Parallel Algorithms for Semi - Lagrangian Transport in GlobalAtmospheric Circulation

Global atmospheric circulation models (GCM) typically have three primary algorith-mic components: columnar physics, spectral tranform, 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 eeciency issues arise in load balancing. A recently completed study by the authors of diierent 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.