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Understanding the Dynamics of the Cloud-Level Atmosphere on Venus and Venus Analog Exoplanets Using a Middle Atmosphere General Circulation Model
  • Helen Parish
Helen Parish
University of California Los Angeles

Corresponding Author:hparish@g.ucla.edu

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Venus is comparable to the Earth in size and overall distance from the Sun, but is outside of a defined “habitable zone” in which water can exist in liquid form. The deep atmosphere of Venus provides a hostile environment for life. However, recent work suggests that the atmosphere at cloud altitudes, which includes regions with temperatures and pressures similar to those at the Earth’s surface, could provide possible locations for microscopic life. Since the transit method strongly favors observations of planets close to their host stars, Venus analogs may be common in exoplanet observations. With over 100 Earth-sized exoplanets observed to date, it is important to be able to identify the characteristics of Venus analogs. Thick layers of clouds, such as those which enshroud Venus, are the regions most likely to be observed on a Venus-like exoplanet. The cloud layers on Venus display a wide range of wave-related features including global scale and smaller scale gravity waves, Rossby and Kelvin waves, streak-like structures, irregular dark regions, and vortices, and show considerable variations with altitude. It is important to characterize these temporal and spatial variations to understand the dynamics of the cloud-level atmosphere on Venus or Venus-like exoplanets. Observed thermal phase curves of exoplanets may show longitudinal variations, which could indicate inhomogeneities in cloud cover, day-night differences, variations in composition, or the influence of atmospheric waves, which may shift the phase curve relative to the substellar point. To understand and interpret observations of Venus or Venus-like exoplanets at cloud altitudes, simulations have been performed using a Venus middle atmosphere general circulation model. In this investigation we simulate Rossby and Kelvin waves and modify forcing parameters, including the resolution and dissipation, and compare the results with observations from Venus probes, Venus Express and the Akatsuki mission.