Numerical Modeling of Moist
Convection in Jupiter'sAtmosphere	
K. Sugiyama1,4), M. Odaka1), K. Nakajima2),
K. Kuramoto1,4), Y. Hayashi3,4)1) Hokkaido Univ., JAPAN, 2) Kyushu Univ., JAPAN3) Kobe Univ., JAPAN, 4) Center for Planetary ScienceIntroduction	

Introduction	• The mean structure of the cloud layer in Jupiter's atmosphere isthought to be maintained by the statistical contribution of a large
number of clouds driven by internal and radiative heating/coolingover multiple cloud life cycles.
• However, the mean structure and its relationship to cloud
convection has not been clarified yet.
– The thick visible clouds prevent the vertical structure of the entire
cloud layer to be observed by remote sensing.
– Galileo probe’s entry site is one of hot spots which are cloudlessregion.

– Several cloud resolving models are developed, but most of themodels have been used to simulate an onset and initial
expanding phase of a single cloud under a simplified andarbitrary initial condition (i.e., Yair et al., 1992, 1995; Hueso and Sanchez-Lavega, 2001).

• The mean vertical profiles of theatmosphere have beenillustrated by the results
obtained using one-dimensional
equilibrium cloud condensation
models (ECCM)

H2O solid– Weidenschilling and Lewis (1973)– Atreya and Romani (1985)• But, Atmospheric dynamics andcloud physical processes would
modify the features obtained by
ECCM.

Fig. Vertical structure of Jupiter’s cloudobtained by the equilibrium cloud
condensation model (Atreya et al, 1999).

Three Cloud layers!	

Pressure (Pa)Introduction	

Toward a direct simulation	
• We have been developing two-dimensional numerical models ofcloud convection that incorporates phase change and cloudmicrophysics in order to investigate the average structure of thecloud layer that is established through a large number of life
cycles of convective clouds.
– Nakajima et al. (2000) [consider H2O only]– Sugiyama et al. (2009) [consider three condensible species]
Fig: The preliminary results of numericalsimulation by Sugiyama et al. (2009).
Distribution of cloud mixing ratio (left)
and vertical velocity (right).
H 2O

The mixing ratios of H2O ice, NH4SH ice, andNH3 ice are represented using red, green, andblue color tones, respectively, and that ofmultiple composition cloud is represented by asuperposed plot of the three colors.

Our purpose	• In order to investigate idealistic characteristics of convective
motion and mean vertical structure of the cloud layer,
we perform a long-time numerical simulation of a twodimensional cloud convection model.

Model description	

Numerical model	
• Two-dimensional numerical fluid model based on the quasicompressible system (Klemp and Wilhelmson, 1978)– The system consists of the equations of motion, continuity andthermodynamic and conservation equations of condensible species.
• Radiation transfer process: Thermal forcing given as a substitute forradiative cooling.
• Cloud microphysics process: The parameterization schemes of Kessler(1969) that is well-used in Earth’s atmospheric simulation is used.

Set-up of the experiments	
• Boundary conditions• Horizontal boundary iscyclic. Stress free condition
andw = 0 are given at the lowerand upper boundaries.
• Temperature and mixing
ratios of vapor at the lowest
levelare fixed.
• Initial condition(1 x solar)	

• Random potential
temperature perturbation(Δθmax = 0.1 K) is given toseed convective motion.

Results	Results: Animation 	Temporal variation	• The convective activity of the whole layer is not steady but
quasi-periodic with a period of about 40~50 days.
• Overall temperature of thecloud layer synchronizes with
the intermittent convectiveactivity.
– We will refer the time when
the active cloud convection
occurs as `active period' (A)and the other as `quiet
period’ (Q).

Quiet period: over view (1)	• At the beginning of this quiet
period, the NH3 clouds aredistributed horizontally.
– Vertical motion is weak
(w = ~ 5 m/s)•

The vertical motion in thesub-cloud layer is the remnantof convective motion driven
during an active period.

Quiet period: over view (2)	• As time progress, NH4SH
clouds develop.
• Mixing of different
condensible gases andcondensed components acrossthe NH3 LCL or NH4SH LCL
is weak, but occurs
occasionally due to theupward or downward
penetration of convective
plumes.
– We will refer the “liftingcondensation level” as LCL	

Quiet period: over view (3)	• Following the onset ofNH4SH clouds, H2O clouds
begin to form locally.
• Mixing of different
condensible gases andcondensed components acrossthe NH3 LCL or NH4SH LCL
is still weak.

Characteristic of vertical motion 	
• NH3 LCL acts as a kinematicand compositional boundary,as does the NH4SH LCL to alesser degree.
– The horizontal-mean mixing
ratio of NH3 gas tends to beconstant between NH4SH
LCL and NH3 LCL.
– The vertical profile of w 2
has local minimum or
inflection points at the NH3
LCL and NH4SH LCL.

Active period: over view 	
• Vigorous cumulonimbus
clouds develop.
• Narrow, strong, cloudy
updrafts in the cloud layer (w ~50 m/s)

– Wide, weak, dry downdrafts(w ~ 10 m/s).

• Considerable amounts of H2O
and NH4SH condensates aretransported to the tropopause.
• Due to the vigorous verticaltransport, the mixing ratio of
each condensible gases ishighly inhomogeneous.

Characteristic of vertical motion 	• H2O condensation level acts
as a kinematic andcompositional boundary.
– The horizontal-mean mixing
ratios of all condensible
gases decrease with heightfrom the H2O condensationlevel.
– The vertical profiles of w 2has local minimum at theH2O condensation level.

Mean structure: condensed components 	
• Horizontal mean profiles averaged over several cycles including
active and quiet periods are shown.
• Considerable amounts of H2O and NH4SH cloud particles areobserved above the NH3 condensation.

ー NH3
ー H2S
ー H2O	ー NH3solid: mean
ー NH4SH broken: active periodー H2O	
dashed: quiet period	Mean structure: Condensible gases 	• The mixing ratios of NH3 and H2S start to decrease with height
not at their respective condensation levels but at the H2O
condensation level.
• The characteristics are not the same as that of the previous
thermodynamical equilibrium calculations (ECCM).
– Vertical mixing of dry and condensible during the active periods.
– condensible gases	
ー NH3ー H2S
ー H2O	

ー NH3ー NH4SH
ー H2O	

solid: mean
broken: ECCM

Mean structure: stability	• There is a distinct maximum of N2 (the square of buoyancy frequency, N) at
the H2O LCL, which explains why the level acts as both acompositional and a dynamical boundary.
– caused mainly by the change of mean molecular weight• Weaker peaks are also present at the NH3 and NH4SH LCLs,
which seem to act as dynamic and compositional boundaries to acertain extent during the quiet periods.
ー NH3ー H2S
ー H2O	

ー NH3ー NH4SH
ー H2O	

Concluding Remarks	
• We perform a long-term numerical simulation with fixed
thermal forcing• The characteristics– Active cloud convection occurs intermittently.
– The H2O condensation level acts as a steady kinematic andcompositional boundary.
– The mean vertical distribution of clouds and condensible volatiles
are distinctly different from those predicted by one-dimensional
thermodynamical equilibrium calculations.
• Considerable amounts of H2O and NH4SH cloud particles areobserved above the NH3 condensation.
• The mixing ratios of all the volatiles start to decrease with height at
H2O condensation level.