Planetary‐Scale Wave Impacts on the Venusian Upper Mesosphere and Lower Thermosphere. Issue 1 (26th January 2021)

• Record Type: Journal Article
• Authors: Brecht, A. S.; Bougher, S. W.; Shields, D.; Liu, H.‐L.; Lee, C.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 1(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-01-26
• Subjects: planetary waves -- thermosphere -- Venus; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2020JE006587
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: This work examines the planetary wave‐induced variability within the upper mesosphere/lower thermosphere of Venus by utilizing the Venus Thermospheric General Circulation Model (VTGCM). Rossby and Kelvin wave perturbations are driven by variations in the geopotential height of the VTGCM lower boundary (∼70 km). A suite of simulations was conducted to examine the impact of the individual and combined waves propagating from two different lower boundary conditions (uniform and varying). The Kelvin wave is the more dominant wave which produces the most variability. The combination of the Kelvin and Rossby waves provides a maximum temperature amplitude of 13 K at 92 km and maximum zonal wind amplitude of 23 m/s at 102 km. The combined waves overall are able to propagate up to 125 km. Most of the variation within the temperature, winds, and composition occurs between 70 and 110 km. The varying lower boundary increases the magnitude of the wave deposition and atmospheric responses, but weakly changes the propagation altitude. The thermal variation due to the planetary waves does not reproduce most observed variations. The simulated O2 IR nightglow emission is sensitive to the waves with respect to intensity and local time, but lacks latitudinal variation. The integrated intensity ranges from 1.2 MR to 1.65 MR and the local time ranges from 0.33 local time to 23.6 local time. Overall, planetary waves do affect the atmospheric structure, but there are still large observed variations that planetary waves alone cannot explain (i.e., thermal structure). Plain Language Summary: Venus' atmosphere has a cloud layer (∼40–∼70 km) that encompasses the whole planet that separates the lower atmosphere and upper atmosphere. Images of the clouds show planetary scale wave patterns that exist from the equator to mid‐latitudes and are thought to be a combination of Kelvin and Rossby waves. This work examines how the Kelvin and Rossby waves change the upper atmosphere by using a general circulation model of the upper atmosphere (∼70 to ∼300 km altitude). More specifically, this project analyzes the wave induced variations in temperature, winds, and a few chemical species. This work also examines how a simplified connection to the lower atmosphere changes the behavior of the Kelvin and Rossby waves and thus variations in the upper atmosphere. The results of this work demonstrate that waves provide variations between ∼70 and 110 km altitude and are sensitive to the simplified lower atmosphere connection. The wave‐induced variation does not reproduce observed thermal variations but it does reproduce observed O2 IR nightglow intensity variation. Overall, planetary waves do affect the upper atmosphere but do not propagate high enough in the atmosphere to provide all the observed variations. Key Points: Simulated planetary waves affect the atmospheric structure between 70 and 110 km, with the Kelvin wave being dominant near the equator The addition of planetary waves and a varying lower boundary can reproduce observed O2 IR nightglow emission variability in local time The simulated thermal variation due to the planetary waves does not reproduce most observed variations