Parallel I/O for 3-D Global FDTD Earth–Ionosphere Waveguide Models at Resolutions on the Order of ~1 km and Higher Using HDF5

3-D finite-difference time-domain (FDTD) models of the global Earth–ionosphere waveguide have reached grid resolutions on the order of $1\times 1 \times 1$ km and higher. At these high resolutions, efficient parallel input–output (I/O) schemes are required to keep the simulation run times reasonable. However, generating optimal parallel I/O schemes is challenging due to the spherical-coordinate global mesh that includes merging of cells in the east–west direction as either pole is approached. Hierarchical Data Format 5 (HDF5) is applied and optimized for a global latitude–longitude FDTD model. The performance of the parallel HDF5 approach is compared with a message passing interface-based approach and a brute-force approach. The methodology presented here may be simplified to Cartesian-based grids in a straightforward manner.