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| Titel |
Study of Venus' cloud layers by polarimetry using SPICAV/VEx |
| VerfasserIn |
Loic Rossi, Emmanuel Marcq, Franck Montmessin, Jean-Loup Bertaux, Oleg Korablev, Anna Fedorova |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074459
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| Zusammenfassung |
| The study of Venus’s cloud layers is important in order to understand the structure, radiative
balance and dynamics of the Venusian atmosphere. The main cloud layers between 50 and
70km are thought to consist in ~ 1μm radius droplets of a H2SO4-H2O solution.
Nevertheless, the composition and the size distribution of the droplets are difficult to
constrain more precisely. The polarization measurements have given great results in the
determination of the constituents of the haze. In the early 1980s, Kawabata et al.(1980) used
the polarization data from the OCPP instrument on the spacecraft Pioneer Venus to constrain
the properties of the haze. They obtained a refractive index of 1.45 ± 0.04 at λ = 550nm and
an effective radius of 0.23 ± 0.04μm, with a normalized size distribution variance of
0.18 ± 0.1.
Our work aims to reproduce the method used by Kawabata et al. by writing a
Lorentz-Mie scattering model and apply it to the so far unexploited polarization data of the
SPICAV-IR instrument on-board ESA’s Venus Express in order to better constrain haze and
cloud particles at the top of Venus’s clouds, as well as their spatial and temporal
variability.
We introduce here the model we developed, based on the BH-MIE scattering model.
Taking into account the same size distribution of droplets as Kawabata et al., we
obtained the polarization degree after a single Mie scattering by a haze at all phase
angles given the effective radius and variance of the distribution and the refractive
index of the droplets. Our model seems consistent as it reproduces the polarization
degree modeled by Kawabata et al. We also present the first application of our
model to the SPICAV-IR data under the single scattering assumption. Hence we can
confirm the mean constraints on the size and refractive index of the haze and cloud
droplets.
In the near future, we then aim to extend our study of the polarization data by integrating
our model into a radiative transfer model which will take into account the multiple scattering.
Having more recent observations in wavelengths ranging from 650 to 1625nm, will put
better constraints on the properties of both cloud and haze particles, with a primary focus on
the cloud droplets characterization.
Bibliography:
BOHREN, C. F. AND HUMAN, D.R., in Absorption and Scattering of light by
small particles, Wiley, 1983
KAWABATA, K. et al., Cloud and haze properties from Pioneer Venus
Polarimetry, JGR, 1980 |
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