Op:halo_extend

duo duofinite_volume arc_lengthbasis_coscorner_fillcrossflux_divergencehalo_extendkinetic_energymetricmomentum_umomentum_vpgrad_direct_upgrad_direct_vpgrad_l97_upgrad_l97_vreconstructriemannspherical_angletangentupwindwavespeedwind_assywind_rotatewind_solve duo
Generic gnomonic cubed-sphere grid with the duo-grid halo system of Chen (2021): six N-by-N tiles interlocked in the 'staircase' arrangement, 6 N^2 cells, unstaggered (A-grid) so every prognostic variable is collocated at cell centres.