CEDAR: Nonlinear Wave-Wave Induced Diurnal Tidal Variability

本项目的重点是确定迁移日潮的短期日变率的来源，特别关注迁移日潮与向西传播的ross - by-gravity日波和超高速开尔文波之间的非线性波-波相互作用。日潮的迁移是中间层和低层热层的主要和持久的特征。它通过水蒸气吸收太阳辐射而被迫进入对流层，并垂直传播到上层大气。当潮汐垂直传播时，它的结构通过与中间的平均风场、行星波和耗散的相互作用而改变。虽然观测清楚地表明，日潮的迁移有显著的日变化，但迄今为止，很少进行建模工作来了解这些变化的来源和影响。目前的假设是，该机制涉及迁移日潮与全球尺度ross - by-gravity两日波和超高速开尔文波之间的非线性波-波相互作用。这一假设将使用国家大气研究中心的热层-电离层-中间层-电动力学环流模型（TIME-GCM）进行调查。TIME-GCM是一个完全非线性的三维全球环流模式，其区域跨度为35 ~ 500 km。通过控制数值研究和修改模型的下界以包括两天波和超快开尔文波，将探索潮汐与这些波之间非线性相互作用的潜力。这项研究将有助于我们更好地理解大气中非线性波-波相互作用的潜力，以及这些相互作用对迁移日潮汐和全球尺度波的影响，如向西传播的罗斯重力两天波和向东传播的超高速开尔文波。此外，由于日潮的迁移可以影响热层的下边界，日变化将影响热层/电离层系统的天气，因此本研究的结果将对空间天气产生重要影响。

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.