Numerical Modeling of Moist Convection in Jovian Planets considering negative buoyancy due to large amount of heavy components

Abstract:

In the atmospheres of Jovian planets, it is possible that condensation of heavy components, such as H₂O, NH₃, CH₄, and formation of NH₄SH by chemical reaction of NH₃ and H₂S suppress vertical convection. The criteria of convection inhibition have been estimated based on thermodynamic consideration (Guillot, 1995; Nakajima et al, AGU Fall Meeting 2019). However, the details on the realization of such suppression have not been investigated using numerical fluid dynamical models yet. Here we examine the structure of convection in parameters where convection inhibition by H₂O condensation or NH₄SH formation is anticipated to emerge using a non-hydrostatic cloud convection model (Sugiyama et al 2009, 2011, 2014).

The results of our two-dimensional numerical experiments show that active moist convection occurs intermittently even in the case where all of the condensable components are 30 times solar. A prominent feature is that the intense convective activities are organized like "squall lines" in the earth's atmosphere. That is, evaporation of rain falling from the upper clouds drives downward flow, which is braked around the stable layer at the H₂O condensation level and deflected sideways to form a strong "cold air outflow". At the front of the outflow, intense horizontal convergence triggers new convective clouds overcoming the negative buoyancy due to the large H₂O mixing ratio. In this series of cloud developments, the statically stable H₂O condensation level acts like "ground surface" for the Earth's squall lines. Additionally, in some experiments considering inhibition of cloud convection associated with NH₄SH chemical formation, similar features are observed.