Re: Regridding from low to high resolution ?

Hi Madeleine,

I just wanted to throw in a quick caveat not having to do with the coding:
 when interpolating, it is generally not such a good idea to interpolate
from a coarse grid to a finer grid, because the points on the fine grid are
being filled with "phantom" data that might not accurately reflect what the
fine grid would actually contain if the dataset in question was created
using the fine grid in the first place. If you have two datasets with
different grids and want to interpolate one to the other for whatever
reason, you should interpolate the fine grid to the coarse one, not vice
versa, and if you are just regridding one field to get a denser dataset,
that you have to take the finer grid with a grain of salt, especially if
the finer grid is a lot finer than the coarse one.

Danny

On Thu, Jun 14, 2012 at 2:46 PM, Madeleine Patterson <
madeleine.patterson77@gmail.com> wrote:

> Hi Mary,
>
> Sorry about the cluenessness about ncl-talk etiquette!
>
> I have set up the function declaration at the start of the code, before
> the main script, but am unsure of what I need to do to implement the
> function and where, in the main body of the script (i.e. after I've open
> files and read variables into variable names, etc.)
>
> In your example below, I would -after opening files and reading in
> variables -define clon, clat, tlon and tlat, but what do I do then? use the
> regrid_cat function that I've already defined (and if so, how?), as well as
> the 'testd=grid2triple()...' and 'pctpftnew=triple2grid()...' commands?
>
> In grid2triple command, 'z' should be 2-d, but in my case it is 3-d (10
> pfts, 91 lats, 144 lons)
>
> Is there an example script you could point me to that creates a function
> and implements it later in the script?
>
> Thanks,
> M
>
> ******
> You are missing a "begin" after the "function" declaration.
>
> In general, I would recommend not putting a function declaration right in
> the middle of your main program. It's cleaner to do it like this:
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
>
> undef("regrid_cat")
> function regrid_cat(clat[*],clon[*],pctpft[*][*],tlat[*],tlon[*]) ;
> categorical grid and target grid
> begin
> testd=grid2triple(clon,clat,pctpft) ; testd(3,ld)
> pctpftnew = triple2grid(testd(0,:),testd(1,:),testd(2,:),tlon,tlat,False)
>
> copy_VarAtts(pctpft,pctpftnew) ;contributed.ncl
> cnew!0 = "lat"
> cnew!1 = "lon"
> cnew&lat =tlat
> cnew&lon =tlon
>
> return(pctpftnew)
> end
>
>
> begin
>
> setfileoption("nc","SuppressClose",False)
>
> in1 = addfile("pft_file1.nc","r")
>
> pctpft = in1->PCT_PFT
>
> clat=90
> clon=144
> tlat=360
> tlon=720
> . . .
>
> end
>
>
>
>
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Received on Thu Jun 14 15:03:23 2012