1/25 deg Atlantic Ocean Simulation Using HYCOM
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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Traditional ocean models use a single coordinate type to represent the vertical, but no single approach is optimal for the global ocean. Isopycnal density tracking layers are best in the deep stratified ocean, z-levels constant fixed depths provide high vertical resolution in the mixed layer, and -levels terrain-following are often the best choice in coastal regions. The HYbrid Coordinate Ocean Model HYCOM combines all three approaches by dynamically choosing the optimal distribution at every time step via the layered continuity equation. This has lead to HYCOM being chosen for the next generation of ocean prediction systems both by NAVOCEANO and by NOAA. HYCOMs basic parallelization strategy is 2-D domain decomposition, i.e., the region is divided up into smaller sub-domains, or tiles, and each processor owns one tile. Tiles that are entirely over land are discarded. A halo is added around each tile to allow communication operations e.g., updating the halo to be completely separated from computational kernels, greatly increasing the maintainability and expendability of the code base. Rather than the conventional 1 or 2 element wide halo, HYCOM has a 6 element wide halo is consumed over several operations to reduce halo communication overhead. The communication mechanism implementing domain decomposition can be either MPI or Crays SHMEM library.
- Physical and Dynamic Oceanography