Investigation of the unknown UV absorber(s) in the atmosphere of Venus using a chemistry-transport model in combination with a radiative transfer model

Abstract:

Ever since the detection of the enigmatic ultraviolet (UV) absorption in the upper atmosphere of Venus, questions have been raised about the identity of the unknown UV-visible absorber(s) and how it is formed on Venus. Our recent photochemical modeling study suggests that S₂O, higher order polysulfur oxide, S_nO, species and polysulfur, S_n, which are generated from reactions of the SO dimers in Venus’s atmosphere, are possible candidates for the UV-visible absorber(s). Comprehensive gas-phase chemistry [Zhang et al. 2012] with updates was included in the 1-D diurnally and photochemical model. Calculated SO₂ and SO profiles agree reasonably well with observations throughout the mesosphere, including the upper mesosphere inversion layer. Unlike previous studies, no fixed source of upper mesosphere sulfur was prescribed. Calculated SO dimer abundances peaked at ~ 0.1 parts per billion (ppb) at about 65 km altitude. Gas phase S_n and S_nO abundances also peaked near 65 km at ~ 0.1 ppb. In an extension of this study, we make the first attempt to combine a chemistry-transport model with a radiative transfer model to investigate the absorption features of the important sulfur species in the upper atmosphere of Venus. Our modeling results will be compared to existing observations, which can provide useful constraints for unraveling the identity(ies) of the unknown UV-visible absorber(s) on Venus.