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TRAPPIST Habitable Atmosphere Intercomparison (THAI) Workshop

TRAPPIST Habitable Atmosphere Intercomparison (THAI) Workshop


Context of the workshop: Upcoming telescopes such as the James Webb Space Telescope (JWST), or Extremely Large Telescope (ELTs) may soon be able to characterize the atmospheres of rocky exoplanets orbiting nearby M dwarfs. TRAPPIST-1e seems to be one of the most promising candidate to have potentially habitable surface conditions and is therefore one of the prime targets for JWST atmospheric characterization.

Modeling of its potential atmosphere is an essential step prior to observation. Global Climate Models (GCMs) offer the most detailed way to simulate planetary atmospheres. However, intrinsic differences exist between GCMs which can lead to different climate predictions and thus different observability of atmospheric features in the spectra. Such differences should preferably be known prior to observations in order to have more accurate observational constraints and to reduce model dependency while interpret the data (see the TRAPPIST-1 JWST initiative:

The TRAPPIST Habitable Atmosphere Intercomparison (THAI) have recently allowed to compare the atmospheric outputs obtained from four planetary GCMs: ExoCAM, LMD-G, ROCKE-3D and UM and their associated spectral simulations produced by the Planetary Spectrum Generator (PSG). The protocol of this intermodel comparison is available here:

Objective of the workshop: The objective of this workshop is to use THAI as a vector for comparisons and discussions between GCMs use in Exoplanetary Science to predict the climate of rocky exoplanets in the Habitable Zone, the detectability of their atmosphere (if any) and their characterization. Other Model Intercomparisons will be discussed such as the one initiated in 2019 by Jun Yang for planets at the inner edge of the Habitable Zone of M dwarfs and even the Coupled Model Intercomparison Project (CMIP), currently in its version 6, running for decades to evaluate differences in GCM responses to forcings for anthropogenic climate change on Earth. We are particularly looking for to welcome other GCM groups and users than the one currently onboard THAI, to join the discussion and contribute to the intermodel comparison and to this workshop. Along with the GCMs, Energy Balance Models (EBMs) and 1D models would also be discussed and compared within the THAI framework.

The parameterizations of convection clouds will have a central part of the discussions as they are expected to be the largest source of discrepancy between the models and that they produce a strong impact on the planetary spectra. Discussions will include -but are not limited to- the following questions:

  • What can we learn from the ongoing CMIP (members from CMIP will be present to share their experience)?
  • What did we learn from the THAI intermodel comparison effort?
  • Synergy between 3-D models and other models (1-D, EBM, Cloud Resolving Models (CRMs))?
  • What are the goals and methods that an expansion of this intermodel comparison community should adopt?

This workshop would be the first opportunity to get together many exoplanet GCM experts from different teams to discuss the important questions to tackle and the future of the field.

Few invited talks will drive the discussions around the above questions but a lot of time will be dedicated to open discussions.

To receive more info about the THAI workshop please subscribe to the email list by adding your name, affiliation and email to this google form:

Scientific Organizing Committee (SOC):
Thomas J. Fauchez (USRA / GSFC contractor)
Shawn Domagal-Goldman (NASA GSFC)
Ravi Kumar Kopparapu(NASA GSFC)
Linda Sohl (Columbia University)
Martin Turbet (Geneva Observatory, Switzerland)
Michael J. Way (NASA GISS)
Eric T. Wolf (Colorado University)

Logistic: Initially thought to be held at Columbia University, New York City, between September 14th to 16th the workshop is probably going to be fully remote at the same dates due to COVID-19. More info soon.

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