Limited hysteresis in the atmospheric dynamics of hot Jupiters

TL;DR

This study shows that hot Jupiter atmospheric circulation models quickly converge to a common state regardless of initial conditions, indicating limited hysteresis and supporting the robustness of current circulation paradigms.

Contribution

The paper demonstrates through simulations that hot Jupiter atmospheric circulation is insensitive to initial conditions, confirming the stability of the established circulation paradigm.

Findings

Circulation results are insensitive to initial wind directions and temperature profiles.

Hot Jupiter wind speeds exhibit a single characteristic value for given planetary parameters.

Limited hysteresis is observed in hot Jupiter atmospheric dynamics.

Abstract

Over the past two decades, a coherent picture has emerged of the atmospheric dynamics of hot Jupiters from a combination of three-dimensional general circulation models (GCMs) and astronomical observations. This paradigm consists of hot Jupiters being spin-synchronized due to their close-in orbit, with a resulting large day-to-night irradiation gradient driving a day-to-night temperature contrast. This day-to-night temperature contrast in turn raises day-to-night pressure gradients that are balanced by a circulation with wind speeds on the order of km~s$^{-1}$. The dominant feature of this circulation is a superrotating equatorial jet, maintained by eddy-mean flow interactions that pump momentum into the jet. In this work, I explore the dependence of this circulation paradigm on the initial thermal and dynamical conditions in atmospheric circulation models of hot Jupiters. To do so, I conduct MITgcm simulations of the atmospheric circulation of hot Jupiters with both varying initial wind directions and initial temperature profiles. I find that the results are insensitive to the initial conditions, implying that the current paradigm of hot Jupiter circulation exhibits at most limited hysteresis. I demonstrate that there is a single characteristic wind speed of hot Jupiters for given planetary and atmospheric parameters using an idealized scaling theory, and discuss implications for the interpretation of hot Jupiter observations.