Validation and Impact of Large-Scale Thermospheric Gravity Waves Using ICON-MIGHTI and SD-WACCMX

Large-scale gravity waves (GWs) with zonal wavelengths of 800–5,000 km are extracted and analyzed from the Specified Dynamics version of WACCMX (SD-WACCMX) outputs from January 2020 to October 2022. First, large-scale GWs from SD-WACCMX are validated against GW observations from Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instruments on the Ionospheric Connection Explorer (ICON). Although MIGHTI GW zonal wind variances are on average 14% larger than large-scale SD-WACCMX GWs, both MIGHTI and SD-WACCMX show similar seasonal variations in the latitude range of 0°N–40°N (ICON's observational latitude range) and the altitude range of 94–150 km with semi-annual variations with peaks in December–January and July–August. On the other hand, large-scale GWs above 150 km show different seasonal variations between MIGHTI and SD-WACCMX GWs. MIGHTI GWs exhibit annual variations, and SD-WACCMX GWs are dominated by semi-annual variations. Differences are likely due to uncertainty in the simulated background winds and unresolved GW sources due to model resolutions. After comprehensive validations, this work focuses on SD-WACCMX GWs below 150 km to calculate GW drag that can affect background wind structures. The resolved large-scale GW drag can reach up to ∼15 ms⁻¹ day⁻¹, which is about 20% of parameterized GW drag in SD-WACCMX. Short-term variations in resolved large-scale GW drag can exceed ∼40 ms⁻¹ day⁻¹ during the 2021 stratospheric sudden warming.