[ferret_users] Regridding from a regular grid to natural coordinates defined by along/cross isotherms, isobars, bathymetry, streamlines etc.

["'Drijfhout, S.S. (Sybren)' via _OAR PMEL Ferret Users" <ferret_users@xxxxxxxx>]

I have various field in (x,y) coordinates from an ocean model.

I want to regrid some of these fields  (in a limited area) onto some sort of natural coordinate system. This could be based on isotherms, isopycnals, isobaths, SSH, barotropic streamfunction contours, etc.

 In my particular problem I want the coordinates to be along and across a curve that defines the edge of the continental shelf around Antarctica.

 I already possess a file that defines this edge: shelfmask.nc; including the variable cs60.

I can find the j value at each i-point of the edge by: j1=cs60[j=1:400@loc=3], that is, cs60 is only 3 at the shelf-edge and has other values everywhere else.

In theory I have to map xv(i,j) to xvnew(I,jstar)  with jstar=j-j1

Ferret wants me to define a new y-axis but does not allow me to define ystar by a let command, and using j and ja gives errors because of recursive problems.  

Has anybody experience with regridding to something like streamline-coordinates and/or does anybody know how to perform such a regridding operation in ferret?

 

Sybren