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20040420: Vietnam and GEMPAK GRIB decoding (cont.)

>From: Mai Nguyen <address@hidden>
>Organization: National Center for Hydro-Meteorological Forecasting of Vietnam
>Keywords: 200312020023.hB20N4p2027742 IDD LDM Linux GEMPAK

Hi Mai,

>I still have a 'small' question about decoding with
>dclsfc.

OK.

>The change you've done with pqact.gempak was on the
>stations table file (lsystns.upc => lsystns.combined),
>and the parameter 'EXP' after 'WMO' (see below)
> 
>> #
>> # Synoptic land reports
>> #
>> WMO
>> (^S[IM]V[IGNS])|(^SNV[INS])|(^S[IMN](W[KZ]|[^VW]))
>>      PIPE    decoders/dclsfc -v 2 -s lsystns.upc
>>      -d data/gempak/logs/dclsfc.log
>>      -e GEMTBL=/home/gempak/GEMPAK5.7.1/gempak/tables
>>      data/gempak/syn/YYYYMMDD_syn.gem
>> 
>>   to:
>> 
>> #
>> # Synoptic land reports
>> #
>> WMO|EXP
>> (^S[IM]V[IGNS])|(^SNV[INS])|(^S[IMN](W[KZ]|[^VW]))
>>      PIPE    decoders/dclsfc -v 2 -s etc/lsystns.combined
>>      -d data/gempak/logs/dclsfc.log
>>      -e GEMTBL=/home/gempak/GEMPAK5.7.1/gempak/tables
>>      data/gempak/syn/YYYYMMDD_syn.gem
>> 
>
>What difference does the 'EXP' makes? 

The LDM pattern action file(s) contain entries that will
perform some action based on:

1) a datastream name or names
2) a regular experssion tht is matched against the meta
   data for a product.

The script that reformats your GTS data into a form that
can be used by the GEMPAK decoder dclsfc also "injects"
the data into the LDM queue.  Part of the injection
process is putting the product into a known stream
type.  We used the 'EXP' (EXPerimental) feed type since
it is not used as any IDD stream.  Inclusion of EXP
in the stream type(s) will cause pqact to act on the
product using the same set of information as for data
in the WMO stream.

>+) What would happend if: after an observations from
>IDD feed had been decoded and put to the gempak file,
>the script cvtVNsyn.tcl was called and it tried to do
>the same thing with the observation of that same
>stations from our source (e.g. AAXX00)? 

I asked Chiz this earlier since it is entirely dependent
on what the decoder (dclsfc in this case) does.  He
said that the first observation for a station that
is decoded will be the one that stays in the decoded
file -- it will not be replaced by the decoder.  The
only circumstance under which the second observation
will be used to replace/update the first is if it is
a correction.  The observations I saw in your example
data files (AAXXnn) were not corrections or specials.

>  a) the new entry would overide the old one in the
>gempak file

No, not unless it was a correction/special

>  b) dclsfc will ignore that station but continue with
>other data

Yes.

>  c) There will be an error and dclsfc would quit

It shouldn't quit.

>This question arised because after i ran cvtVNsyn.tcl
>manually, it seems like dclsfc was not called (by
>pqact) as often.

As I understand the GEMPAK decoders, they keep running
waiting for new data to arrive.  I believe that if
you look at a listing of programs running on met_research3
you will see dclsfc running all of the time.  The reason
that the action in pqact.conf was changed to include
decoding observations from the EXP feed was so that
only one invocation of dclsfc would run at a time.
It is _bad_ if more than one instance of a decoder
runs at the same time for the same output file.  The
typical result in such a case will be the corruption
of the output data file.

>+) Another question about NMAP2 configuration.
>As Chiz explained, the configuration is defined in
>$GEMTBL/config/prmlst.tbl. But it appears that it
>doesn't take all the parameters defined in there.
>
>In fact, I would like to draw map that have a box
>surrounded, and some specific title. As I've read in
>the manual, it is defined by setting the parameters 
>
>PANEL = 0/1
>TITLE = ...
>
>But it has no effect after i've put in prmlst.tbl.
>
>So the question is: 
>+ Are the above parameters the ones that I need to
>set?
>+ Where they need to be set?

I will leave these questions for Chiz to answer.

>+) About decoding our model HRM. I didn't see the line
>which refers to pqact.conf in ldmd.conf. Have you done
>that somewhere else or I'll have to do that?

The default configuration file that pqact uses is
~ldm/etc/pqact.conf.  The ldmd.conf entry on met_research3:

exec    "pqact -f EXP"

will use the default pqact.conf file for all products in
the EXP feed type.  This line could have been equivalently
written as:

exec    "pqact -f EXP etc/pqact.conf"

>Thank you very much as always.

No worries.

Cheers,

Tom
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