CEDAR: Nonlinear Wave-Wave Induced Diurnal Tidal Variability

点击翻译按钮获取中文摘要

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.