converting HYCOM grid points to geographic coordinates

[Virginie Millien]

Hello,

Is there a way to project the HYCOM grid point data to a geographic system (lat/lon). My understanding is that I can not simply do a Mercator projection, as the HYCOM grid is not regular.

Many thanks!

Virginie

[Alan Wallcraft]

For the HYCOM tripole global grid (GLBa0.08 and GLBb0.08 - they are the same grid) there isn't a simple projection that will give you the lat,lon.  This information is in the regional.grid,[ab] "metrics" file, and a NetCDF version of the p-grid (cell center) fields is at ftp://ftp.hycom.org/datasets/GLBb0.08/expt_53.X/topo/regional_grid.nc  All the fields we provide are on the p-grid and so Latitude and Longitude from this file will give you the location of each grid point.

Note that the GLBu0.08 and GLBy0.08 grids are rectilinear - uniform spacing lat lon.  And so the netCDF dimensions are 1-D lat and lon arrays and there is a simple expression to calculate the lon,lat for any i,j.  This is why most of the native GLBb0.08 fields have been interpolated to GLBy0.08 (say).

Alan.

[Virginie Millien]

Thank you so much, I had not found the nc file with the grid and that's very useful.

Virginie