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| Titel |
Study of Venus cloud layers with polarimetric data from SPICAV/VEx |
| VerfasserIn |
Loic Rossi, Emmanuel Marcq, Franck Montmessin, Jean-Loup Bertaux, Anna Fedorova, Daphne Stam |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092041
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| Publikation (Nr.) |
 EGU/EGU2014-6367.pdf |
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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. 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
effective radius of 0.23 ± 0.04μm, with a normalized size distribution variance of
0.18 ± 0.1.
We introduce here new polarimetric measurements from the SPICAV-IR spectrometer
onboard ESA’s Venus Express. Observing Venus in the visible and IR from 650nm to
1625nm with a good spatial and temporal converage, SPICAV gives us an opportunity to put
better constraints on haze and cloud particles at Venus cloud top, as well as their spatial and
temporal variability.
Our analysis is based on a polarized radiative transfer code similar to the one used by
Hansen and Hovenier (1974). Using the particle size distribution from Kawabata et al.(1980)
and a simple two-layered cloud model, we try to retrieve particle size and refrative index from
nadir observations. We are interested in particular by the glory which is also visible in
polarization and whose linear degree of polarization as a function of observation geometry is
dependent on the cloud parameters. The polarization measured at higher latitudes provides
constrains on the hazes, in particular their optical thickness. We will discuss the first results of
our modeling of the glory.
In the future we aim to characterize the cloud droplets on the planet along with their
temporal and spatial variability. A comparison with the photometric observations of the glory
from VMC could also provide stronger constrains on the size and composition of the cloud
particles.
References:
HANSEN, J.E. AND HOVENIER, J.W., Interpretation of the polarization of
Venus., Journal of Atmospheric Sciences, 1974.
KAWABATA et al., Cloud and haze properties from Pioneer Venus Polarimetry,
Journal of Geophysical Research, 1980 |
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