Primary versus Secondary Gravity Wave Spectra in the Thermosphere generated by Convective Sources

Abstract:

Deep convection is a significant source of atmospheric gravity waves and is particularly prevalent in the summer months over the U.S. Great Plains and Midwest owing to the formation of large Mesoscale Convective Systems (MCS). Gravity waves carry their momentum and energy from their lower atmospheric source to the upper atmosphere where they can force the mean flow and heat/cool the atmosphere through wave breaking and dissipation processes. Wave breaking and dissipation also leads to both linear and nonlinear secondary wave generation. These secondary waves can potentially propagate even higher into the atmosphere, depending upon their spectra and the ambient conditions. Total Electron Content (TEC) and 630 nm airglow observations of the Ionosphere have revealed the presence of Traveling Ionospheric Disturbances (TIDs) related to convective activity. However, it is unclear how much of the wave spectra seen at these altitudes result from primary gravity waves that travel directly up from the troposphere, and how much results from secondary wave generation in the middle and upper atmosphere. In this presentation, the 3D time-dependent, nonlinear model MAGIC is used to simulate the propagation of gravity waves generated by a convective storm system over the Midwest defined by NEXRAD precipitation rates. The simulation results are used to assess the propagation, spectral evolution, and filtering of primary and secondary waves and determine the observability of these modes in the thermosphere/ionosphere.