Effects of Initial Flow on Close-In Planet Atmospheric Circulation

TL;DR

This study demonstrates that initial atmospheric flow conditions significantly influence the 3-D circulation and temperature patterns on tidally locked exoplanets, challenging assumptions of model robustness in current climate simulations.

Contribution

It highlights the critical impact of initial flow states on atmospheric circulation outcomes in 3-D models of tidally synchronized exoplanets, an aspect previously underexplored.

Findings

Different initial states lead to distinct flow and temperature distributions.

Coherent jets and vortices evolve differently depending on initial conditions.

Circulation models are currently unreliable for precise predictions without well-constrained initial states.

Abstract

We use a general circulation model to study the three-dimensional (3-D) flow and temperature distributions of atmospheres on tidally synchronized extrasolar planets. In this work, we focus on the sensitivity of the evolution to the initial flow state, which has not received much attention in 3-D modeling studies. We find that different initial states lead to markedly different distributions-even under the application of strong forcing (large day-night temperature difference with a short "thermal drag time") that may be representative of close-in planets. This is in contrast with the results or assumptions of many published studies. In general, coherent jets and vortices (and their associated temperature distributions) characterize the flow, and they evolve differently in time, depending on the initial condition. If the coherent structures reach a quasi- stationary state, their spatial locations still vary. The result underlines the fact that circulation models are currently unsuitable for making quantitative predictions (e.g., location and size of a "hot spot") without better constrained, and well posed, initial conditions.