J/A+A/548/A90 Looking for the rainbow on exoplanets (Karalidi+, 2012)
Looking for the rainbow on exoplanets covered by liquid and icy water clouds.
Karalidi T., Stam D.M., Hovenier J.W.
<Astron. Astrophys. 548, A90 (2012)>
=2012A&A...548A..90K 2012A&A...548A..90K
ADC_Keywords: Models ; Planets ; Polarization
Keywords: methods: numerical - polarization -
planets and satellites: atmospheres - techniques: polarimetric
Abstract:
Looking for the primary rainbow in starlight that is reflected by
exoplanets appears to be a promising method to search for liquid water
clouds in exoplanetary atmospheres. Ice water clouds, that consist of
water crystals instead of water droplets, could potentially mask the
rainbow feature in the planetary signal by covering liquid water
clouds. Here, we investigate the strength of the rainbow feature for
exoplanets that have liquid and icy water clouds in their atmosphere,
and calculate the rainbow feature for a realistic cloud coverage of
Earth.
We calculate flux and polarization signals of starlight that is
reflected by horizontally and vertically inhomogeneous Earth-like
exoplanets, covered by patchy clouds consisting of liquid water
droplets or water ice crystals. The planetary surfaces are black.
Description:
Tables containing the data for reproduction of the Figures of the
paper. For simplicity the data for reproduction of every figure are
split in a separate file. The latter is named after the Figure it
reproduces. Every file contains a 7 line header briefly describing the
figure it reproduces.
At large phase angles while the flux appears to be zero, in some cases
the polarization is non-zero. This is due to numerical effects related
to the print-out format we use.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig5.dat 54 1001 Planet with various cloud coverages at 550nm
fig7.dat 54 360 Planet with various cloud coverages at 865nm
fig8.dat 215 91 Planet with two cloud layers of liquid water
with various optical thicknesses at 550nm (G2)
fig9.dat 40 540 Planet with two cloud layers, top layer icy cloud
of variable optical thickness
fig10.dat 54 270 Planet with two cloud layers, top layer icy cloud
of thickness b=2 at various wavelengths
fig11.dat 40 360 Planet with two cloud layers (top layer ice);
the top layer covers a variable percentage of the
underlying liquid water clouds
fig12.dat 40 270 Planet with two cloud layers (top layer ice);
the top layer covers 40% of the underlying liquid
water clouds at various wavelengths
fig14.dat 40 180 Model planet with 2 cloud layers: an ice water
cloud and a liquid water cloud layer; based on
data from MODIS/Aqua database.
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Byte-by-byte Description of file (#): fig5.dat fig7.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 % Cov [0/100] Cloud coverage
8- 12 F5.1 deg phi [0/180] Phase angle α (G1)
17- 26 F10.8 --- pi*Fn Reflected total flux, π*Fn
31- 40 F10.8 --- pi*Fnp Polarized flux, π*Fn,p
45- 54 F10.8 --- P Degree of polarization
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Byte-by-byte Description of file (#): fig8.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 deg phi [0/180] Phase angle α (G1)
9- 19 F11.8 --- pi*Fn(10,1) Reflected flux for bB=10, bA=1 (G2)
24- 33 F10.8 --- pi*Fnp(10,1) Polarized flux for bB=10, bA=1 (G2)
37- 47 F11.8 --- P(10,1) Polarization degree for bB=10, bA=1 (G2)
51- 61 F11.8 --- pi*Fn(2,1) Reflected flux for bB=2, bA=1 (G2)
66- 75 F10.8 --- pi*Fnp(2,1) Polarized flux for bB=2, bA=1 (G2)
79- 89 F11.8 --- P(2,1) Polarization degree for bB=2, bA=1 (G2)
93-103 F11.8 --- pi*Fn(0,1) Reflected flux for bB=0, bA=1 (G2)
108-117 F10.8 --- pi*Fnp(0,1) Polarized flux for bB=0, bA=1 (G2)
121-131 F11.8 --- P(0,1) Polarization degree for bB=0, bA=1 (G2)
135-145 F11.8 --- pi*Fn(10,0) Reflected flux for bB=10, bA=0 (G2)
150-159 F10.8 --- pi*Fnp(10,0) Polarized flux for bB=10, bA=0 (G2)
163-173 F11.8 --- P(10,0) Polarization degree for bB=10, bA=0 (G2)
177-187 F11.8 --- pi*Fn(2,0) Reflected flux for bB=2, bA=0 (G2)
192-201 F10.8 --- pi*Fnp(2,0) Polarized flux for bB=2, bA=0 (G2)
205-215 F11.8 --- P(2,0) Polarization degree for bB=2, bA=0 (G2)
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Byte-by-byte Description of file (#): fig9.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 nm lambda Wavelength λ
8- 12 F5.1 deg phi [0/180] Phase angle α (G1)
17- 26 F10.8 --- pi*Fn Reflected total flux, π*Fn
30- 40 F11.8 --- P Degree of polarization
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Byte-by-byte Description of file (#): fig10.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 --- b Ice cloud optical thickness
8- 12 F5.1 deg phi [0/180] Phase angle α (G1)
17- 26 F10.8 --- pi*Fn Reflected total flux, π*Fn
31- 40 F10.8 --- pi*Fnp Polarized flux, π*Fn,p
45- 54 F10.8 --- P Degree of polarization
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Byte-by-byte Description of file (#): fig11.dat
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Bytes Format Units Label Explanations
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2- 5 F4.1 % Cov [0/100] Cloud coverage
8- 12 F5.1 deg phi [0/180] Phase angle α (G1)
17- 26 F10.8 --- pi*Fn Reflected total flux, π*Fn
31- 40 F10.8 --- P Degree of polarization
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Byte-by-byte Description of file (#): fig12.dat fig14.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 nm lambda Wavelength λ
8- 12 F5.1 deg phi [0/180] Phase angle α (G1)
16- 26 F11.8 --- pi*Fn Reflected total flux, π*Fn
30- 40 F11.8 --- P Degree of polarization
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Global Notes:
Note (G1): the phase angle α is the angle between the parent star and
the observer as seen from the center of the planet
Note (G2): computations of reflected total flux (πFn) and polarized
flux (πFn,p) and polarization degree (P) for a planet having a
lower coverage of 42.3 of type B liquid water clouds, and an upper
coverage of 16% of type A liquid water cloud, for various values of
the cloud optical thicknesses bB and bA. The 2 types of liquid
water droplets have the characteristics:
* type A: reff=0.1µm, effective variance 0.1;
* type B: reff=6.0µm, effective variance 0.4
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Acknowledgements:
Theodora Karalidi, androm3da1(at)gmail.com,
SRON Netherlands Institute for Space Research
(End) Patricia Vannier [CDS] 17-Jan-2013