COMMAS

COMMAS is a three-dimensional, nonhydrostatic model which has been used extensively for high-resolution atmospheric convective and mesoscale applications. Numerical approximations include centered time and space approximations for the momentum equations and monotonic parabolic advection for scalar quantities. A time-split method is used in which sound wave terms are integrated using a small time step and gravity wave, advection, and turbulence terms on a large time step in order to reduce computer time and maintain numerical stability. Further, the model incorporates a vertically stretched grid and multiple two-way interactive grids with finer resolution can be embedded in coarser resolution grids. Microphysics is handled using the Kessler parameterizations. Open and periodic lateral boundary conditions are supported.

The COMMAS model was developed by Louis Wicker and Robert Wilhelmson at the University of Illinois (Wicker is now at Texas A&M). The interactive nesting capabilities were incorporated by William Skamarock (National Center for Atmospheric Research). COMMAS was developed on CRAY systems but is written in FORTRAN 77 and designed for quick portability to most UNIX systems. It has been tested on the Convex and the CRAY-2/Y-MP/C-90 supercomputers, SGI workstations and Power Challenge and Origin2000, and IBM RS-6000 and DEC Alpha workstations. Further information can be obtained from Robert Wilhelmson (email: bw@ncsa.uiuc.edu; homepage)

REFERENCES

Skamarock, W. C., J. Oliger, and R. L. Street, 1989:  Adaptive
    grid refinement for numerical weather prediction.  J. Comp.
    Phys., 80, 27-60.

Wicker, L. J., 1990:  A numerical simulation of a tornado-scale
    vortex in a three-dimensional cloud model.  Ph. D.
    dissertation, University of Illinois Department of Atmospheric
    Sciences, Urbana, IL 61801, 264 pp.

Wicker, L. J., and R. B. Wilhelmson, 1990:  Numerical simulation
    of a tornado-like vortex in a high resolution three dimensional
    cloud model.  Preprints, 16th Conf. on Severe Local Storms,
    Kananaskis Park, Amer. Meteor. Soc., pp. 263-268.

Wicker, L. J., and R. B. Wilhelmson, 1995: Simulation and analysis of
    tornado development and decay within a three-dimensional supercell
    thunderstorm. J. Atmos Sci., 52, 2675-2703.