars for several times and found a strong activity of quasi-two day waves. However, our cooperative study has shown that the energy of the planetary waves other than two-day components are much smaller. The study of lower atmospheres indicated that the possibility of the tidal generations at the low latitude regions.In summary, we have improved our understanding of tides and associated waves in the lower thermosphere and their coupling processes by using radars and other facilities among Australia, Canada and Japan, and the observations including equatorial regions are found to be very important in future.