Both the Global and Limited Area Models have the same resolution in the vertical. The atmosphere is divided into 19 layers, with the winds and temperatures carried at 19 levels and humidity carried at the first 16 levels. The more detailed Mesoscale Model however has 31 levels. The bottom four levels are terrain-following sigma levels, which help in application of realistic boundary conditions. The top three levels are pressure surfaces, and in between the levels are a mixture of the two, so that they gradually follow the terrain less and less and become more uniform in pressure and height.
Resolution is greatest near the surface in an attempt to model the rapid variations here.
The first layer is thinnest, being about 50 m thick. Layers above the boundary layer are 1 to 1.3 km thick, increasing to in excess of 2 km at around 12 km. The topmost level is at 40 km, in the upper stratosphere. The number of grid-points for each model is given in Table 1. Variables within the model are held on an Arakawa B-grid.