| Development of a Cloud Convection Model for Jupiter's Atmosphere | << Prev | Index| Next >> |
We developed a two-dimensional cloud convection model based on the quasi-compressible system [1] for the Jupiter's atmosphere that incorporates the condensation of H2O and NH3 and the production reaction of NH4SH. As a test run of the developed model, we performed a long-time numerical simulation of cloud convection where the cooling rate is set to be - 1 K/day, which is about 100 times larger than that appropriate for Jupiter's atmosphere, in order to reduce CPU time required to establish a statistical equilibrium state. A visualization technique, "RGB composite", is proposed in order to examine both the vertical structure of three-composition clouds and the characteristics of convective motion.
The visualization technique, "RGB composite", was very efficient in examining the structure of three-composition cloud convection (see Section 3.2). The vertical cloud profiles established in the test run is distinctly different from the classical three-layer structure that has been predicted by previous studies employing one-dimensional thermodynamic equilibrium model [3], [4] (see Fig. 1.1). H2O and NH4SH cloud particles, which condense in the lower atmosphere, are advected upward to the altitudes above the NH3 condensation level, and cloud particles of all three species coexist between the NH3 condensation level and the tropopause. This is caused by the weak stability of the stable layers associated with NH3 condensation and NH4SH production reaction, which allows the strong updrafts to ascend from the H2O condensation level to the tropopause. However, it should be emphasized that those results may quite possibly be due to the unrealistically large strength of the given radiative forcing. If a realistic strength of radiative forcing of the Jupiter's atmosphere were adopted, convective motion would likely be less vigorous and may permit the NH3 condensation level or NH4SH production level to act as distinct dynamical and compositional boundaries.
In order to consider the actual state of Jupiter”Ēs atmosphere, we are going to perform simulations adopting smaller realistic values for the radiative forcing in the upper troposphere and wider horizontal sizes for the computational domain. We also need to perform simulations with the key parameters of cloud microphysics varied over a wide range in order to recognize uncertainty of numerical results caused by the uncertainty of the cloud microphysical process for which, at the moment, the parameter values of the Earth's atmosphere is employed. On the bases of these efforts, we will perform simulations with the abundances of condensible volatiles having values varied over the range estimated in the theory of solar system formation and will attempt to modify the model from a two-dimensional model to a three-dimensional one for the purpose of understanding the variety of structures of cloud convection that can be established in Jupiter's atmosphere,
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