Three-Dimensional Venus Cloud Structure Simulated by a General Circulation Model

doi:10.1029/2023JE008088

Three-Dimensional Venus Cloud Structure Simulated by a General Circulation Model

2024-07-24

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DOI：10.1029/2023JE008088

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The clouds have a great impact on Venus's energy budget and climate evolution, but its three-dimensional structure is still not well understood. Here we incorporate a simple Venus cloud physics scheme into a flexible GCM to investigate the three-dimensional cloud spatial variability. Our simulations show good agreement with observations in terms of the vertical profiles of clouds and H2SO4 vapor. H2O vapor is overestimated above the clouds due to efficient transport in the cloud region. The cloud top decreases as latitude increases, qualitatively consistent with Venus Express observations. The underlying mechanism is the combination of H2SO4 chemical production and meridional circulation. The mixing ratios of H2SO4 at 50-60 km and H2O vapors in the main cloud deck basically exhibit maxima around the equator, due to the effect of temperature's control on the saturation vapor mixing ratios of the two species. The cloud mass distribution is subject to both H2SO4 chemical production and dynamical transport and shows a pattern that peaks around the equator in the upper cloud while peaks at mid-high latitudes in the middle cloud. At low latitudes, H2SO4 and H2O vapors, cloud mass loading and acidity show semidiurnal variations at different altitude ranges, which can be validated against future missions. Our model emphasizes the complexity of the Venus climate system and the great need for more observations and simulations to unravel its spatial variability and underlying atmospheric and/or geological processes. On Venus, highly reflective clouds cover the surface entirely. This means that the clouds greatly impact Venus's current and, very likely, past energy budget. Therefore, understanding the Venus clouds is essential to constructing a full paradigm of the Venus climate and evolution. However, due to the lack of both three-dimensional, long-term observations and comprehensive climate models, the cloud spatial structure and its impact on atmospheric processes remain elusive. Here, we construct a three-dimensional climate model that includes cloud physics and simple chemistry as the first step toward fully understanding the Venus clouds. Our simulated vertical profiles of the Venus clouds agree well with observations. We find that the condensable gases, sulfuric acid and water vapors in the cloud region become more abundant in the lower latitudes due to the temperature difference over different latitudes. The cloud top becomes lower as it approaches the polar region, and the underpinning processes are related to sulfuric acid chemical production and meridional circulation. The equatorial cloud structure shows semidiurnal features, which are related to the excited thermal tides in the Venus atmosphere. Our study is preparing for future Venus missions like EnVision, to maximize their science returns. We construct a Venus climate model with cloud physics, and the cloud vertical structure agrees with observations H2SO4 and H2O vapors in the middle cloud basically follow their SVMRs and show higher concentrations at low latitudes The semidiurnal thermal tide affects H2SO4 and H2O vapors, cloud mass loading and acidity at different altitudes

Keyword:

Venus

atmospheric dynamics

cloud physics

general-circulation model

Three-Dimensional Venus Cloud Structure Simulated by a General Circulation Model

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