Re: Contours on a Gaussian grid

["Mark Verschell" <markv@xxxxxxxxxxxxxxxxxxx>]

On Sep 5,  1:22pm, beland@cerca.umontreal.ca wrote:
> Subject: Contours on a Gaussian grid
> Hello,
>
> I am trying to do a contour or shade plot of data that is on a Gaussian
> grid.  This grid has the latitude circles that are not exactly equally
> spaced.  How can I specify to ferret each latitude on the grid ?  I see
> two methods to accomplish this, although I do not know if ferret is made
> to do them:

Actually, as long as the data are located on a (pardon the term) semi-regular
grid, you can create a NetCDF file that contains your data with explicitly
declared latitudes. A reference for this is on Page 109 of the ferret manual,
or under the heading "Unevely spaced coordinates" in the online help.

I find that the easy way to do this is as follows:

1) "Fake" a regular grid, and read the data into ferret.
	yes? define axis/x=1:120:1 xfake
	yes? define axis/y=1:100:1 yfake
	yes? define grid/x=xfake/y=yfake gfake
	yes? file/var=myvar/grid=gfake mydata.dat
2) Save the data as a NetCDF file
	yes? save/file=mydata.cdf myvar
3) Dump the NetCDF file to an ASCII format file
	unix: ncdump mydata.cdf > mydata.cdl
4) Edit the NetCDF file to change the axis to unevely spaced coordinates
	Refer to the example in the FERRET manual (pages 109-117)
5) Recreate the NetCDF data file
	unix: ncgen -o mydata2.cdf mydata.cdl
6) Shade the data
	yes? use mydata2
	yes? shade myvar

Mark

-- 
-------------------------------------------------------------------------------

	      Mark Verschell (verschell@coaps.fsu.edu)
	      Center for Ocean and Atmospheric Prediction Studies
	      Florida State University
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