Tracing low-latitude thermospheric gravity waves in a whole-atmosphere simulation to their sources

We performed a one-year long simulation using the upper-atmosphere configuration of the Icosahedral Nonhydrostatic model (UA-ICON). The simulation has a horizontal resolution of 20 km and 180 vertical levels between the ground and 150 km. At 110 km height and every hour we extracted the gravity wave vectors and amplitudes with the small-volume few-wave decomposition method S3D, which is part of the software package JUWAVE. We focus on low-latitudes, i.e. +/- 40 degrees. The model simulates clear signatures of gravity wave activity above convective hotspots over summer continents. Ray tracing shows that the largest perturbations in the thermosphere are likely primary waves from developing convection. These signatures are most prominent in waves with short horizontal scales and long vertical wavelengths. In turn, horizontally short waves with smaller vertical wavelengths cannot be traced down to the lower stratosphere. For horizontally long waves, we find a clear diurnal/longitudinal pattern in the gravity wave activity, which results from interactions with tides. The study has broad implications of how whole-atmosphere high-resolution models may help forecast thermospheric density and ionospheric perturbations, both from the numerical weather prediction perspective, as well as empirically based on known patterns of lower-atmospheric variability.