non-Uniform Grids and Triangular Mesh Conversion
The adaptive grid used in the examples on this page is a non-uniform grid. It is better to convert this grid to a triangular mesh (available since NCL version 4.2.0.a032) rather than interpolate it to a uniform grid before contouring.
For more information on non-uniform grids that NCL can handle, see the document "Non-uniform grids that NCL can contour."
If the input array to a gsn_csm graphical interface is one- dimensional, and also has one-dimensional lat/lon arrays of the same length, NCL automatically uses triangular mesh conversion. The lat/lon information must be provided by setting sfXArray and sfYArray.