[gradsusr] Problem with fwrite and CTL file

[Clark, Douglas B]

Mubashar,

Is the file you wrote the correct size? (e.g. use 'ls -l' on unix)
I think you might find that it is slightly larger than expected because, I think, GrADS might repeat data around 0degE because of the way it sets the dimensions for a default global plot.
Use 'q dims' to see what the x grid cords are before the fwrite step. You might get something like "0 to 144" rather than the "1 to 144" you might expect. Then either explicitly add 'set x 1 144' in your script, or rewrite your final ctl file to have (say) 145 x points.

I'm guessing all this because I have made similar mistakes in the past!

Doug


From: gradsusr-bounces at gradsusr.org [mailto:gradsusr-bounces at gradsusr.org] On Behalf Of Mubashar Dogar
Sent: 31 August 2010 16:19
To: gradsusr at gradsusr.org
Subject: [gradsusr] Problem with fwrite and CTL file

Dear GrADS Users,

I have downloaded ECMWF (ERA40) data for surface temperature at 2.5 by 2.5 resolution for years 1958-2001. My intention was to see the trend for the month of January only. So I extracted all the Januaries between 1958-2001 in a binary/dat file by using the following commands in GrADS. When I tried to open this file by making a CTL (choosing the same x & y dimentions) and display January of any one year, the spatial picture is not the same as if I display the same January in original data file. Could you please help me?

Here is the script to create a binary/dat file
'reinit'
'open EraT2M.ctl'
'set gxout fwrite'
'set fwrite January.dat'
t=5
*tmax=6
tmax=532
while(t<=tmax)
'set t 't
'd no2tsfc-273.15'
t=t+12
endwhile
'disable fwrite'
'reinit'

Here is the control file to open the above January.dat file
DSET    january.dat
TITLE     Sample Data Set
UNDEF    -9.999E33
*OPTIONS    big_endian
OPTIONS   little_endian
*OPTIONS   template
xdef 144 linear 0 2.5
ydef 73 linear -90 2.5
ZDEF      1 LINEAR 1 1
TDEF     44 LINEAR 1JAN1958 1mon
VARS      1
no2tsfc 0  99  Surface Temperature_2m
ENDVARS


Regards,

Mubashar
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