FOAM 1.5 Component Models
PCCM3-UW is a combination of two model codes. The majority of the code is PCCM2, the parallel version of CCM2 developed under the CHAMMP program by scientists at NCAR, Oak Ridge National Lab and Argonne. Various physics routines where modified or replaced by FOAM developer Robert Jacob (while a graduate student at UW-Madison) so that the atmospheric physics is equivalent to CCM3. (Currently equal to CCM3.6). Note that PCCM3-UW does not include the Land Surface Model (LSM) which was introduced with CCM3.
For detailed description of the atmospheric physics/dynamics, see the description of CCM3.
OM3 was also developed under the CHAMMP program by John Anderson at the University of Wisconsin-Madison. OM3 is a finite-difference, z-coordinate ocean model very similar to the MOM of GFDL. Unlike MOM, OM3 was developed from scratch in C as a parallel program, contains a fully explicit, double time-split solver for the barotropic component, is on an A-grid, and has a free surface. In many ways it is more similar to POP.
See the documentation for MOM and POP regarding z-coordinate ocean models.
Land, Hydrology, and River Runoff:
The basic land model in FOAM is taken from the default land model of CCM2: the land surface is broken into 5 main vegetation types and temperature is calculated with a 4 layer diffusion model where the thermal properties and thickness depend on the vegetation type. The fixed hydrology of the CCM2 model has been replaced with a simple bucket model with a 15cm deep bucket. Evporation is a smooth function of the depth of water in the bucket. The prescribed snow cover of the CCM2 land model has also been replaced with a simple prognostic scheme. Top "soil" layer thermal and albedo properties are modified by the presence of snow.
The overflow from the bucket model is routed to the ocean using a parallel river transport model developed by Robert Jacob from a serial river model written by Mike Coe.
See the Description of CCM2, NCAR Technical Note TN-382+STR, for a description of the land.
Sea Ice: CSIM 2.2.6
The sea ice model uses the thermodynamics of NCAR's CSIM version 2.2.6. This model allows for an ice fraction with growth and melting in leads, snow cover, penetrating radiation with brine pockets and uses a Semtner 0 or 2-layer model for sea ice temperature. Sea ice dynamics is not included in FOAM's version..
The coupler is the bulk of the original code written for FOAM. To accommodate the different resolutions of the ocean and atmosphere models, the coupler uses an "overlap grid" obtained by laying the atmosphere grid on top of the ocean grid. The fluxes of heat, etc. are calculated by the coupler on each overlap grid cell using the corresponding atmosphere and ocean temperatures. The fluxes are then accumulated onto the appropriate grid for use by the ocean or atmosphere. The coupler also performs time accumulation of ocean-atmosphere fluxes and merges land and ocean fluxes for passing to the atmosphere.
Due to the nature of the problems we wish to study, flux corrections are not employed.