Geophysical and Astrophysical Fluid Dynamics

Abstract:

Finding and characterizing extrasolar Earth analogs will rely on interpretation of the planetary system's environmental context. The total budget and fractionation between C-H-O species sensitively affect the climatic and geodynamic state of terrestrial worlds, but their main delivery channels are poorly constrained. We connect numerical models of volatile chemistry and pebble coagulation in the circumstellar disk with the internal compositional evolution of planetesimals during the primary accretion phase. Our simulations demonstrate that disk chemistry and degassing from planetesimals operate on comparable timescales and can fractionate the relative abundances of major water and carbon carriers by orders of magnitude. As a result, individual planetary systems with significant planetesimal processing display increased correlation in the volatile budget of planetary building blocks relative to no internal heating. Planetesimal processing in a subset of systems increases the variance of volatile contents across planetary systems. Our simulations thus suggest that exoplanetary atmospheric compositions may provide constraints on when a specific planet formed.

Abstract:

The recently adopted Ariel ESA mission will measure the atmospheric composition of a large number of exoplanets. This information will then be used to better constrain planetary bulk compositions. While the connection between the composition of a planetary atmosphere and the bulk interior is still being investigated, the combination of the atmospheric composition with the measured mass and radius of exoplanets will push the field of exoplanet characterisation to the next level, and provide new insights of the nature of planets in our galaxy. In this white paper, we outline the ongoing activities of the interior working group of the Ariel mission, and list the desirable theoretical developments as well as the challenges in linking planetary atmospheres, bulk composition and interior structure.

Abstract:

<jats:title>Abstract</jats:title><jats:p>The global superrotation index <jats:italic>S</jats:italic> compares the integrated axial angular momentum of the atmosphere to that of a state of solid-body corotation with the underlying planet. The index <jats:italic>S</jats:italic> is similar to a zonal Rossby number, which suggests it may be a useful indicator of the circulation regime occupied by a planetary atmosphere. We investigate the utility of <jats:italic>S</jats:italic> for characterizing regimes of atmospheric circulation by running idealized Earthlike general circulation model experiments over a wide range of rotation rates Ω, 8Ω<jats:sub><jats:italic>E</jats:italic></jats:sub> to Ω<jats:sub><jats:italic>E</jats:italic></jats:sub>/512, where Ω<jats:sub><jats:italic>E</jats:italic></jats:sub> is Earth’s rotation rate, in both an axisymmetric and three-dimensional configuration. We compute <jats:italic>S</jats:italic> for each simulated circulation, and study the dependence of <jats:italic>S</jats:italic> on Ω. For all rotation rates considered, <jats:italic>S</jats:italic> is on the same order of magnitude in the 3D and axisymmetric experiments. For high rotation rates, <jats:italic>S</jats:italic> ≪ 1 and <jats:italic>S</jats:italic> ∝ Ω<jats:sup>−2</jats:sup>, while at low rotation rates <jats:italic>S</jats:italic> ≈ 1/2 = constant. By considering the limiting behavior of theoretical models for <jats:italic>S</jats:italic>, we show how the value of <jats:italic>S</jats:italic> and its local dependence on Ω can be related to the circulation regime occupied by a planetary atmosphere. Indices of <jats:italic>S</jats:italic> ≪ 1 and <jats:italic>S</jats:italic> ∝ Ω<jats:sup>−2</jats:sup> define a regime dominated by geostrophic thermal wind balance, and <jats:italic>S</jats:italic> ≈ 1/2 = constant defines a regime where the dynamics are characterized by conservation of angular momentum within a planetary-scale Hadley circulation. Indices of <jats:italic>S</jats:italic> ≫ 1 and <jats:italic>S</jats:italic> ∝ Ω<jats:sup>−2</jats:sup> define an additional regime dominated by cyclostrophic balance and strong equatorial superrotation that is not realized in our simulations.</jats:p>

Abstract:

AbstractThe global superrotation index S compares the integrated axial angular momentum of the atmosphere to that of a state of solid-body corotation with the underlying planet. The index S is similar to a zonal Rossby number, which suggests it may be a useful indicator of the circulation regime occupied by a planetary atmosphere. We investigate the utility of S for characterizing regimes of atmospheric circulation by running idealized Earthlike general circulation model experiments over a wide range of rotation rates Ω, 8ΩE to ΩE/512, where ΩE is Earth’s rotation rate, in both an axisymmetric and three-dimensional configuration. We compute S for each simulated circulation, and study the dependence of S on Ω. For all rotation rates considered, S is on the same order of magnitude in the 3D and axisymmetric experiments. For high rotation rates, S ≪ 1 and S ∝ Ω−2, while at low rotation rates S ≈ 1/2 = constant. By considering the limiting behavior of theoretical models for S, we show how the value of S and its local dependence on Ω can be related to the circulation regime occupied by a planetary atmosphere. Indices of S ≪ 1 and S ∝ Ω−2 define a regime dominated by geostrophic thermal wind balance, and S ≈ 1/2 = constant defines a regime where the dynamics are characterized by conservation of angular momentum within a planetary-scale Hadley circulation. Indices of S ≫ 1 and S ∝ Ω−2 define an additional regime dominated by cyclostrophic balance and strong equatorial superrotation that is not realized in our simulations.

Abstract:

The global superrotation index S compares the integrated axial angular momentum of the atmosphere to that of a state of solid-body corotation with the underlying planet. The index S is similar to a zonal Rossby number, which suggests it may be a useful indicator of the circulation regime occupied by a planetary atmosphere. We investigate the utility of S for characterizing regimes of atmospheric circulation by running idealized Earthlike general circulation model experiments over a wide range of rotation rates Ω, 8ΩE to ΩE/512, where ΩE is Earth’s rotation rate, in both an axisymmetric and three-dimensional configuration. We compute S for each simulated circulation, and study the dependence of S on Ω. For all rotation rates considered, S is on the same order of magnitude in the 3D and axisymmetric experiments. For high rotation rates, S ≪ 1 and S ∝ Ω−2, while at low rotation rates S ≈ 1/2 = constant. By considering the limiting behavior of theoretical models for S, we show how the value of S and its local dependence on Ω can be related to the circulation regime occupied by a planetary atmosphere. Indices of S ≪ 1 and S ∝ Ω−2 define a regime dominated by geostrophic thermal wind balance, and S ≈ 1/2 = constant defines a regime where the dynamics are characterized by conservation of angular momentum within a planetary-scale Hadley circulation. Indices of S ≫ 1 and S ∝ Ω−2 define an additional regime dominated by cyclostrophic balance and strong equatorial superrotation that is not realized in our simulations.