VERY IMPORTANT: Updated nesting connetivity tool contact.m

[arango]

This is an essential update to the ROMS nesting connectivity tool contact.m. In particular, the local function refine_coordinates is enhanced to be more robust for Cartesian and Spherical nested grid applications when computing ROMS metric variables.

I added the following critical information to contact.m header:

Users need to be aware of potential problems with spherical grids because we do not know how the grid generation tool computed the ROMS metrics (pm, pn, and angle) for all nested grids. Therefore, any procedure here will not exactly conserve coarse-to-fine area because of inconsistent (lon, lat) distance methodology. One possible solution is to recompute the ROMS metrics for all grids using roms_metrics.m based only on its (lon, lat) coordinates. Thus, we have an invariant way in the computation of the ROMS metrics in all the nested grids before running this tool. See roms_metrics.m for methodology details.

• Deprecated function grid_metrics.m is removed from the repository to avoid any confusion in the future. It is replaced with more robust function roms_metrics.m.

• coarse2fine.m is also updated to use roms_metrics for consistency.

[arango]

Corrected bugs in coarse2fine.m. Many thanks to John Wilkin for reporting these issues.

[arango]

Corrected nc_drename.m to put the NetCDF file into define mode before the dimension is renamed:

% Put file into define mode.

netcdf.reDef(ncid);