[ncl-talk] Fw: read grib data

[David Brown]

Hi Guo,
I am pretty sure your problem is that you tried to use the
gribtab_GLDAS2_NOAH.gtb as is. NCL uses a slightly different format for its
text file GRIB tables than the wgrib-type format used for the file you sent
me. Basically the difference is that NCL uses four colon-separated fields
instead of 3. The units, which follow the descriptor field inside square
brackets in your file, are the third field in an NCL grib table file.

I have converted your table file into an NCL-compliant file and am
attaching it here. Also I am attaching a short Python script that does the
conversion for anyone who might need it. Note it just writes to standard
output so you need to redirect it to a file. Also you need to manually add
the header line (the line that starts with -1).
You can use either
-1:-1:-1:-1
or more specifically for this file:
-1:173 :4 :130


Run it like this:
python wgrib2ncltxt.py GLDAS2_NOAH.gtb > ncl_GLDAS2_NOAH.gtb

That said, I will also be adding more validation into the NCL code, to
prevent it from crashing when it gets an invalid grib table text file.



On Wed, Jul 30, 2014 at 8:48 PM, guozfruit <guozfruit at aliyun.com> wrote:

> Thanks, Dave.
> When I set gribtable for GLDAS_v1 as the same way, it works. But when it
> comes to GLDAS_V2(they have different grib tables), error occurs. Maybe
> there is something wrong with the table?
> -Guo
>
>
> ------------------------------------------------------------------
> From:David Brown <dbrown at ucar.edu>
> Send time:Thursday, July 31, 2014 09:11
> To:guozfruit <guozfruit at aliyun.com>
> Cc:NCL <ncl-talk at ucar.edu>
> Subject:Re: [ncl-talk] Fw: read grib data
>
> Hi Guo,
>
> I am looking into this.
>  -dave
>
>
> On Wed, Jul 30, 2014 at 5:36 PM, guozfruit <guozfruit at aliyun.com> wrote:
>
>>
>>
>>
>> ------------------------------------------------------------------
>> From:guozfruit <guozfruit at aliyun.com>
>> Send time:Thursday, July 31, 2014 07:14
>> To:NCL <ncl-talk at ucar.edu>
>> Subject: read grib data
>>
>> Hi all,
>>
>> Recently I've been processing GLDAS (Global Land Data Assimilation System
>> Version 2 Products) grib data. After I set the parameter table, I have
>> error message as below:
>>
>> grib_in  =
>> addfile("./GLDAS_NOAH025SUBP_3H.A2008001.2100.001.2008197115723.grb","r")
>> Segmentation fault (core dumped)
>>
>> I'm using NCAR Command Language Version 6.2.0, I'm not sure if there is
>> something wrong with the ncl version. I also attached the parameter table.
>> Could you please help me find out what the problem is. Thanks.
>>
>> Best,
>>
>> Guo
>>
>>
>>
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>
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