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

Abstract

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.