# Atmospheric Dynamics on Terrestrial Planets: The Seasonal Response to changes in Orbital, Rotational and Radiative Timescales

## TL;DR

This study uses an idealized climate model to explore how orbital, rotational, and radiative timescales influence seasonal climate responses and circulation patterns on terrestrial exoplanets, revealing regime transitions and empirical laws.

## Contribution

It introduces a novel analysis of seasonal climate responses to planetary parameter variations and proposes empirical power laws for Hadley circulation characteristics.

## Key findings

- Regime transition between insolation-controlled and seasonal variability-controlled climates.
- High obliquity planets with short orbital periods can have equatorial temperature minima.
- Hadley circulation width and strength depend on obliquity, orbital period, atmospheric mass, and rotation rate.

## Abstract

Thousands of exoplanets have been detected to date, and with future planned missions this tally will increase. Understanding the climate dependence on the planetary parameters is vital for the study of terrestrial exoplanet habitability. Using an idealized general circulation model with a seasonal cycle, we study the seasonal response of the surface temperature and Hadley circulation to changes in the orbital, rotational and radiative timescales. Analyzing the climate's seasonal response to variations in these timescales, we find a regime transition between planets controlled by the annual mean insolation to planets controlled by the seasonal variability depending on the relation between the length of the orbital period, obliquity and radiative timescale. Consequently, planets with obliquity greater than $54^{\circ}$ and short orbital period will have a minimum surface temperature at the equator. We also show that in specific configurations, mainly high atmospheric mass and short orbital periods, high obliquity planets can still have an equable climate. Based on the model results, we suggest an empirical power law for the ascending and descending branches of the Hadley circulation and its strength. These power laws show that the Hadley circulation becomes wider and stronger by increasing the obliquity and orbital period or by decreasing the atmospheric mass and rotation rate. Consistent with previous studies, we show that the rotation rate plays an essential role in dictating the width of the Hadley circulation.