A 3-DIMENSIONAL NUMERICAL-MODEL OF CLOUD DYNAMICS, MICROPHYSICS, AND CHEMISTRY .1. CONCEPTS AND FORMULATION

We have developed a three-dimensional, comprehensive cloud modeling system with detailed descriptions of dynamics, microphysics, and chemistry. This system can be used to study not only the evolution of dynamical and microphysical processes, but also those of chemical processes and the interactions or relationships among them. The primary objective of this model is the simulation of deep convective events and severe storms, although in principle the stratiform clouds and clouds in frontal systems could also be included with some improvements of the model. The physical component of this model starts with a pseudo-elastic form of the continuity equation. The overall model is a self-consistent, time-dependent system which is easier to solve. A so-called ice-liquid potential temperature is used as a thermodynamic conservative variable. Seven different Water categories in three phases am considered in this model. Both the mass mixing ratio and concentration of each liquid or solid phase category are predicted so that a semi-spectra microphysical parameterization scheme can be formulated. More than 40 microphysical processes have been parameterized based on the spectrum-integration and the behavior of the individual particles in the microphysical interactions. Concentrations of seven chemical groups in air and in six liquid- or solid-phase water carriers are predicted by our chemical model. Their evolution in this model came from not only the dynamical and subgrid-scale transports, but also the chemical reactions and microphysics-related conversions. Modeling results include the dynamical features and appropriate detailed descriptions of microphysical and chemical evolution of the modeled clouds. This allows more direct comparison between model results and observational data. A potential use of this model would be in the analysis and interpretation of field observations.