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Addition of moist convective parameterization to the EPIC model

Presentation #103.02D in the session “Giant Planets 2: Simulation and Lab Work”.

Published onOct 26, 2020
Addition of moist convective parameterization to the EPIC model

Cloud features observed on Gas Giants are highly dynamic and form in a myriad of shapes and colors. The interplay between different condensing species that form these clouds have been studied in detail and are understood to be driven by dynamical processes in the deep atmosphere. Due to the upper level clouds, direct observation of the composition and dynamics at depth is difficult, and thus, it is necessary to use computer simulations to infer these properties. One such method is using the Explicit Planetary Isentropic Coordinate (EPIC) General Circulation Model (GCM), which solves the Navier-Stokes equations on an oblate spheroid with a hydrostatic approximation and contains an active bulk microphysics module to simulate cloud processes. We have now updated the model to account for a sub-grid scale moist convective parameterization using the Relaxed Arakawa-Schubert (RAS) scheme detailed by Moorthi and Suarez (1992), so as to be able to model convective plumes with origins in the deep troposphere. This scheme describes the changes in vertical temperature and condensible loading (i.e. the vertical sounding) in a column of atmosphere (a grid-cell) by invoking cumulus cloud formation several times within a timestep based on the available potential energy for convection. A relaxation parameter is applied to the sounding update to reduce spurious cloud growth, leading to a numerically stable and computationally efficient updraft model, which can be applied to a hydrostatic GCM. Here, we present the addition of the RAS scheme to the EPIC model and show the effect of cumulus water cloud formation on the upper tropospheric ammonia clouds. The deep water clouds, when perturbed, reach the base of the ammonia clouds, which are consequently morphed by the upwelling plume. We also present preliminary results of the RAS scheme applied to the 24 degree N jet, where lightning and convective upwelling events have been observed.

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