Latitudinal and temporal variability of Venus clouds and hazes observed by polarimetry with SPICAV-IR

Abstract : The study of Venus’ cloud layers is important in order to understand the structure, radiative balance and dynamics of the Venusian atmosphere. Polarization measurements have given important constraints for the determination of the constituents of the clouds and haze. From ground based observations Hansen and Hovenier[1], using a ra- diative transfer model including polarization, found that the main cloud layers between 50 and 70 km consist of r ≃ 1 μm radius spherical droplets of a H2SO4 -H2O solution. In the early 1980s, Kawabata[2] used the polar- ization data from the OCPP instrument on the spacecraft Pioneer Venus to constrain the properties of the overly- ing haze. They found that the haze layer is composed of smaller particles with r ≃ 0.25 μm and similar re- fractive indices. Our work reproduces the method used by Hansen and Kawabata[1, 2]. We applied a radia- tive transfer model with polarization on the data of the SPICAV-IR instrument on-board ESA’s Venus Express. Our aim is to better constrain haze and cloud particles at the top of Venus’s clouds, as well as their spatial and temporal variability.