中高层大气潮汐波短期变化物理机制研究

As an important global scale wave phenomenon in the atmosphere, the tidal wave plays a central role in coupling from the lower to upper atmosphere.Large numbers of observations indicated that there were often short term variations in tidal waves. The mechanisms for the short term variation of tides are open questions, and the studying on the mechanisms has been received much attentions recent years. ..This project focus on the mechanisms of short term variation of tidal waves during the strong atmospheric disturbation, such as, strong planetary waves and sudden stratospheric warming (SSW) event. ..In the first step, this project plans to study the variations of tidal forcing source structure caused by strong atmospheric disturbances,such as strong planetary waves and sudden stratospheric warming (SSW), in the tidal source region. ..Then, the influences of the variation of tidal forcing source on the short term variation of the global structure of tidal wave and the generation of new tidal modes, as well as the mechanisms involved in this process will be investigated. The further study on the mechanism of the wave-wave and wave-flow non-linear interactions will be made as well...Finally, comparisons between different mechanisms are performed to understand the relative contributions of these mechanisms to the short term variations of tidal wave. These mechanisms include the variation of the tidal forcing and non-linear interations, such as, wave-wave, and wave-flow interactions...The data set used in this project are the satellite observations on the atmospheric chemistry and dynamical parameters, such as, AURA, TIMED, CHAMP, GRACE, and COSMIC satellite. The ground-based data are mainly from Chinese meridional project and interaction cooperation. The NCET data set will also be used to make analysis on the planetary waves and SSW event in the stratosphere...This project is important for understanding the process of the short term variation of tides. And it is significant for the study on the coupling from the lower to upper atmosphere.

大气潮汐波是一种大气中全球尺度的波动现象，它是从低层大气到高层大气耦合的最重要的波动之一。除了比较有规律的季节变化外，大量的观测表明大气潮汐波经常具有强烈的短期变化，对其物理机制的研究是目前大气潮汐波研究的热点问题之一。目前大量的研究主要集中在对产生潮汐波短期变化的波-波和波-流非线性相互作用的物理机制上。本项目将利用近些年对大气化学和动力学探测的全球卫星资料以及子午工程的地基探测数据，探索性研究潮汐波源区由于受到大气波动的强烈扰动而改变其波源结构，进而在短期内影响大气潮汐波的全球结构，造成大气潮汐波的短期变化以及产生新的大气潮汐波模的新的物理机制。并与已有的波-波以及波-流非线性相互作用理论进行比较研究，深入理解两种物理机制在产生大气潮汐波短期变化过程中的贡献。本项研究将加深和丰富现有的对中高层大气潮汐波短期变化物理机制的认识，对深入理解从低层大气到高层大气耦合过程具有重要的科学意义。

本项目利用近些年对大气化学和动力学探测的TIMED、Aura等全球卫星资料以及子午工程的All-Sky气辉成像仪等地基探测数据，重点研究了平流层和中间层区域的潮汐波和准定常行星波之间非线性相互作用，得到了非线性相互作用的整体特征，以及新产生的非迁移潮汐波的季节特征。研究了平流层到低热层温度中的6小时迁移潮的全球分布与季节变化特征及其激发机制，分析了大气风场水平梯度的变化对大气潮汐波变化的影响。. 结果表明，非迁移日潮、半日潮、8小时潮和6小时潮的振幅在冬季最强，夏季最弱，并与准定常行星波活动同步。在平流层和中间层区域的潮汐波和准定常行星波之间非线性相互作用是非迁移潮的一个重要源,这种非迁移潮之后传播到高中层和低热层。6小时迁移潮的振幅随高度升高而增大。在平流层中，6小时迁移潮振幅在中纬度35°N/S附近达到峰值，在70-90 km之间表现出了显著的Hough模(4,6)模的形态特征，在90 km以上除了最主要的(4,6)模外，还有其他更高阶的Hough模同时存在。6小时潮存在周期分别是年、半年、4个月和3个月的振荡，这些振荡的振幅随高度变化。在热带MLT区域，大气风场水平梯度很可能调制了相同纬度和高度处温度迁移日潮的半年、年和准两年振荡。此外，中间层的风场水平梯度可能会影响迁移日潮的垂直传播，从而使得低热层的迁移日潮具有半年变化特征。因此我们推测，MLT区域迁移日潮的半年变化很可能是由MLT区域的风场水平梯度以及中间层区域的风场水平梯度共同调制所产生的。. 本项研究加深和丰富了现有的对中高层大气潮汐波变化物理机制的认识，对深入理解从低层大气到高层大气的耦合过程具有重要的科学意义。