OASIS

OASIS: a new 3D virtual planet laboratory built from the ground up that self-consistently couples seven individual modules representing the main physical and chemical processes that shape planetary environments. Additionally, OASIS is capable of producing simulated spectra from different instruments and observational techniques.

OASIS is being gradually improved in terms of code performance, usability and complexity in the physical modules. 

FIRST TEST 

(Mendonca & Buchhave,  accepted in Monthly Notices of the Royal Astronomical Society)

To test the OASIS platform, we produced 3D simulations of the Venus climate and its atmospheric circulation and study how the modeled atmosphere changes with various cloud covers, atmospheric heat capacity, and surface friction. By comparing the model results with observational data, we verify that OASIS is able to successfully simulate Venus. The 3D model results represent a great achievement of the OASIS platform because Venus is a challenging planet to simulate due to the long integration time required and to the need of including a computationally expensive radiative transfer code. With simulated spectra produced directly from the 3D simulations, we explore the capabilities of future missions, like LUVOIR, to observe Venus analogs located at a distance of 10 pc.

Reference Simulation
Compare To Observations
Simulated Spectra of Venus at 10 pc
OASIS Venus Animations

=> OASIS Architecture

THOR

THOR is a global circulation model that solves the three-dimensional non-hydrostatic Euler equations on an icosahedral grid (Mendonca et al. 2016). THOR is still the only model in the planetary community that has been developed from ground-up with the purpose of exploring a large diversity of planets and avoiding physical approximations brought from other research fields, such as, the Earth climate research. This model has the capacity to simulate virtual atmospheres by coupling the physics self-consistently.



CYCLOPS

CYCLOPS is a fast radiative parameterization that represents the absorption/emission/scattering by gases and clouds (Mendonca et al. 2015). The stellar radiation  calculations are based on the δ-Eddington approximation (two-stream-type) with an adding layer method (multiple-scattering). For the thermal radiation case, the code is based on an absorptivity/emissivity formulation. The formulation is implemented on GPUs and it is intended to be computationally light. This code allow us to investigate the dynamical-radiative-microphysical feedbacks on 3D simulations. The simulations typically use 353 spectral bands and 20 Gaussian points ( k-distribution).

STORM

STORM is the physics module in OASIS that represents the cloud physics. The current version is based on a radiative active tracer coupled with a cloud condensation parameterisation explored in Mendonca (2013).

 

 

ATLANTIS

ATLANTIS represents the oceans, surface and interior of planets. Currently the scheme includes: a simple Rayleigh friction to represent the mechanical interaction between the surface and the atmosphere; a coloured surface where the optical properties of the surface can be easily modified and a soil model that simulates the evolution of the temperatures in the subsurface (Mendonca & Read 2016).

LOKI

LOKI represents the small-scale turbulence in the atmosphere. Physics that happens in scales smaller than the spatial resolution of the model need to be parametrized. We include a hyper-diffusion coupled with a divergence damping scheme to represent the dissipation of kinetic energy to smaller scales. The convection is currently done with a convective adjustment scheme where the potential temperature is vertically mixed in a buoyantly unstable atmospheric column.

MERLIN

MERLIN is the atmospheric chemistry module in OASIS. MERLIN represents the chemistry in the atmosphere, surface and interior (including vulcanic outgassing).  At the moment, we can run simulations with the atmosphere in chemical equilibrium, use the relaxation method described in Tsai et al (2018) or set manually the chemical abundances in the atmosphere and surface.


GAIA

GAIA is an OASIS module that is still under-construction. This package will represent the impact of biology in planetary climates.

=> REFERENCES

Mendonca J., Buchhave L., ‘Modelling the 3D Climate of Venus with OASIS’, 2020, Volume 496, Pages 3512-3530, Monthly Notices of the Royal Astronomical Society [Link]

Tsai S., Kitzmann D., Lyons J., Mendonca J.,  Grimm S., Heng K.,  ‘Towards Consistent Modeling of Atmospheric Chemistry and Dynamics in Exoplanets: Validation and Generalization of Chemical Relaxation Method’, 2018, Volume 862, Issue 1, The Astrophysical Journal [Link]

Mendonca J. and Read P., ‘Exploring the Venus global super-rotation using a comprehensive Global Circulation Model’, 2016, Volume 134, pp 1-18, Planetary and Space Sciences. [Link]

Mendonca J., Grimm S., Grosheintz L., Heng K., ‘THOR: A New and Flexible Global Circulation Model to Explore Planetary Atmospheres’, 2016, Volume 829, Issue 2, The Astrophysical Journal. [Link]

Mendonca J., Read P., Wilson C., Lee C., ‘A new, fast and flexible radiative transfer method for Venus general circulation models’, 2015, Volume 105, p. 80-93., Planetary and Space Science. [Link]

Mendonca J., ‘Studies of Venus using a comprehensive General Circulation Model. Ph.D’, 2013, thesis, Oxford University