Planetary and exoplanetary Astronomy Lunch Seminar (PALS) for 2023-01-23

Series: Planetary and exoplanetary Astronomy Lunch Seminar (PALS)
Date: Monday 23-January-2023
Time: 11:15-12:15
Location: ATL 1250
Speaker: Namrah Habib
Title: Modelling Dry Compositional Convection for Applications to Super-Earth and Sub-Neptune Exoplanet Atmospheres

Abstract: Representation of convection within 3D climate models, or General Circulation Models (GCMs), is a known source of uncertainty that affects the predicted climate and habitability of exoplanets. Convection occurs on length scales much smaller than most GCM studies resolve and is therefore parameterized. However, convection parameterizations are often tuned to Earth-based parameters or overly simplified. Additionally, in exoplanet’s with primarily H2/He atmospheres, convection can be inhibited by the greater density of atmospheric tracers compared to the background air. Previous studies have shown compositional gradients in H2/He atmospheres can cause the planetary deep atmospheric temperature to be 100s K hotter than what is conventionally predicted by a moist or dry adiabat. Hotter deep atmospheric temperatures would change our understanding of planetary interior chemistry, evolution, and habitability for terrestrial exoplanets. In this work, we aim to develop a fundamental understanding of how compositional gradients affect planetary atmospheres. We use Cloud Model 1 (CM1), a convection resolving model, to perform initial value problem testcases of non-condensing compositional convection for exoplanets with Earth-Air, H2, and CO2 atmospheres. Typically, atmospheric convection is assumed to mix the atmosphere to a global, neutrally stable atmospheric state that is only dependent on temperature. However, our CM1 simulations suggest that when there is compositional variation within planetary atmospheres, convection mixes the atmosphere to a neutrally stable state that is dependent on both the temperature and compositional profile within the atmosphere. We use our CM1 simulation results to formulate and validate a dry convective adjustment scheme for use in GCMs, which relies on an energy analysis, to determine the final adjusted atmospheric state. Overall, our convection scheme produces results that agree with our CM1 simulations and can easily be implemented in GCMs to improve modelling of compositional convection for super-Earth and sub-Neptune exoplanet atmospheres.

For further information contact PALS coordinators Quanzhi Ye at and Tad Komacek at


Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.


Directions and information about parking can be found here.

This page was automatically generated on: 10-Jan-2023.