Global thermodynamic, transport-property and dynamic characteristics of the Venus lower atmosphere below the cloud layer

Abstract

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Turbulent chemical-species mixing in the Venus lower atmosphere at different altitudes: a direct numerical simulation study relevant to understanding species spatial distribution

“…For example, while it has been proposed that species separation occurs (Lebonnois and Schubert, 2017) as noted by Limaye et al (2018), experimental studies meant to probe this assumption remain inconclusive (Lebonnois et al, 2020). At least one modeling and numerical study (Cordier et al, 2019) concludes that molecular diffusion is very inefficient so that it could not be responsible for the hypothesized separation of N 2 and CO 2 , and that phase separation is also very unlikely, a conclusion in concert with more recent findings (Morellina et al, 2020). However, the study of Cordier et al (2019) exclusively utilized thermodynamics and molecular dynamics, and thus one may question these conclusions given that thermodynamics is inappropriate for computing gradients which are the indicators of species distribution, and therefore of potential separation, and that molecular dynamics relies on the knowledge of a molecular potential, and this potential must be appropriate for high-pressure (high-) situations, as is for example the ReaxFF potential (van Duin et al, 2001).…”

“…Johnson and de Oliveira, 2019, Jacobson et al, 2017, Morellina et al, 2020 reveals increasingly detailed information regarding the global thermodynamic and dynamic conditions up to approximately 50 km of altitude. The knowledge of the chemical composition, as provided by species mass fraction provided within a range of values for each species (Jacobson et al, 2017, Johnson andde Oliveira, 2019), together with the information regarding the temperature,  , and pressure, , allowed the computation of a multitude of other characteristics of the Venus lower atmosphere (Morellina et al, 2020). For example, transport properties such as chemical mixture viscosity,  and thermal conductivity,  were calculated according to high-pressure (high-) models (Reid et al, 1987).…”

“…Compared to the study of Morellina et al (2020), the present investigation is an additional step towards developing a formulation for the description of the entire Venus lower atmosphere that will be time-dependent, 3D and not rely on parametrizations from Venus atmosphere observations. Bierson and Zhang (2020) conclusively show that no parametrization is reliable for explaining the variations of all species in the Venus atmosphere.…”

Closing the Gap Between Theory and Observations of Venus Atmospheric Dynamics with New Measurements

“…The current understanding of the zonal super-rotating atmosphere is mainly derived from the, Soviet Union Venera and VEGA missions, NASA Pioneer Venus mission (PVO), and the ESA Venus Express mission (VEX) with augmentations from the current JAXA Akatsuki mission (cf. Gérard et al, 2017;Horinouchi et al, 2020;Imamura et al, 2020;Morellina et al, 2020;Read & Lebonnois, 2018;Sánchez-Lavega et al, 2017). For simplicity of explanation within this white paper, the zonal atmospheric flow is broken up into 3 zones based upon observations and shown in Figure1.…”

A Recharge Oscillator Model for Interannual Variability in Venus’ Clouds

“…Note that we have not made a distinction between thermal and momentum eddy diffusivities and the above value is derived from thermal considerations (layer height depends on cloud‐base temperature, as defined in Section 2.1) but is used for estimating dynamical mixing of chemical species. Since the Prandtl number, which is the ratio of the momentum to the thermal diffusivity is of order unity and does not vary much with altitude from 45 to 60 km on Venus (Morellina et al., 2020), using a single value of eddy diffusivity for both is a crude but acceptable simplification. The relationship derived above indicates that higher thermal heating flux at the cloud base (represented by a larger convective layer height) leads to a higher eddy diffusivity, which is consistent with other numerical studies of eddy mixing in the Venus cloud layer (Yamamoto, 2014).…”