Diurnal waves forced by horizontal convergence of near-surface winds on Mars

• Published in: Icarus (New York, N.Y. 1962) Vol. 394; p. 115420
• Main Authors: Hinson, David, Wilson, John
• Format: Journal Article
• Language: English
• Published: Ames Research Center Elsevier Inc 01.04.2023; Elsevier
• Subjects: Atmospheres, dynamics; Lunar and Planetary Science and Exploration; Mars, atmosphere; Meteorology; Mars, atmosphere; Atmospheres, dynamics; Meteorology; Dynamics Meteorology; Mars; Atmosphere Atmospheres
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2022.115420

Boundary-layer winds near steeply sloped topography excite a distinct type of atmospheric wave. Basic properties of the waves were determined through analysis of 7 Mars years of temperature profiles from the Mars Climate Sounder on Mars Reconnaissance Orbiter. A more complete understanding of the waves was derived from a simulation with the NASA Ames Mars General Circulation Model. This type of wave appears in the tropics in the vicinity of conspicuous surface features, such as large volcanoes and the rim of Isidis Planitia. The amplitude is typically 5–10 K, the vertical wavelength is about 40 km, the zonal wavelength is about 1400 km, and the zonal phase speed relative to the surface is about 25 m s−1. The wave forcing comes from horizontal convergence of the near-surface winds, which generates a daily surge in the vertical winds. These convergence zones were not previously recognized as an important source of atmospheric waves on Mars. Strong forcing occurs only within a limited range of local time, producing wave packets (diurnal pulses) rather than steady oscillations. Waves are present throughout the year and their properties vary with season. Near the solstices, the wave amplitude is largest in the tropics of the summer hemisphere, where the convergence zones are stronger than in the winter hemisphere. The diurnal-mean zonal winds, which vary with latitude and season, control the direction of propagation of the predominant waves through filtering by critical levels. •A distinct type of wave is found in Mars Climate Sounder temperature profiles.•A global model shows that the forcing comes from convergence of near-surface winds.•Convergence zones excite wave packets (a diurnal pulse) rather than continuous waves.•The waves have a zonal phase speed relative to the surface of about 25 m/s.•Some waves are trapped below critical levels while others reach high altitudes.