The grid types for the transformations

As described in section for the different SCRIP remappings, OASIS3-MCT support different types of grids. The characteristics of these grids are detailed here:

``LR' grid`: The longitudes and the latitudes of 2D Logically-Rectangular (LR) grid points can be described by two arrays`longitude(i,j)`and`latitude(i,j)`, where i and j are respectively the first and second index dimensions. Streched or/and rotated grids are LR grids. Note that previous OASIS3 A, B, G, L, Y, or Z grids are all particular cases of LR grids.``U' grid`: Unstructured (U) grids do have any particular structure. The longitudes and the latitudes of 2D Unstructured grid points must be described by two arrays`longitude(nbr_pts,1)`and`latitude(nbr_pts,1)`, where nbr_pts is the total grid size.``D' grid`: The Gaussian Reduced (D) grid is composed of a certain number of latitude circles, each one being divided into a varying number of longitudinal segments. In OASIS3-MCT, the grid data (longitudes, latitudes, etc.) must be described by arrays dimensioned`(nbr_pts,1)`, where`nbr_pts`is the total number of grid points. There is no overlap of the grid, and no grid point at the equator nor at the poles. There are grid points on the Greenwich meridian.