The LMD “Generic”
Global Climate Model:
Application toexoplanets
François Forget, Jeremy Leconte, BenjaminCharnay, Robin Wordsworth, Ehouarn Millour,
Aymeric Spiga Franck.Selsis et al. …

*CNRS, Institut Pierre Simon Laplace,
Laboratoire de Météorologie Dynamique, Paris

Modeled Cloud pattern on a tidally locked
planet around a M dwarf starLMD GCM. J. LeconteClimate Models in the solar system
What have we learned?
Mars

Lesson # 1: By many measures: GCMs work
Lesson # 2: Why and when GCMs fail(missing physical processes, non-linear processes andthreshold effects, positive feedbacks and instability, etc…)

Titan

Lesson # 3 Climate model components can beapplied without major changes to mostterrestrial planets.

TritonVenus

PlutonForget and Lebonnois (2013) In “Comparative Climatology ofTerrestrial Planets” book, Univ of Arizona press 2013.

A 3D ‘‘generic’’ Global climate model designed to simulate
any atmosphere on any terrestrial planet around any star.

1) Dynamical Core :~universal

2) Radiativetransferthrough gasand aerosols New versatile
Correlated-kradiativetransfer code.

3) Turbulence and convection in
the boundary layer
 Universal turbulent sheme Robust convection scheme5) Volatile condensation on
the surface and in theatmosphere :• Robust microphysics:
Fixing mixing ratio ofcondensation nuclei•
Modified
thermodynamics to handle
condensation of major
constituants (H2O, CO2, N2)•2-layer dynamical ocean(Codron 2011):- Ekman transport- Dynamic Sea ice4) Surface and susurface
thermal balance ~universal

A “Generic” LMD GCM for all terrestrial atmospheres:
Why simulate planets where no observations are available ?
• To Model ancient climates to understandgeological records– The faint young sun paradox on early Earth(Charnay et al. 2013)–Early Mars
(Forget et al. 2013, Wordsworth et al. 2013, Kerber et al 2014,– Ancient Titan (Charnay et al. 2014)• To simulate planets around other star todesign future telescopic measurements– Exoplanet Thermal phase curves (Selsis et al. 2011)– Constraining hot superEarth with JWST (Samuel et al., 2014)•To adress key scientific questions regarding
habitability:––Define the habitable zone
What is the probability of habitable planet in the galaxy ?

View at 8.67 µm
Ps= 1bar

Which climate on extra-solar planets ?
A hierarchy of models for planetary climatology
1. 1D global radiative convective models
 Great to explore exoplanetary climates;
still define the classical Habitable Zone
(e.g. Kasting et al. 1993, Kopparapu et al. 2013 )2. 2D Energy balance models…
3. Theoretical 3D General Circulation
model with simplified forcing: used toexplore and analyse the possible
atmospheric circulation regime andenergy transport (previous Talk by Y-Y Hayashi,see Read 2011, Showman et al. 2013, etc)

4. Full Global Climate Models aiming atbuilding “virtual” planets.

Climate, Surface liquid water and life
100% vapour

Liquid water

100% ice

Climate instability : Runaway glaciation
Solar flux↓

AlbedoTemperature↑↓

Ice and snow↑Climate Modelling: the Earth suddenly moved out by 12%(79% current insolation = the Earth 3 billions years ago)
LMD Generic Climate model, with a “dynamical slab Ocean” (Benjamin Charnay et al. JGR 2013)

ALBEDO:Climate Modelling: the Earth suddenly moved by 12%(79% current insolation = the Earth 3 billions years ago)
LMD Generic Climate model, with a “dynamical slab Ocean” (Benjamin Charnay et al. JGR 2013)

50°
C80°
C°C°C°C

40°
C°C°C°C°C°C°C

Out of glaciation: greenhouse effect
Flux = 80% present(~1.12 AU)

Present
Earth atmosphere

Charnay et al., JGR 2013

-70°C
-49°C

Out of glaciation: greenhouse effect
Flux = 80% present(~1.12 AU)-70°C[CO2] x 2.5+1°C

Charnay et al., JGR 2013

Out of glaciation: greenhouse effect
Flux = 80% present(~1.12 AU)[CO2] x 250[CH4] x 1000

10°C

+19°
CCharnay et al., JGR 2013

Minimum flux to get <Ts> > 0°C

How far can greenhouse effect can keep aplanet warm?
Kasting et al. 1993, Kopparapu et al. 2013

Rayleigh scattering> greenhouse effect1.54 AU1.62 AU1.71 AU

Pure CO2 partial pressure (bar )Scattering Greenhouse effect of CO2 ice clouds
 0°C as far as 2.5 AU from the Sun ?
Forget and Pierrehumbert (1997)

Example : Ps =10 bar
cloud opacity = 20

CO2 condensation

3D Global climate simulations of acold CO2 atmosphere(“Early Mars Case” distance equivalent to 1.75UA)

Max Warming = + 15 K
(uncomplete cloudcoverage)

CO2 ice Cloud optical depth

Forget et al. Icarus 2013,
Wordsworth et al. Icarus 2013

MAround other stars
315 in the solarStarsétoilesneighborhood:

Étoilesproches(d < 10 parsec = 32 light yearsKSunGliftetime

A Ftemperature

Glaciation around K & M dwarf stars:
Redder stellar spectrum• No albedo water ice feedback (Joshi and haberle, 2012)• Weak atmospheric Rayleigh Scaterring higher albedo
 Enhanced high pressure CO2greenhouse effect
But : Effect of tides on rotation:• Resonnant rotation with zero obliquity
 No insolation at the pole Possible Locking with permanent night sideSide Question: Are terrestrial planets in M
star habitable zone always tidally locked ?
Rocky planet on circular orbit around M stars should
synchronously rotating (Dole, 1964, Kasting et al. 1993) after~1 Gyr. However:– This does not apply to Giant planet satellites…

– Planets with eccentric orbit are likely to be in otherresonance , non-synchronous resonance (likeMercury) [e.g. Correia et al. 2008]– In presence of an atmosphere, thermal tides(resulting from solar heating of the atmosphere) canput the rotation out of synchronicity (like Venus) [Goldand Stoter, 1969, Correia and Laskar 2003, 2008, Leconte et al. 2014]

Leconte et al. Science 2014,

Example: simulating the climate on Exoplanet Gliese 581d
Super-Earth? : M sini ≈ 7 MEarh around Mdwarf (0.31 Msun)
Incident Stellar flux = 27% flux on Earth (less than Early Mars!)
Obliquity = 0°, possibly tidally locked ?

LMD Generic ModelGliese 581D

Water clouds
CO2 ice clouds
Surface temperature (K)Dry planet

Gliese 581d:
conclusions

Assuming
enough CO2 andH2O (which is notunlikely), Gliese
581d WOULD behabitable.

Wordsworth et al. 2011

With water cycle

Astrophysical Journal, Wordsworth, Forget et al. 2011

Climate, Surface liquid water and life
100% vapour

Liquid water

Climate instability at the Inner edge of hab. zone
Solar flux↑

Greenhouse effectTemperature↑↑

Evaporation↑

100% iceRunaway Greenhouse effect in 1D models(for an Earth-like planet around a sun)

Relative Solar Luminosity/Earth(Ingersoll 1969, Kasting 1988, Kasting et al. 1993, Goldblatt et al. 2013,Kopparapu et al. 2013)(at only 0.99 AU !)Impact of temperature increase on water vapor
distribution and escape: the « water loss limit »… atonly 0.99 AU from the Sun (Kopparapu, Kasting et al. 2013)
H escape, water lost to space

AltitudeExtreme UV radiation

H2O → OH +H« Photodissociation »Temperature« Water loss limit » in 1D models

Solar Luminosity/present(Ingersoll 1969, Kasting 1988, Kasting et al. 1993, Kopparapu et al. 2013)(at only 0.99 AU !)Runaway Greenhouse effect in acomplete 3D Global Climate modelLeconte et al. « 3D Increased
insolation threshold forrunaway greenhouseprocesses on Earth likeplanets". Nature, 2013

LMD 3D Generic Climate Model• Earth like planet• 64x48x30 resolution• Radiative transfer (correlated k)- 19 IR bands- 18 solar bands• Special parametrization to handle
H2O as a major constituant :• Change in Ps withcondensation/evaporation  case ofσ-P hybrid coordinates.
• Coupled system [H2O]+T+Ps

Earth like Simulation with detailed radiative transfer
in the upper atmosphere: no water loss limit !

375Wm-2
365Wm-2
353Wm-2
341Wm-2

LMD Model : Earth like planetaround a sun-like star
Leconte et al. Nature, 2013
0.97 AU
F=106% F0

0.95 AU
F=110% F0

Relative humidity

Unsaturated tropicalregions reduce thegreenhouse effect:« radiative fins »Pierrehumbert (1995), Leconte et al. (2013)

Outgoing thermal radiation

Runaway greenhouse effect aroundK and M dwarf stars
Redder stellar spectrum• Weak atmospheric Rayleigh Scaterring lower planetary albedo
Effect of tides:• Resonnant rotation with zero obliquity
 Possible Locking with permanent night side(see Leconte et al. A&A 2013, Yang et al. ApJL2013)

Cloud opacity
Simulation of aTidal-locked planet withsurface liquid water around an Mdwarf(Jeremy Leconte, LMD climate model)

Surface temperature (K)Planetary Albedo

Night side

View from a distant point throughout the orbit

The Astrophysical Journal Letters, Volume 771, Issue 2, article id. L45, 6 pp. (2013).

Tidally locked hot planets

Tidally locked hot planet: Modeling of Gliese 581c and HD85512b
S/4=860 W/m2

(250% Earth flux!) (Leconte et al. A&A 2013)• A bistable climate– Planet in “runaway greenhouse state” : with all water vapor in theatmosphere : super-hot climate– Water collapsed (frozen) on the night side.
Surface Temperature Map

Initial H2O = 250 kg/m2

Initial H2O = 150 kg/m2

Possibility of liquidwater on tidally locked
hot planet (Leconte et al.
A&A 2013)

Liquidwater
Dry

Ice

Dry
Ice

Toward a better understanding of theShabitable zone with full climate models…
F Habitable zone “Adapted “atmosphere
Plate tectonics ?

GK

 Habitable zone MKepler 186f

M
Gliese 581d

Adapted and modified from Kasting and Harman (2013)

Conclusions: Atmospheres, Climate andHabitability (1/2)•Stellar insolation•

Atmospheric compositionand surface volatile inventory•

ClimateHabitabilityRotation (rate and obliquity)
Key problem: understanding of thezoology of atmospheric composition,controlled by complex processes :• Formation of planets and atmospheres•
Escape to space•
Interaction with the surface & interior• Photochemical evolution

Can we already speculate?

For given parameters and atmospheres,
Global Climate Models are fit to explore
the climate and habitability of terrestrial
exoplanets. However, whatever the qualityof the model, heavy study of model
sensitivity to parameters will always benecessary (climate instabilities)

Expected dominant species in an terrestrial planet atmospheres (abiotic)

Stellar Flux(~ equilibrium temperature)

Forget and Leconte (2013), « Possible climate on terrestrial exoplanets »Phil. Trans. Royal Society. A. (2014) (arXiv:1311.3101)

Conclusions: Atmospheres, Climate andHabitability (2/2)•Stellar insolation•

Atmospheric compositionand surface volatile inventory•

ClimateHabitability

Rotation (rate and obliquity)
Key problem: understanding of thezoology of atmospheric composition,
controlled by complex processes :• Formation of planets and atmospheres•
Escape to space•
Interaction with the surface & interior• Photochemical evolution

 We need observations !
 We can learn a lot fromatmospheres well outside theHabitable zone

For given parameters and atmospheres,
Global Climate Models are fit to explore
the climate and habitability of terrestrial
exoplanets. However, whatever the qualityof the model, heavy study of model
sensitivity to parameters will always benecessary (climate instabilities)ありがとう ございます