VVCM

VVCM is a three-dimensional anelastic model that has been developed using the vorticity equation, which has a completely different logical structure for dynamics from the models based on the momentum equation.

In this model, the prognostic variables of the model are the horizontal components of vorticity, potential temperature and mixing ratios of various phases of water at all heights, and the vertical component of vorticity and the horizontally uniform part of horizontal velocity at a selected height. With the use of an expression for the nondivergence of the vorticity vector, the vertical component of vorticity at the other heights is diagnostically determined. The non-uniform part of horizontal velocity at the selected height is obtained by solving the two-dimensional Poisson-type equations for streamfunction and velocity potential. The horizontal velocity at the other heights is then updated from the predicted vorticity fields and the velocity obtained at the selected height. For the vertical velocity, a three-dimensional elliptic equation is solved with prescribed vertical boundary conditions. This procedure replaces solving the elliptic equation for the perturbation pressure in the standard anelastic system based on the momentum equation. For advection of vorticity and scalar variables, the model uses a partially 3rd-order scheme. When time is continuous, this scheme is quadratically bounded.

The physical parameterizations in the model include a three-phase microphysical parameterization (Krueger et al., 1995; Lin et al., 1983; Lord et al., 1984), a radiative transfer parameterization (Fu et al., 1995), a surface flux parameterization (Deardorff, 1972), and a first-order turbulence closure that uses eddy viscosity and diffusivity coefficients depending on deformation and stability (Shutts and Gray, 1994).

Examples of Model Results

VVCM was developed by a team of researchers at Department of Atmospheric Science, Colorado State University and Department of Atmospheric and Oceanic Sciences, UCLA. If you need further information, please contact Dr. Joon-Hee Jung