MC2 Model description

Draft document ... under development!

Dynamics

MC2 is a semi-implicit, semi-lagrangian discretization of the Euler (compressible) equations. Thus it is a non-hydrostatic model. Originally designed bby the late (1993) Prof. André Robert (Tanguay et al., 1990); it is described in Benoit et al., 1997. It is a Limited Area Model (LAM). MC2 stands for "Mesoscale Compressible Community" (model).

Clean open boundaries (Thomas, Girard et al.).
Explicit handling of convection (semi-lagrangian hydrometeors of the KY scheme)

Handling of the terrain

DEM (200 meter for Swiss, ~1 km for rest) averaged to model mesh and then filtered to remove 3 delta x features

Sponge Layer

Diffusive (del^2) sponge below lid; not Rayleigh damping

Physics

• Radiation : IR Garand (1983, Garand et Mailhot 1990); Solar: Fouquart-Bonnel
  (1980)
• Surface boundary layer : Force-restore method (Deardorff 1978; Benoit et al
  1989)
• Turbulence and Vertical diffusion :Turbulent Kinetic Energy (Benoit et al 1989)
• Horizontal diffusion : Fourth order (KH *del^4)
• Orography treatment : Filtered over 3 grid points
• Subgrid scale orography : Effective Z0 computed following Georgelin (1994)
• Gravity wave drag: none
• Convective parameterization: none. Handled explicitly.
• Condensation and cloud processes. Two-phase, dual ice scheme of Kong and Yau (1997).

Computational aspects

A massively parallel message-passing implementation of the model has been developed at RPN based on the MSG toolkit developed for the P_SPARSLIB library of parallel iterative solvers (Thomas et al. 1997, 1998). The MC2 can use a domain-decomposition as well as a multi-tasking approac (or a combination of the two), to solve a given forecast 3D grid.

Bibliography

Benoit, R., M. Desgagne, P. Pellerin, S. Pellerin, Y. Chartier and S. Desjardins, 1997:
The canadian MC2: A semi-lagrangian, semi-implicit wide-band atmospheric model
suited for fine-scale process studies and simulation. Mon. Wea. Rev., Vol 125. MC2_meso_MWR97.pdf (3.5MB)

Benoit, R., J. Cote and J. Mailhot, 1989: Inclusion of a TKE boundary layer
parameterization in the Canadian regional finit-element model. Mon. Wea. Rev., 117,
1726-1750.

Deardorff, J.W., 1976: Efficient prediction of grounds surface temperature and moisture
with inclusion of a layer of vegetation. J.Geophy. Res., 83, 1889-1903.

Fouquart, Y. and B. Bonnel, 1980: Computation of solar heating of the eart's
atmosphere: a new parameterisation. Contrib. Atmos. Phys., 53, 35-63.

Garand, L., 1983: Some improvement and complements of the infrared emissivity
algorithm including a parameterization of the absorption in the continuum region. J.
Atmos. Sci., 40, 230-244.

Garand, L. and J. Mailhot, 1990: The influence of the infrared radiation on numerical
weather forecasts. Proceedings of the Seventh Conference on Atmospheric
Radiation, 23-27 July 1990, San Francisco, U.S.A., Amer. Meteor. Soc., J146-J151.

Georgelin, M., E. Richard, M. Petitdidier and A. Druilhet, 1994: Impact of subgrid-scale
orography parameterization on the simulation of orographic flows. Mon. Wea. Rev., 122,
1509-1522.

Kong, F. and M. K. Yau, 1997: An Explicit Approach of Microphysics in MC2. Atmosphere-Ocean, 35, 257-291.

Laprise, R., C. Caya, G. Bergeron and M. Giguère, 1997: The formulation of the André Robert MC2 (Mesoscale Compressible Community) Model. Atmosphere Ocean, 35, 195-220

Pinty, J.-P., R. Benoit, E. Richard and R. Laprise, 1995: Simple tests of a semi-implicit semi-Lagrangian model on 2D mountain wave problems. Mon. Wea. Rev., 123, 3042-3058.

Tanguay, M., A. Robert and R. Laprise, 1990: A semi-implicit semi-lagrangian fully compressible regional forecast model. Mon. Wea. Rev., 118, 1970-1980

Thomas, S. J., C. Girard, R. Benoit, M. Desgagné, and P. Pellerin, 1998a: A new adiabatic kernel for the MC2 model. Atmosphere-Ocean, 36, 241-270.

Thomas, S. J., A. V. Malevsky, M. Desgagné, R. Benoit, P. Pellerin, and M. Valin, 1998b: Massively parallel implementation of the mesoscale compressible community model. Parallel Computing, 23, 2143-2160.

Thomas, S. J., M. Desgagné and M. Valin, 1999: High-resolution weather forecasting: a Teraflop sustained on RISC/CACHE or vector processors. High-Performance Computing Symposium 1999, Kingston, Canada. This conference. http://www.queensu.ca/hpcs99.