Staggered grid. In the adopted finite-volume method, the horizontal axis is divided into M intervals and the vertical axis into N intervals, which represents M × N cells (here, M = 5 and N = 4). Horizontal levels are indexed by j and vertical levels by k. The left and right boundaries of the physical domain correspond to (sub-stellar point) and (anti-stellar point), respectively. The top and bottom boundaries correspond to σ = 0 (space) and σ = 1 (ground), respectively. The horizontal and vertical mass flows, V and W, are evaluated at vertical and horizontal cell interfaces, respectively, while the mass, temperature, geopotential, specific humidity, and Exner function (blue) are evaluated at cell centres. The physical domain is surrounded by ghost cells (grey), which are employed to facilitate vectorisation.