[gradsusr] Problem with fwrite and CTL file

[Mubashar Dogar]

Dear Doug,

Thanks a lot. Your idea works.

Regards,

Mubashar

Message: 3
Date: Tue, 31 Aug 2010 16:34:41 +0100
From: "Clark, Douglas B" <dbcl at ceh.ac.uk>
Subject: Re: [gradsusr] Problem with fwrite and CTL file
To: GrADS Users Forum <gradsusr at gradsusr.org>
Message-ID:
       <40829B0E077C1145A6DE44D39B3830A91B31A6EFC1 at nerckwmb1.ad.nerc.ac.uk>
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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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Message: 4
Date: Tue, 31 Aug 2010 12:03:19 -0400
From: Stephen McMillan <smcmillan at planalytics.com>
Subject: Re: [gradsusr] Problem with fwrite and CTL file
To: GrADS Users Forum <gradsusr at gradsusr.org>
Message-ID:
       <AANLkTik9O0TcX0gb88GjZidL8k6MNQ7q3WRsUAVS++At at mail.gmail.com<AANLkTik9O0TcX0gb88GjZidL8k6MNQ7q3WRsUAVS%2B%2BAt at mail.gmail.com>
>
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Mubashar,
Adding to Doug's comments, I noticed you initialized t at 5.  Does
that correspond to your initial January timestep?
Stephen Mc

On Tue, Aug 31, 2010 at 11:18 AM, Mubashar Dogar
<mubashardogar at gmail.com> wrote:
> 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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