[gradsusr] Enc: regriding problem

Tue Nov 8 17:47:29 EST 2011

Arlindo,

  I have a GPCP option in lats4d.sh; enter

% lats4d.sh -h

for the correct option.

Sent from my iPhone

On Nov 8, 2011, at 4:59 PM, Arlindo Meque <mequitomz at yahoo.com.br> wrote:

The lats4d.sh script worked properly. The only problem is that the output
from the lats4d.sh is a file with 144 points in x-direction and 73 points
in y-direction while my observation file (gpcp) has 144 points in
x-direction and 72 points in y-direction, i.e, the number of points in
y-direction from the forecast and observation differ by 1.

I’ve tried again the re()  command but the but GrADS fail  to discern the
coordinates:
ga-> sdfopen  forecast.nc
Scanning self-describing file:  forecast.nc
SDF file forecast.nc is open as file 1
LON set to 0 360
LAT set to -90 90
LEV set to 0 0
Time values set: 2009:9:16:0 2009:9:16:0
E set to 1 1
ga-> define gg=re(precip,144,linear,0,2.5,72,linear,-90,2.5,bl)
Define memory allocation size = 82944 bytes
ga-> set sdfwrite test.nc
SDFWrite file name = test.nc
SDFWrite will replace an existing file
SDFwrite file will have same number of dimensions as defined variable
ga-> sdfwrite gg
Wrote variable gg to test.nc
ga-> reinit
No hardcopy metafile open
All files closed; all defined objects released;
All GrADS attributes have been reinitialized
ga-> sdfopen test.nc
Scanning self-describing file:  test.nc
SDF file has no discernable time coordinate -- using default values.
SDF file test.nc is open as file 1
LON set to 0 360
LAT set to -90 87.5
LEV set to 0 0

------------------------------
*De:* Jennifer Adams <jma at cola.iges.org>
*Para:* GrADS Users Forum <gradsusr at gradsusr.org>
*Enviadas:* Terça-feira, 8 de Novembro de 2011 12:13
*Assunto:* Re: [gradsusr] Enc: regriding problem

On Nov 7, 2011, at 2:46 PM, Arlindo da Silva wrote:

On Mon, Nov 7, 2011 at 10:11 AM, Arlindo Meque <mequitomz at yahoo.com.br>wrote:

  Dear  all,

1. I have a forecast file (1.875X1.25)  with 192 points in x-direction and
145 points in y-direction. I am trying to regrid the file to match the
observation (2.5X2.5) with 144 points in x-direction and 72 points on
y-direction

2. I am able to create the  regridded file, the problem is  that the
dimensions of the regridded file do not much those of the observation file,
so I am not able to make the diffidence between the forecast and the
observation.

3. Please find attached the forecast and observed file along with the
regriding script.

This more of a question for Jeniffer as I am not sure how sdfwrite figures
out the coordinate variables of the output file (does it use the
coordinates of the default file?).

The sdfwrite copies the coordinate information from the default file at the
time the 'define' command was invoked.
I have no idea what the re() function does when it returns the new grid. If
you used lterp instead, you would have the right coordinate info because
it's attached to the destination grid expression.

Since you are using opengrads, Arlindo's suggestion to use lats4d may also
do what you need.
--Jennifer

Now, a simple way to produce a file interpolated to this particular grid is
to use lats4d:

% lats4d.sh -i forecast.nc -o fcstregridded -ncep2.5 -v

This is going to the standard NCEP 2.5x2.5 grid (which is not exactly what
you had on your re() line). Are you sure your re() line is correct? It is
kind of an unusual grid. In any event, if you would like to modify the
output from ncep2.5 there is a simple way, but let me hear from you first.

      (the other) Arlindo

-- 
Arlindo da Silva
dasilva at alum.mit.edu
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org

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