Explicit Global Simulation of Gravity Waves in the Thermosphere. Issue 10 (28th September 2020)

• Record Type: Journal Article
• Authors: Becker, Erich; Vadas, Sharon L.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-28
• Subjects: thermosphere -- secondary and tertiary gravity waves -- tides -- gravity wave hot spots; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028034
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We present a new version of the high‐resolution Kühlungsborn Mechanistic general Circulation Model (KMCM) extended to z ∼ 450 km. This model is called HIAMCM (HI Altitude Mechanistic general Circulation Model) and explicitly simulates gravity waves (GWs) down to horizontal wavelengths of λ h ∼ 165 km. We find predominant tertiary GWs in the winter thermosphere at middle/high latitudes. These GWs typically have horizontal wavelengths λ h ∼ 300–1, 100 km, ground‐based periods ∼ 25–90 min, and intrinsic horizontal phase speeds c I h ∼ 250–350 m s −1 . Above z ∼ 200 km, the predominant GW horizontal propagation directions are roughly against the background winds from the diurnal tide; the GWs propagate mainly poleward at midnight, eastward at 6 local time (LT), equatorward at noon, and westward at 18 LT. Wintertime GWs at z ∼ 300 km having 165 km ≤ λ h ≤ 330 km create a large hot spot over the Southern Andes/Antarctic Peninsula that agrees well with quiet time satellite measurements. Due to cancelation effects, the time‐averaged zonal mean Eliassen‐Palm flux divergence from the resolved GWs in the thermosphere is negligible compared to that of the tides and compared to the zonal component of the time‐averaged zonal mean ion drag. We also find that the thermospheric GWs dissipate mainly from macroturbulent diffusion and, above z ∼ 200 km, from molecular diffusion, whereas the tides dissipate mainly from ion drag. The averaged dissipative heating in the thermosphere due to tides is much stronger than that due to GWs. Key Points: GWs in winter thermosphere are mainly tertiary GWs generated in lower thermosphere GWs in winter thermosphere have large vertical wavelengths and propagate against background tidal winds Medium‐small‐scale GWs create hot spots in winter thermosphere like orographic hot spots in stratosphere