CEDAR: Nonlinear Wave-Wave Induced Diurnal Tidal Variability

该项目的重点是试图确定迁移的昼夜潮汐的短期逐日变化的来源，特别关注迁移的昼夜潮汐和向西传播的Rossby重力两日波和超快开尔文波之间的非线性波-波相互作用。 迁移的日潮是中层和低热层的主要和持久的特征。 它通过水汽吸收太阳辐射而被迫进入对流层，并垂直传播到高层大气。 当潮汐垂直传播时，其结构通过与中间平均风场、行星波和耗散的相互作用而改变。 虽然观测清楚地表明，迁移的昼夜潮汐每天都有显著的变化，但迄今为止，几乎没有进行建模工作来了解这些变化的来源和影响。 目前的假设，将在这个项目中进行测试，是该机制涉及的非线性波-波之间的相互作用的迁移日潮和全球尺度的Rossby重力两天波和超快开尔文波。 将使用国家大气研究中心的热层-电离层-中间层-电动力学大气环流模型对这一假设进行研究。 TIME-GCM是一个完全非线性的三维全球环流模式，区域跨度从35到500公里。 通过进行受控的数值研究和修改模型的下边界，包括两天波和超快开尔文波的潮汐和这些波之间的非线性相互作用的潜力将被探讨。 这项研究将使人们更好地了解大气中非线性波-波相互作用的潜力，以及这些相互作用对迁移的日潮和全球尺度波的影响，如向西传播的罗斯比重力两日波和向东传播的超快开尔文波。 此外，由于迁移的昼夜潮汐可影响热层的下边界，而逐日变化将影响热层/电离层系统的天气，因此这项研究的结果将对空间天气有意义。

This project focuses on trying to identify the sources of the short-term day-to-day variability in the migrating diurnal tides, with a specific focus on nonlinear wave-wave interactions between the migrating diurnal tide and both the westward propagating Rossby-gravity two-day wave and with ultra fast Kelvin waves. The migrating diurnal tide is a dominant and persistent feature of the mesosphere and lower thermosphere. It is forced in the troposphere through the absorption of solar radiation by water vapor and propagates vertically into the upper atmosphere. As the tide propagates vertically its structure is modified through interactions with the intervening mean wind field, planetary waves and dissipation. While observations clearly show significant day-to-day variations in the migrating diurnal tide, little modeling work has been conducted to date to understand the source and impact of these variations. The current hypothesis, to be tested in this project, is that the mechanism involves the nonlinear wave-wave interactions between the migrating diurnal tide and the global scale Rossby-gravity two day wave and the ultra fast Kelvin waves. This hypothesis will be investigated using the National Center for Atmospheric Research Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM). The TIME-GCM is a fully nonlinear three-dimensional global circulation model with a domain spanning from 35 to 500 km. By conducting controlled numerical studies and modifying the lower-boundary of the model to include the two-day wave and ultra fast Kelvin wave the potential for nonlinear interaction between the tide and these waves will be explored. This research will result in an improved understanding of the potential for nonlinear wave-wave interactions in the atmosphere and the impact of these interactions on both the migrating diurnal tide and global scale waves, such as the westward propagating Rossby-gravity two-day wave and eastward propagating ultra fast Kelvin waves. Additionally, because the migrating diurnal tide can affect the lower-boundary of the thermosphere and day-to-day variations will impact the weather of the thermosphere/ionosphere system, results from this research will be of interest for space weather.