Parallel algorithms for semi-Lagrangian transport in global atmospheric circulation models

Global atmospheric circulation models (GCM) typically have three primary algorithmic components: columnar physics, spectral transform, and semi-Lagrangian transport. In developing parallel implementations, these three components are equally important and can be examined somewhat independently. A two-dimensional horizontal data decomposition of the three-dimensional computational grid leaves all physics computations on processor, and the only efficiency issues arise in load balancing. A recently completed study by the authors of different approaches to parallelizing the spectral transform showed several viable algorithms. Preliminary results of an analogous study of algorithmic alternatives for parallel semi-Lagrangian transport are described here