Development of a microphysical model for the H2SO4 - H2O clouds on Venus

Anni Määttänen 1 Slimane Bekki 2 Franck Montmessin 1 Sébastien Lebonnois 3, 4
1 IMPEC - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
2 STRATO - LATMOS
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : Clouds on Venus are formed of sulfuric acid aerosols. The clouds are optically very thick in the visible, inhibiting visual observation of the surface. The clouds are organized in three quite distinct layers with differing properties in terms of particle size distributions and possibly composition. Some early observations hint to the existence of other species in the clouds, but recent missions have not been able to verify their composition. The lowest cloud layers are very dynamic and the reason for the bi- and trimodal size distributions could be partly explained by mixing and distinct altitudes of nucleation. However, the possibility of mixed phase clouds and different chemical compositions of the droplets have not yet been evaluated. Both the clouds of Venus and aerosols found in the Earth's stratosphere are composed of sulfuric acid droplets. On the Earth, the sulfur in the stratosphere originates from OCS, a long-lived sulfur species emitted at the surface and transported by the general circulation, and from volcanic eruptions that can inject material above the tropopause. It is thought that the water - sulfuric acid droplets form by binary homogeneous nucleation on both planets. However, the existence of condensation nuclei on Venus has not been ruled out. We use a model developed for the sulfuric acid aerosols and polar stratospheric clouds (PSCs) in the terrestrial stratosphere (Jumelet et al., 2009; Larsen et al., 2000). The model describes several key microphysical processes, including nucleation via a parameterization for two-component nucleation (Vehkamäki et al., 2002) of water and sulfuric acid. This parameterization is in principle quite applicable for the Venusian atmosphere, but we discovered that the lower limit of relative humidity is still too high considering the extremely dry Venusian atmosphere. We are extending the parameterization of (Vehkamäki et al., 2002) to lower relative humidity (see another abstract by Määttänen et al., this conference). In addition to formation of droplets via nucleation, the model includes their subsequent growth by condensation, evaporation of droplets, coagulation, and sedimentation.
Complete list of metadatas

https://hal.archives-ouvertes.fr/hal-00749231
Contributor : Catherine Cardon <>
Submitted on : Wednesday, November 7, 2012 - 8:45:37 AM
Last modification on : Thursday, July 25, 2019 - 4:34:10 PM

Identifiers

  • HAL Id : hal-00749231, version 1

Citation

Anni Määttänen, Slimane Bekki, Franck Montmessin, Sébastien Lebonnois. Development of a microphysical model for the H2SO4 - H2O clouds on Venus. EAC 2012, European Aerosol Conference, Sep 2012, Granada, Spain. ⟨hal-00749231⟩

Share

Metrics

Record views

627