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20000106: decoding problem in dchrly???

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  • Subject: 20000106: decoding problem in dchrly???
  • Date: Thu, 06 Jan 2000 10:37:04 -0700
>From: "David J. Knight" <address@hidden>
>Organization: .
>Keywords: 200001061655.JAA27619

>Hi,
>     There seems to be a problem in decoding many South American 
>metar observations using dchrly in gempak.
>
>Specifically it does not seem to be decoding the altimeter 
>setting when given in Hpa.
>
>For example, an observation like:
>SBSN 061230Z 25002KT 9999 FEW016 SCT100 28/24 Q1010=
>produces a missing value for alti in the surface file. As I
>understand it the Q group should be the altimeter setting in Hpa.
>
>The apparently relevant code in:
>gempak5.4/src/bridge/metar/parse_metar.c
>is:
>if( Mptr->A_altstng )
>   *alti = (float)Mptr->inches_altstng;
>else
>   {
>   if( Mptr->Q_altstng )
>      *alti = (float)Mptr->hectoPasc_altstng * 1013.25 / 29.921;
>   }
>Which appears to suggest it should be working properly. (i.e. 
>it looks like it converts the Q group to alti in inches of mercury)
>
>Suggestions - help ?
>
>Thanks
>David
>
>David Knight
>Department of Earth and Atmospheric Sciences   Tel: (518)-442-4204
>SUNYA   ES-228                                 Fax: (518)-442-4494
>Albany, NY  12222                              Email: address@hidden
>


Dave,

I fixed this in a message to Robert Mullenax at:
http://www.unidata.ucar.edu/glimpse/gempak/3160

the conversion should be:
*alti = (float)Mptr->hectoPasc_altstng * 29.921 / 1013.25;

eg, flip the conversion factors.

Recompile the bridge/metar directroy to update bridge.a, then recompile
and link $GEMPAKHOME/src/programs/dc/dchrly

Steve Chiswell