Arakawa staggered grid

Grid family: arakawa
Kind: grid
Source: src/grids/arakawa.jl
Tags: #grid #staggered #arakawa #c-grid #b-grid #shallow-water

Description

The Arakawa family is not a standalone topology — it is a stagger wrapper around a base curvilinear grid (Cartesian or lat-lon). It assigns prognostic variables to one of four canonical locations per cell. The location enum (VarLocation, exported from the package) is CellCenter, UEdge, VEdge, Corner:

`VarLocation`	Accessor	Variable held there	Used by
`CellCenter`	`cell_centers(grid, i, j)`	scalars (mass `h`, pressure, tracers)	A, B, C, D, E
`UEdge`	`u_face(grid, i, j)`	u-component of velocity	C, D, E
`VEdge`	`v_face(grid, i, j)`	v-component of velocity	C, D, E
`Corner`	`corners(grid, i, j)`	u, v together (B)	B

The Arakawa A/B/C/D/E distinction is just the choice of which subset of locations carries u, v, and h (the per-stagger table lives in arakawa_variable_locations in src/grids/arakawa.jl):

A-grid (ArakawaA): all variables co-located at cell centers (simple but hosts checkerboard modes for the divergence operator)
B-grid (ArakawaB): h at center, both u and v at corners
C-grid (ArakawaC): h at center, u on the U-edge, v on the V-edge (good for wave equations and divergence-conservative discretizations)
D-grid (ArakawaD): dual of C — u and v swapped between the U-edge and V-edge
E-grid (ArakawaE): rotated arrangement with u and v on edges (the stagger parser accepts :E)

A grid is constructed via EarthSciDiscretizations.grids.arakawa(; base, stagger, ghosts, dtype), where stagger is one of :A, :B, :C, :D, :E and base is the underlying Cartesian or lat-lon grid.

ESD currently seeds the C-grid via the divergence_arakawa_c rule, which demonstrates the stagger_enum / requires_locations / emits_location fields used to make stagger-position selectors authoritative in the rule schema.

Visualization

Arakawa A/B/C/D stagger comparison — Variable placement on a single cell for each Arakawa stagger: A (all co-located), B (uv on vertices), C (u on face_x, v on face_y), D (the dual of C).

Trait coverage

Registered against AbstractStaggeredGrid (which sits beneath AbstractCurvilinearGrid). The base-grid trait calls all delegate to the underlying Cartesian / lat-lon implementation; stagger-aware accessors — cell_centers, u_face, v_face, corners — return the coordinate at the location where each prognostic variable lives for the chosen stagger.

Description

Visualization

Trait coverage

See also