Latitude-Longitude Grid
Most grid point atmospheric models (and almost all ocean models) are
discretized on a latitude-longitude grid (shown above). The meridians
(great arcs that join the poles) converge so that the zonal separation
becomes very small near the poles (shown in close-up below).
For the grid shown above, the zonal grid spacing scales with the
number of points around the equator to the power of two; doubling the
equatorial resolution quarters the zonal spacing in the last latitude
circle around the poles.