[P-PS05] Science of Venus: knowing more about the earth's sister planet

[PPS05-P03] Study of SO₂ transport in Venus atmosphere using Akatsuki UV images and radiative transfer calculation

*Tatsuro Iwanaka¹, Takeshi Imamura¹ (1.Graduate School of Science, The University of Tokyo)

Keywords:Venus, atmosphere, radiative transfer

The distribution of H₂SO₄ clouds in the Venus atmosphere is an important factor that influences the solar energy absorbed by Venus. Understanding how SO₂, the precursor of cloud, is transported from the lower layers to the cloud top where the cloud is formed from SO₂ photochemically is essential for understanding the climate system of Venus. SO₂ is a major absorber in the near-UV region, and to observe the spatial distribution of SO₂, Akatsuki UVI takes UV images from the orbit around Venus. The 283- nm UV images taken by Akatsuki are thought to reflect the amount of SO₂ as an absorber, but they also include the effects of scattering by H₂SO₄ aerosols and CO₂, the main component of the atmosphere. That makes quantitative discussions difficult.
In this study, we developed a new method to estimate the SO₂ mixing ratio at the cloud top using a newly developed radiative transfer code from UV images taken by UVI under various conditions and estimated the SO₂ mixing ratio during the period from 2016 to 2020. We compared the local time-latitude distribution of the SO₂ mixing ratio with the atmospheric general circulation model by Takagi et al. (2018), and the dependence of the SO₂ mixing ratio to local time was consistent with that of the vertical wind and vertical movement of air calculated by the GCM.
In addition, we compared the vertical displacement of air estimated from the variation of the SO₂ mixing ratio with that calculated by the GCM. The results show that the SO₂ variations and the vertical air movements caused by the thermal tidal waves are on the same scale.
In this presentation, we will report these progresses.