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5.6 Discretization     continued...

Figure 19: The physical interpretation of equation (98) which describes the mass balance in the control volume shown.

The numerical model solves for prognostic variables , , , , S, and l as a function of time, starting from a specified set of initial conditions, and forced by the wind stress and buoyancy flux at the ocean surface and prescribed transports at open lateral boundaries. These prognostic variables are staggered not only in the horizontal but also in the vertical direction. While q, l, w, , are located at levels, variables , , , S, and are staggered in the vertical and therefore located between two corresponding levels (see Figure 19). Note that w, q, l, , S, , , are located at the center of the grid, while , are staggered in the horizontal as described earlier (see also Figure 19). While shear stresses and are staggered in the horizontal in the same way as and respectively, they are however located at levels.