Radiative Heat Balances in
Jupiter’s Stratosphere:
Development of a Radiation Codefor the Implementation to a GCM

T. Kuroda

Tohoku University

A.S. Medvedev, P. HartoghMax Planck Institute for Solar System ResearchWhy Jupiter?
Towards the universal understandings ofobjects in the space (terrestrial planets,gas giants, brown dwarfs, stars…)• For universal understandings of formation and evolution ofplanetary atmospheric circulations, with different viewpoints
from the investigations of terrestrial planets.
(clarifications of physical parameters specific to each planet)• The field of planetary science is broadening beyond our solar
system, and gas giants are especially important in extra-solar
stellar systems as far as our current understandings.
Then we need to understand Jupiter, the closest gas giant to us,
thoroughly as the first step.

Atmosphere of Jupiter
Vertical structure: observed by Galileo Probe• Thermosphere(<10-3hPa)• Stratosphere(102～10-3hPa)• Troposphere(104-5～102hPa)- With cloud layers- Driven by theinternal heat source.

[Seiff et al., 1998]

Here we focus on the stratosphere.

JUICE-SWI (sub-millimeter instrument)• The main objective of a sub-millimetre
wave instrument is to investigate thestructure, composition and dynamics ofthe middle atmosphere of Jupiter andexospheres of its moons, as well as
thermophysical properties of thesatellites surfaces. (from Yellow Book)• JUICE-SWI is highly sensitive for CH4, H2O,HCN, CO and CS in Jupiter’s stratosphere.
• From CH4 molecular lines, verticaltemperature profiles and wind velocities
can be detected.
• CO and CS, which are chemically stable,
can be used as tracers for the investigations of atmospheric flows (generalcirculation and dynamical processes).

PI: P. Hartogh (MPS)
Chosen for the JUICE
mission! (02/21/2013)

Collision of
ShoemakerLevy 9[HST, 1994]:
Origin of
H2O, CS, COand HCN?

Jupiter’s stratosphere

Temoperature and zonal
wind fields observed by
Cassini/CIRS• Affected by radiative processes
by molecules in stratosphere andeddies enhanced from thetroposphere.
(cf. troposphere: convection cellstructures transport the energy
and momentum)• The estimation from the thermal
wind equation and cloud tracking(for lower boundary wind speed)
shows the existence of fast zonal
wind jets of 60-140 m s-1 at 23N
and 5N.
[Flasar et al., 2004]

Radiative processes of Jupiter’s
Mixing ratios ofstratospherehydrocarbons from a• CH4: Absorber of the solar radiation• CH4, C2H2, C2H6, collision-induced
transitions of H2-H2 and H2-He:
Effective in the infrared cooling.
We have developed a band radiativetransfer model for Jupiter’s
stratosphere for the fast and effective
calculations in the GCM (correlated kdistribution approach).

photochemical model[Moses et al., 2005]

Here we show the numerical results for heating/cooling rates calculated
from 1-D profiles of temperatures and composition, in comparison
between correlated k-distribution and line-by-line approaches.

Calculations
Molecules

Lines (1hPa, 150K) considered for thecalculations (infrared: 10-2000 cm-1)
Collision-induced transitions(proportionalto pressure)• Molecular lines of CH4, C2H2 (600-860 cm-1) and C2H6 (700-960 cm-1):
From HITRAN2008 [Rothman et al., 2009] with update for C2H6 (in2009) and C2H2 (in 2011).
• Voigt profile is used for the calculation of line spectrum, with wing
cutoff of 25 cm-1 for all molecules.
• Collision-induced transitions of H2-H2 and H2-He: From Borysow[2002] (H2-H2) and Borysow et al. [1988] (H2-He).

Calculations
CH4 (near-infrared)

Lines (1hPa, 150K) considered for thecalculations (solar: 2000-11800 cm-1)
CH4(visible)(constant topressure andtemperature)• Molecular lines of CH4 (2000-9200 cm-1): From HITRAN2008.
• Voigt profile is used for the calculation of line spectrum, with wing
cutoff of 25 cm-1 for all molecules.
• CH4 line spectrum in visible wavelength (10800-11800 cm-1): From
O’Brien and Cao [2002].
• Between 960 and 2000 cm-1, both the solar absorption and infraredemission are considered.

Calculations

CH4 line spectrum(3300-4800 cm-1)

k-distribution [e.g. Liou, 2002]
k-distribution of
the line spectrum• For fast calculations of fluxes, the line spectrum in each band isordered to be a monotone increasing function.
• In our band model, the absorption and emission by molecules ineach band are calculated with 12 k-distribution integration points.

Calculations

Coordinate of the band modelBand

IR(infrared)/SO(solar)

Wavenumber
range [cm-1]

Molecules

12
3
45678
910111213
1415
1617IRIRIRIRIR
IR
IR, SO
IR, SO
IR, SO
IR, SO
SO
SO
SO
SO
SO
SO

10-150150-300
300-600
600-700
700-860
860-960
960-1200
1200-1400
1400-1600
1600-2000
2000-3300
3300-4800
4800-6300
6300-7800
7800-9200
9200-10800
10800-11800

CH4, CIT
CH4, CIT
CH4, CIT
CH4, C2H2, CIT
C2H2, C2H6, CIT
CH4, C2H6, CIT
CH4, CIT
CH4, CIT
CH4, CIT
CH4, CITCH4
CH4CH4CH4CH4CH4• Correlated k-distribution
approach• We made a table of kdistributions in 13
pressure grids (log-equalinterval between 10-3 and103 hPa), 3 temperature
grids (100, 150 and 200 K)
for 17 wavenumber bands.

• The atmospheric composition of molecules (1000 ppmv of CH4, 1
ppmv of C2H2, 10 ppmv of C2H6, 89.8 % of H2, 10.2 % of He) is fixedin making the table.

Calculations
Temperature

Considered vertical profiles oftemperature and composition
Component• Temperature: Galileo Probe [Seiff et al., 1998] (Profile 1)
Voyager radio occultation [Lindal et al., 1981] and linear
extrapolation (Profile 2)• Component: From 1-D photochemical model [Moses et al., 2005]• Calculation of solar radiation: Assumed zenith angle of 0°

Results

Solid: Band
Dashed: Line-by-line

Heating/cooling rates(Profile 1)• Differences between band and lineby-line calculations are very small.
• Mid- and far-infrared radiation (10960 cm-1): Dominant for coolingbelow ~2.5×10-3 hPa.
• Infrared and solar radiation (9602000 cm-1): Dominant for coolingabove ~2.5×10-3 hPa, and verysmall effects below.
• Solar radiation in near-infrared andvisible (2000-11800 cm-1): Dominant
for heating, especially below~1×10-2 hPa. Absorption in visible(10800-11800 cm-1) is small (up to~5% of the total below ~100 hPa).

Results

Solid: Band
Dashed: Line-by-line

Heating/cooling rates(Profile 2)• The balance of heating/cooling is
the same as Profile 1.
• If the effect of solar radiation in
960-2000 cm-1 is turned off, thecooling in upper atmospherebecomes weaker in up to ~1 K/day.
(The effect of CH4 band in 12001400 cm-1 is dominant)Sensitivity of solar radiationin 900-2000 cm-1

Results

Solid: Band
Dashed: Line-by-line

Sensitivity of molecules(Profile 2)

About the effect of cooling in midand far-infrared (10-960 cm-1):• C2H2 is dominant above ~0.03
hPa (up to ~3 K/day).
• C2H6 is dominant between 0.0310 hPa (up to ~0.3 K/day in thisheight region).
• Collision-induced transitions are
dominant below ~10 hPa (up tp~0.02 K/day).
• The effect of CH4 is very small inthis wavelength region.

Summary (1/2)• Jupiter’s stratosphere may be a very interesting target in thestandpoint of atmospheric dynamics and beyond, and we aredeveloping a GCM for the investigations.
• Fast and effective calculations are needed for the GCM, and wehave developed a band radiative transfer model based on thecorrelated k-distribution approach (using the framework of‘mstrnX’, Sekiguchi and Nakajima [2008]).
• The band model can calculate the heating/cooling rates in a good
accuracy in comparison with the line-by-line calculations.
• The effects of CH4 in 1200-1400 cm-1 and C2H2 in 600-860 cm-1 aredominant for cooling in upper stratosphere (above ~10-2 hPa).
• The effect of C2H6 in 700-960 cm-1 is dominant for cooling in
middle stratosphere (between ~10-2 and ~101 hPa).
• The effect of collision-induced transitions is dominant for coolingin lower stratosphere (below ~101 hPa).

Summary (2/2)• Heating by solar absorption is made by CH4, making a goodheating/cooling balance below ~10-2 hPa.
• Most absorptions are made in near-infrared
wavelength, but absorptions in visible
wavelength may not be ignorable in lower
stratosphere (up to ~5% of the total).

Future works• Comparison of the results of calculated heat balances with apreceding study [Yelle et al., 2001]• Implementation of this band radiation code to German GCMs for
Jupiter’s/Saturn’s stratosphere• Setting on the dynamical studies of giant planets with the GCMs
• Observations by JUICE-SWI