Large-scale gravity wave characteristics simulated with a high-resolution global thermosphere-ionosphere model

Abstract

[1] Waves in the atmosphere, ionosphere, magnetosphere, and oceans are important mechanisms for dissipating and distributing energy throughout the Earth-atmosphere system. Internal waves are extremely important in the atmosphere, and past global studies have looked at the impacts of gravity waves on the thermosphere using gravity wave parameterizations. Here, in contrast, a medium-scale gravity wave is studied in a global thermosphere-ionosphere model, to determine the 3-D characteristics of the wave as it propagated upward through the thermosphere. The model used is a time-dependent, high-resolution, numerical model of the global thermosphere-ionosphere system, which produces global distributions of mass density, temperature, and all three components of the neutral wind at altitudes from 90 to 500 km. The gravity wave horizontal wavelengths that are measured in the thermosphere are hundreds to thousands of kilometers, with periods associated with these waves of about an hour. Therefore, a gravity wave that is physical, present in the thermosphere, and resolvable in the global numerical model was generated for this study; this wave is a 1000 km horizontal wavelength wave with a 3 h period. The gravity wave grows in amplitude, reaches a critical state and then breaks, creating curved wavefronts, and depositing its energy locally. As the gravity wave breaks, depositing its energy, a secondary wave is generated from the original gravity wave, with horizontal wavelengths of 4000 to 5000 km. The secondary wave propagates globally, unlike the original gravity wave, which only propagates in a local area. The original gravity wave had amplitudes for density and temperature of 35% and ±100 K, respectively, while the secondary wave had amplitudes of 5% and ±20 K, respectively.