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Geodesic Grids

Non-Uniform Grids and Triangular Mesh Conversion

The GEODESIC grid used in the examples on this page is non-uniform grid. It is better to convert this grid to a triangular mesh rather than interpolate it to a uniform grid before contouring. Note that only contouring is available with triangular mesh conversion at this time.

If the input array to a gsn_csm graphical interface is one dimensional, NCL automatically uses triangular mesh conversion. The lat/lon information must be provided by setting:
sfXArray and sfYArray.

geodesic_1.ncl: sfXArray and sfYArray are set to the model's grid_center_lat/lon converted to degrees. sfXCellBounds and sfYCellBounds are set the model's grid_corner_lat/lon converted to degrees.

The second image shows the structure of a GEODESIC grid, along with its cell centers.

geodesic_2.ncl: gsnPolar selects the hemisphere, either "NH" or "SH". mpMinLatF adjusts the minimum latitude. Note that if plotting over the southern hemisphere, then mpMaxLatF must be used.