Re: [ferret_users] Gridding i/j data on a lat/lon grid

[Hein Zelle <hein.zelle@xxxxxxxxxxxxx>]

Hi Vincent,

> I have a variable gridded on a i/j grid. In a separate netcdf file, I have
> the latitudes and longitudes gridded on the same i/j grid as the variable.
> I am looking for a way of putting my variable on the lat/lon grid and not
> having it in the i/j grid anymore.

Is your latitude / longitude grid regular?  I.e. do all "rows" of data
have the same longitude values, and all "columns" have the same
latitude values?

If this is the case, you can define a new netcdf file which
contains a properly gridded version of your data.  I would do it using
python, but ferret can achieve the same.  Something like


use datafile
use gridfile

let londata = longitude[d=gridfile, j=1]        ! one row only
let latdata = latitude[d=gridfile, i=1]         ! one column only
define axis /x lon=londata
define axis /y lat=latdata
let myvar = datavar[d=datafile, gx=lon@asn, gy=lat@asn]

save /file=newfile.nc myvar


If your data is on a curvilinear grid you'll need to interpolate to a
regular lon/lat grid.  There are different tools for this (matlab,
python) but usually customized.  You could also do it with ferret, using
the scat2gridgauss_xy routine.

Pyferret has a new routine CURV2RECT which does this for you.


Kind regards,
     Hein



-- 

Dr. Hein Zelle
Senior consultant meteorology & oceanography
BMT ARGOSS

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