Study of the Venus' upper haze

The Solar Occultation in the InfraRed (SOIR) onboard Venus Express (ESA) is designed to measure the atmospheric transmission at high altitudes (65–165 km) in the IR (2.2–4.3 μm) with high resolution by solar occultation. The SOIR data obtained in 2006-2009 are analyzed to examine the upper haze at altitude above 90 km. Vertical and latitudinal distribution of haze extinction, optical thickness and mixing ratio were calculated using statistics of the SOIR data. Extinctions and optical thickness due to aerosols at low latitude are two times thicker than those at high latitude. One of the notable results is the mixing ratio of aerosols increases at altitude above 90 km at both high and low latitudes. It is speculated that sources of haze are transported upward from altitude under 90 km and haze is produced at high altitude. From comparison with the vertical distributions of SO and SO2 mixing ratios reported by Belyaev et al. (2012), it is speculated about the correlation between sulfur oxides and haze.