Microphysical processes and dynamics of a jovian thundercloud

An axisymmetric time-dependent cloud model with dynamics and detailed microphysics of Jupiter’s water cumulus clouds is presented. The microphysical processes operating in these clouds are analyzed and compared to those of terrestrial clouds. Diffusional growth and coagulation of water drops and ice crystals were found to be faster and more efficient in Jupiter. Large particles were formed on short time scales and kept suspended by the strong updraft in the core of the developing cloud, which allowed them to grow by coalescence as they ascended to the upper regions of the cloud. Thus, clouds retained high values of mass mixing ratio (10 g kg⁻¹) and high concentrations of large particles (D > 100 μm). An evaluation of the minimum cloud condensation nuclei (CCN) and ice nuclei (IN) concentrations in Jupiter’s troposphere showed that for convective clouds to develop a vertical dimension of 45-50 km, CCN concentrations should be of the order of 100 cm⁻³; much lower concentrations resulted in relatively shallow clouds (10 km) and lower mass contents. The formation of ice by freezing or nucleation was found to contribute significantly to cloud development, due to the release of latent heat which counteracted the negative buoyancy created by the condensed mass. The required IN concentration was of the order of 0.1 cm⁻³.