Exploring planetaryatmosphereswith numericalmodeling
Aymeric SPIGA… on behalf of the
LMD planetary group

Meet the LMD team•

4.5 permanent scientists
•
•
•
•
•

102 « peer-reviewed »papers between 2007
and mid-2012

François Forget (Senior scientist, CNRS)
Sébastien Lebonnois (Scientist, CNRS)
Ehouarn Millour (Research engineer, CNRS)
Aymeric Spiga (Associate Professor, UPMC, recruited 2010)
Also: Frédéric Hourdin (Senior scientist, CNRS), Francis Codron (UPMC)• 6-10 postdoc/PhD/engineer (e.g. right now: 4 + 4 + 1)
• Institutions: CNRS, UPMC, ANR, Fondation de France, IPSL, …
• Funding from spatial agencies : CNES (FR) ESA (EU) sometime via
contracts with industry (Thales-Alenia Space, Astrium)• Many collaborations••••

France: LATMOS, LESIA, IAS, LERMA, Obs. Bordeaux, LPN, LPG
Europe: Oxford, Open University, Instituto de Astrofisica de Andalucia, INAP
USA: NASA Ames, GFDL, Brown Univ., Lawrence Livermore, Univ. of Texas
In Japan: CPS with Yoshiyuki Takahashi, to be continued!

A journey in the Solar System… and beyond
Triton NEPTUNE Pluton

Extrasolar
planets

URANUS

Titan
Saturne
JUPITER

Mars
Terre

MercureSoleilVénus

太陽系で...そして向こう旅
海王星

太陽系外の惑星

冥王星

天王星

土星
木星

火星
地球

水星

太陽

金星

小惑星帯

A journey in the Solar System… and beyond
Triton NEPTUNE Pluton

Extrasolar
planets

URANUS

Titan
Saturne
JUPITERMars= f(t)Terre= f(t)
MercureSoleilVénus

How GCMs work ? :1) 3D “Hydrodynamical core”⇒ to compute large scaleatmospheric motions and transport
2) At every grid point : Several physicalparameterizations⇒ to force the dynamic⇒ to compute the details of the local climate

Toward a “generic” Global
climate model (LMD)
ks
c
i
r
b
c»
i
r
e
n
1) Radiativeeg«transferylthrough gas
Onand aerosols3) Turbulence andconvection in theboundary layer

4) Volatile condensation on
the surface and in theatmosphere(minor/major species; seas)2) Surface
thermal inertia

Toward a “generic” Global
climate model (LMD)
1) Use parametrisations “universal”
for all planets:–––

Standard dynamical core (grid point)
Surface and subsurface thermal model“Universal” Turbulent boundary layer scheme

2) The key : Versatile, fast and accurate radiative transfer code
(see next slide)3) Simple, Robust, physically based parametrisation of volatile phasechange processes-

Including robust deep convection representation : wet convection
Clouds are represented by splitting condensed phase on a prescribed
number of Cloud Condensation Nuclei (radii  scaterring/sedimentation)
Precipitation above a threshold mixing ratio.

4) If needed: simplified physical “slab ocean + sea ice”
scheme.

Developping a Versatile, fast and accurate
radiative transfer code for GCM•

Input : assumption on the atmosphere:
–
–
–

•

Any mixture of well mixed gases (ex: CO2 + N2 + CH4 + SO2)
Add 1 variable gases (H2O). Possibly 2 or 3 (e.g. Titan)
Refractive Indexes of aerosols.

Semi automatic processes: Spectroscopic database (Hitran2008)  Line by line spectra (k-spectrum model)  correlated kcoefficients radiative transfer model•

RT Model can also simulate scattering by several kind ofaerosols (size and amount can vary in space and time)•

Key technical problems:––•

Gas spectroscopy in extreme cases
Predicting aerosol and cloud properties

Key scientific problem : assumptions on the atmosphere!

MARS

F. Forget
E. Millour
A. Spiga
L. Montabone
J.B. Madeleine+ many PhDs, postdocs,
collaborators, …

Mars climate now : atmospheric circulation, dust , CO2 (and some water)

Northern spring
CO2 ice

Water icecloudsDust

NASA/JPL/MSSS

Topography (m),Ancient terrains
Lake, rivers ??

-4.5

-4.0

AMAZONIAN : ice caps,glaciers, gullies…

-3.0

Age (Gyr)

-2.0

-1.0

Present

SEASONAL
WATER CYCLEOBSERVATIONS(MGS TES)

Ls

MODEL
(LMD GCM)

Montmessin et al. 2004, Forget et al. 2008

OBLIQUITYClimate variation in the recent past:orbit and obliquity variations

Present
During Mars History, most likely
obliquity: 41.8° (Laskar et al. 2004)

Mars water cycle at high obliquity

Richardson and Wilson 2002
Mischna et al. 2003
Levrard et al., 2004
Mischna and Richardson 2005

Solar flux

Forget et al., 2006
Madeleine et al., 2009
Levrard et al. 2007

Mars water cycle at high obliquity

Richardson and Wilson 2002
Mischna et al. 2003
Levrard et al., 2004
Mischna and Richardson 2005

Solar flux

Forget et al., 2006
Madeleine et al., 2009
Levrard et al. 2007

LMD GCM Simulations:
Water vapor column(precipitable –microns)

On present-day Mars :Same, but 45° Obliquity(Circular orbit )Ice accumulation rate (mm/yr)
high resolution simulation (2°x2°)
Obliquity = 45° , Excentricity = 0, Dust Opacity =0.2
Forget et al. Science 311, p368, 2006

mm/yr

The formation of glacier : Ice
accumulation rate (mm/yr) in a newvery high resolution simulation
Forget et al. 2006: Obliquity = 45° , Excentricity = 0, Dust Opacity =0.2

The formation of glacier : Ice
accumulation rate (mm/yr) in a newvery high resolution simulation
Forget et al. 2006: Obliquity = 45° , Excentricity = 0, Dust Opacity =0.2

•Fan shaped deposits, drop
moraines characteristic ofcold based glaciers.
•Rock glaciers
Lucchitta 1981, Head et al. 2003,
Shean et al. 2005, 2007, Head etal. 2005, Kadish et al. 2008, Schonand Head 2012

At high obliquity: Ice accumulation by
ice precipitation on windward slope

High Obliquity Simulation with awater ice cap at the south pole
(Forget et al. 2005)

Yearly accumulation rate

(mm/year) (1Oth year simulation)

Summertime
water vapor flux

GCM simulation

Head et al.
Hartmann etal.
Crown et al.
Etc…

Back from high obliquity to low obliquity

Levrard et al. (2004)

Impact of obliquity on SUBSURFACE ice stability
Obliquity increases : More water vapor : ice more stable Mean temperature and summer temperature increase :ice less stable

Stableice

Ice stability(<Tfrost> - <Tsurf>(Schorghofer 2007 criterion)

Forget et al. 2007

Early Mars Climate

François Forget, Robin Wordsworth,Ehouarn Millour, Jean-Baptiste
Madeleine, Benjamin Charnay,
Vincent Eymet and Bob Haberle

More and more observations
suggesting that « early Mars » wasdifferent, with flowing liquid water,
possibly precipitation:
Only in ancient terrains:
Valley networks• High Erosion rate in very ancient terrains• Layers, « Lacustrine » deposits, deltas• Mineralogy related to water alteration :• Clays (detected by Mars Express Omega): in very ancient•terrains

Sulfate (detected by Omega & MER): less ancient terrains• Hematite(detected by MGS TES)
• Silica (Opal) (Spirit)•

Early Mars: a completely different world!
CO2-CO2 collision-induced
absorption was overestimatedNew parametrisation

CO2 ice clouds warming
15 to 20K

 Reduced CO2 greenhouse effect !
(Wordsworth et al. Icarus 2010)

Forget and Pierrehumbert 1997

0.5 barSurface
CO2 ice5 bar

3D initial conditions for H2O
water ocean

2 bar,ocean

5 bar,ocean

5 bars of CO2 ???
Initial Mars inventory > 10 bars (probably)
BUT recent studies suggest a much thinner inventory for
the Noachian Martian atmosphere:– Primordial atmosphere maybe removed quickly (Tian et al., 2009)– Tharsis outgassing probably overestimated. Morschhauser 2011
– After heavy bombardment, weak atm. escape (Lammer et al. 2011) 500 mbar of CO2 may be an upper limit on ancient
Mars ? . It will still be very different than today :• Cold traps in the mountains (like on Earth)• Liquid water much more stable• Larger ice inventory ? (less ice sequestered?)• Some greenhouse effectMars with ~500 mbar of CO2
Starting with limited polar caps:
Surface ice (kg/m2) : initial state  same after 50 years
Ps = 0.5 bar obliquity=25°

Mars with ~500 mbar of CO2
Starting with limited polar caps: HIGHER obliquity (45°)
Surface ice (kg/m2) : AFTER 50 years
Ps = 0.5 bar obliquity=45°

Starting with limited polar caps: REMOVING THARSIS
Next step: remove the LHB basin
Surface ice (kg/m2) : AFTER 50 years
Ps = 0.5 bar obliquity=25°

VENUS

S. Lebonnois+
Manycollaborators

Grid-point

Zonal
wind
(m s-1)

Altitude

Venus is anextreme case fordynamical
cores given its
slow forcings

Spectral

CCSR (Japan)

LMD

Open Un.

OxfordLR10s

LR10-fd

Intercomparison
Lebonnois et al. 2012
All models are run with a simple
Newtonian relaxation!

Finite Volumes
UCLA

LR10-fv

LatitudeObservations of superrotation
Pioneer Venus andVenera probes

VENUS
70 km
60 km
50 km

Venus Express/VIRTIS cloud tracking

The superrotation question
Superrotation at the equator:
need for non­axisymmetric planetary waves
Jet, super­rotation
Planetary waves
angular momentum
transport
Equatorial super­rotation

Angular momentum transport
MMC transport
Annual mean

Transients transportVenus Superrotation

CloudsStarting from rest

Mean zonal wind and stream function after 1000+ Vdays(Topography, diurnal cycle)

Role of the diurnal cycle

Without diurnal cycle
With diurnal cycle
Influence of thermal tides inangular momentum transport:
downward transport in theequatorial 64­90 km region.

Discussion
Tides

Transients

MMC
Mountain torqueSurface friction

Additional aspect: Titan vs Venus: the influence of seasonal variations.

Examples of such impacts
PBL scheme in Venus simulations :Mellor & Yamada (1982) scheme

Previous scheme(Lebonnois et al 2010)

Examples of such impacts
Topography in Venus simulations :With topography

Without topography

Examples of such impacts
Initial conditions in Venus simulations :Started from rest

Started from realistic wind profile

Gravity waves

Clouds

Impact on the simulation started from superrotation

Closer to observations, though cloud­bottom to cloud­top gradientstill too strong.

Temperature meridional distribution
0.5
1

10

VIRTIS, Venus Express

100

500
p(mbar)

VeRa, Venus ExpressTemperature meridional distribution
LMDZ­Venus

0.5

(Pa
)

1

10

VIRTIS, Venus Express

100

500
p(mbar)

VeRa, Venus ExpressTitanS. Lebonnois
B. Charnay
F. Hourdin
P. Rannou…

Main characteristics of Titan’s
atmosphere• Super-rotation• Methane cycle• One Hadley cell. Equinox reversal• Radiative time scale ∼ 2.5 Titan years• Weak diurnal cycle (∆Ts < 1 K)
• Circulation ~ Mean circulation• Pressure influenced by gravitational
tides induced by SaturnLower troposphere and boundary layer of Titan
Charnay & Lebonnois, Nature Geoscience (2012)
Thermal structure

Diurnal cycle of boundary layer• Boundary layer forced by diurnal cycle, up to 2 km @ ITCZ
• Hadley cell confined in the lowermost 2 km
 additional boundary layer circulation

Formation of giant dunes

Andreotti et al., Nature (2009)
PBL controls size & spacing of giant
dunes: λ≈H
Dune spacing on Titan ≈ 3 km
Agreement with a PBL 2-3 km deep (Lorenz et al, 2010)

Thermal structure compatible
with 2 km-deep PBL  explainsdune size and spacing.
Charnay & Lebonnois (2012)

Dune orientation
Equator  direction opposed to mean zonal wind in GCMs!

Why
GCM winds
are opposed todune winds?
• Either: an important atmospheric process is
missing (topography, methane cycle, …)• Or: dunes do not form by saltation; dunes are
paleo-dunes (different climate) ; …

Convective storms at the equator at equinoxes
Turtle et al (2010,2011)

Could be reproduced by GCMs
Schneider et al (2011)

Possible dust storms on Titan

Rodriguez et al, LPI 2012

Observations of superrotation
TITAN
Huygens/DWE verticalprofile at 10°S (Ls ~ 300°)

Cassini/CIRS thermal winds
retrieval (Ls ~ 300°)

Titan Superrotation
Started from 2D­CM simulations,interactive haze

Mean zonal wind and stream function after 12 Titan years

Pluto and Triton
Triton Ps=1.4 Pa (N2) observed by Voyager 2 (1989)
First GCM : retro-super-rotation; observed winds explained
Seasonal model for ices (run over 3000 years!)Pluton Ps= 2Pa (N2 + 0,5% CH4)First complete GCM
Circulation , methane cycle, organic haze
Preparation of the NASA New Horizons mission→

New Horizons. Flyby of
Pluto on July14th, 2015

Archean Earth

Benjamin Charnay, François Forget, Robin
Wordsworth, Jérémy Leconte, Ehouarn Millour,
Francis Codron and Aymeric Spiga

Observations (Reanalysis)

LMDZ Generic<Tsurf>=14.7°C<Tsurf>=14.7°C

The faint young Sun paradox:• Sun 20-25% weaker during the Archean• Geological evidence for liquid water and primitive life
• Need for warming processes

Solutions:

A reduced
planetary albedo• less lands• larger cloud droplet

Greenhouse gases
• C02
• CH4
• NH3
•…

Other effects• higher atmosphericpressure• faster rotation

Can we get a temperate early Earthwith the geological constraints?
Maximal partial pressure of CO2 at 2.5 Ga: 0.01-0.02 bar
Maximal haze free CH4/CO2 ratio: 0.1-0.3

Climate obtained with present day lands(simulations at 2.5 Ga with C02=0.01 bar; CH4=2 mb)<Tsurf>=10.5°C• Colder climate than today• Continental ices at high latitudes• Maybe acceptable with geological constraints

Climates obtained with different lands(simulations at 2.5 Ga with C02=0.01 bar; CH4=2 mb)<Tsurf>=10.5°C<Tsurf>=11.5°C<Tsurf>=13.7°C• ∆Tsurf=0-3°C• Case with supercontinent fully acceptable

Effect of greenhouse gases

Conditions for temperate climates:
Late-Archean: CO2=0.01 b and CH4=2 mb
Earlier Archean: CO2=0.1 b and CH4=2 mb

Effect of cloud droplet size on surface temperature

C02=10 mb;
CH4=2 mb

C02=0.9 mb;
CH4=0.9 mb∆Tsurf=5-10°C

Effect of atmospheric pressure(simulations at 3 Ga with C02=0.01 bar; CH4=2 mb; N2=1-2 bar)Temperature lapse rate

Temperature profile∆Tsurf=4-8°C

Effect of the rotation period
Earth’s rotation period at 4 Ga ≈ 14h
Tidal friction rised it to 24h now.

1

Meridional transport ∝2Ω(Stones 1972)• Colder poles/warmer equator• Possible effects on cloud
covering (Jenkins 1995)

With our GCM:
• Cooling of less than 1 K for
temperate climates• Warming for cold climatesCase of a cold early EarthCold climates and waterbelts(simulations at 3.8 Ga with C02=0.9 mb; CH4=0.9 mb; no land)
P=24h

P=14h

<Tsurf> = -18°C<Tsurf> = -15°C

Hot climates(simulations at 3.8 Ga with r=17 microns and no land)Composition<Tsurf>Precipitable water

AlbedoN2=0.9 b; CO2=0.1 b; CH4=2 mb

27.5 °C

40 kg/m20.25

N2=0.5 b; CO2=0.5 b; CH4=1 mb

56 °C

280 kg/m2

0.24

N2=1 b; CO2=1 b; CH4=2 mb

70.5 °C

470 kg/m2

0.22

Simulating exoplanetaryatmospheres:
Living beyond the
runaway greenhouse limit
Jeremy Leconte
Francois Forget , Robin Wordsworth, B.
Charnay, E. Millour, F. Codron, A. Spiga , F
Selsis, V. Eymet
LMD, Institut Pierre Simon Laplace, Université Pierre et Marie
Curie, BP 99, 75005 Paris, FranceWhat we have learned from solar
system GCMs•

To first order: GCMs work–•

A few equations can build « planet simulators » with a realistic,
complex behaviour and strong prediction capacities

However Problems with :•••Missing physical processes (e.g. radiative effects of Martian clouds)
Positive feedbacks and unstability (e.g. ice albedo feedback on the Earth)
Non linear behaviour and threshold effect (e.g. dust storms on Mars)•

Complex, large System with small forcing (e.g. Venus circulation).
initial state•

Complex subgrid scale process and poorly known physics (e.g. clouds on
the Earth, Gravity waves on Venus)=> whatever the quality of the model, heavy
study of model sensitivity to parameters will
always be necessary.

/Sensitivity toRoaming the Habitable zone

Warm terrestrial
atmospheresb

HD85512The goal is not only to model agiven planet climate!

Selsis et al. 2007

1D vs D3: systematic biases
350

1D

Gl 581 c

Systematic
1D/3D
discrepancy

Temperature HKL

300

Ê
Ê
‡

Mean

250 Ê
‡

Ê

Ê Ê Ê
‡
‡ ‡

Ê
‡

Ê
‡

HD 85512 b

·
Á

Á

200
·

150

·

Á

Á

·

·

Á Á

·
Á

·

Min

Á

Á

100

1
T̄s =
4⇡

Z 2⇡
0

d

0.1

Z 1
0

0.2

d cos ✓?

0.5

✓

1.0

ps HbarL

(1

2.0

5.0

10.0

A) F? cos ✓?
SB

◆1/4

p

2 2
=
T̄equ
5

wind maps (m/s)~4km Altitude- 180.

- 90.

0.

90.

latitude H°L

60402080

60
120 80

20

100
- 90.

20

longitude H°L
0.

10
45.

- 45.

30
20

HD85512b

latitude H°L

Slow
Gl 581 c

45.

- 90.

30

longitude H°L
0.

90.

20
- 45.

10

- 90.

20
longitude H°L
0.

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5
5 10

25
20

45.
0.

20
- 45.

10

10

- 90.

15
90.
90.

180.
180.
90.

p =900.mb

5 45.
25 15
10
20

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- 180.

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90.90.

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20

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60
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p =200.mb

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- 90.
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--180.
0.
90.90.
longitude H°L
p =200.mb

latitude H°L

-180.
180.
90.

- 90.

60

60

100

Gl581c0.

40 20

latitude H°L

latitude H°L

120

120

- 180.
90.90.

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120 80510045.45.

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p =200.mb

80604020- 90.

latitude H°L

HD 85512 b

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90.
45.

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longitude H°L
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Can these planet bear liquid water?
Liquid water

Ice Flows

Cl
ds
ou

North
Pole

Dry groundvapor

Ice cap

Like on Earth, if a thick ice cap is present (a few km),Ice flows and subsurface water could exist.

SATURN and GIANT PLANETS
A. Spiga
with
T. Fouchet
S. Guerlet
M. Sylvestre
E. Millour

Cassini

EmerGéantes : a new Saturn GCM
A lot of challenges!
A change ofscalesDifferent planetary
constants

No surface+ internal heat flux

Unusual radiative
forcings

Numerous applications
Application 1
Dynamical enigma in the Saturn stratosphere
Application 2
Comparative planetology
Application 3
Exoplanets : hot Jupiters

HD 189733 b

Development of a first prototype●●●

P=0,03 mbar

Main ingredients: absorption by CH4,
thermal emission by CH4, C2H6,
C2H2, H2/He continuum.
We use correlated-k distributions.
Radiative transfer tested in a 1D setup of the GCM: typical temperature
profile well reproducedFirst 3D test runs in progress

P=0,66 bar
Temperature

Goal: Present first results at EPSC and DPS 2013 !
CIRS Meeting, 6-8 Feb. 201313

Lundi 7 janvier

11

A recipe for our work
1. Exploration and fun (but we are very serious about our work)
2. New models adapted from existing « bricks » from past projects
3. Benefit from Earth climate modeling at LMD
4. Excellent young students, post-docs, engineers…
5. LOTS of collaborations, and not only atmospheric scientists
6. Strong link to spatial programs, missions, instruments

Lundi 7 janvier

12

A recipe for our work
1. Exploration and fun (but we are very serious about our work)
2. New models adapted from existing « bricks » from past projects
3. Benefit from Earth climate modeling at LMD
4. Excellent young students, post-docs, engineers…
5. LOTS of collaborations, and not only atmospheric scientists
6. Strong link to spatial programs, missions, instruments
7. French wine

あなたの温かいおもてなしとご関心をお寄せいただきあ
りがとうござい
Aymeric SPIGA
えめりく すぴが