Some references on the sphere:

• Logically Rectangular Grids and Finite Volume Methods for PDEs in Circular and Spherical Domains,
  by Donna A. Calhoun, Christiane Helzel, and Randall J. LeVeque, SIAM Review 50 (2008), 723-752.

• Talk at BIRS, 2008

• Logically Rectangular Finite Volume Methods with Adaptive Refinement on the Sphere,
  by M. J. Berger and D. A. Calhoun, and C. Helzel, and R. J. LeVeque Phil. Trans. R. Soc. A 2009 367, 4483-4496. doi: 10.1098/rsta.2009.0168