[Houghton Lecture] Yohai Kaspi (Weizmann Institute) – Atmospheric dynamics of terrestrial planets over a wide range of orbital conditions

The atmospheric circulation of terrestrial planets emerges from the interplay between rotation, stratification, radiative forcing, and surface–atmosphere interactions. Small changes in planetary parameters such as rotation rate, atmospheric mass, planetary radius, and stellar flux can lead to fundamentally different dynamical regimes. Similarly, changes in orbital parameters such as obliquity, eccentricity and the distance from the parent star play a key role in the large-scale dynamics. In this talk, we will present a theoretical and numerical exploration of how the large-scale circulation and thermal structure of terrestrial atmospheres depend systematically on these planetary parameters. Using a hierarchy of general circulation models and scaling analyses, we identify the key non-dimensional parameters controlling the flow: the Rossby and Froude numbers, the radiative to dynamical timescale ratio, and the effective deformation radius relative to planetary size. These quantities determine whether a planet exhibits Earth-like baroclinic eddies and jet formation, Venus-like sluggish overturning, or a regime dominated by equatorial superrotation. We will discuss how variations in planetary mass influence the strength and depth of Hadley cells and the efficiency of meridional heat transport, as well as how rotation rate controls the transition between thermally direct and eddy-driven circulations. The sensitivity of the climate system to these factors reveals a coherent dynamical continuum linking Earth, Venus, Mars, Titan and terrestrial exoplanets. We will give specific examples of how open questions regarding the flow regime of Mars, Titan and Venus can be explained using this framework. Finally, we will examine how nonlinear eddy–mean flow interactions, potential vorticity mixing, and angular momentum constraints govern the equilibrium state of these atmospheres. This framework provides predictive understanding of how atmospheric dynamics scale across terrestrial worlds and offers guidance for interpreting the rapidly expanding set of exoplanet observations.

Houghton Lecture Series

Supported by the Houghton Fund, Houghton Lecturers are distinguished visitors from outside MIT, invited by the EAPS Program in Atmospheres, Oceans and Climate (PAOC) to spend a period of time, ranging from a week to several months, as scientists-in-residence.

Contact: kbauer@mit.edu