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This study uses the PyMieDAP radiative transfer model to simulate the radiative properties of Venus' clouds and haze, investigating how their microphysical characteristics affect linear polarization, in comparison with near-infrared polarization data from the SPICAV IR instrument aboard Venus Express. The results show that single-scattered fluxes of the four particle modes decrease in the phase angle range of 0° to 120°, but increase near 160°. Mode 1 particles (upper haze) exhibit Rayleigh scattering characteristics, with polarization transitioning from positive to negative as the wavelength increases. Mode 2 and Mode 2' particles display two positive polarization peaks near 15° and 160°, with polarization reversing in the near-infrared. Mode 3 particles show oscillations in polarization near 105°, flipping from positive to negative between 155° and 165°. The primary polarization peak occurs near 15°, corresponding to the main rainbow, while a secondary peak between 150° and 160° is attributed to anomalous diffraction.
The microphysical properties of upper clouds and haze (Mode 1 and Mode 2) significantly affect Venus' linear polarization, while those of lower clouds (Mode 2' and Mode 3) have a minimal impact. A reduction in Mode 1 column density increases the polarization peak at the main rainbow, while an increase in Mode 2 column density has the opposite effect. Changes in modal radius enhance polarization peaks for Mode 1 and Mode 2, while increasing geometric standard deviation reduces polarization peaks and shifts their phase angles. The real part of the complex refractive index has a greater impact on polarization than the imaginary part. Simulations using the multilayer model show better agreement with SPICAV IR data, consistent with the larger particle sizes in Venus' haze.The integrated linear polarization across the Venus disk varies with wavelength and phase angle, with higher polarization at the disk's edge. Variations in cloud coverage also influence polarization, with less cloudy regions exhibiting higher values. Future studies should explore the effects of cloud and haze parameters on line polarization, as inversion of these parameters is beyond the scope of this work.-
Keywords:
- Venusian clouds and haze /
- linear polarization /
- sensitivity analysis /
- microphysical properties
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