WRF and ROMS are coupled using the Model Coupling Toolkit (MCT) developed at Argonne National Laboratory. MCT is a Fortran90 library built on top of MPI with data types and methods that simplify the construction of distributed-memory parallel couplers. The coupler design itself is parallel, avoiding bottlenecks by allowing for parallel exchange of fields between models on different grids, and time averaging over the coupling period. The coupling is wired into the mediation layer in WRF, and into the I/O layer in ROMS.

The coupling passes wind-stress, heat, shortwave radiation and evaporation/precipitation from WRF to ROMS and sea surface temperature from ROMS to WRF. Simulations run include supercell simulations, hurricane vortex generation, and general circulation studies of the northeast Pacific and Gulf of Alaska.

An API was developed that allows coupling and I/O using MCT and HDF5, and utilizing this API in both WRF and ROMS coupling runs across a TeraGrid using MPICH-G2 are shown.