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20020225: navigating UKMET grids in GEMPAK/dcgrib

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  • Subject: 20020225: navigating UKMET grids in GEMPAK/dcgrib
  • Date: Mon, 25 Feb 2002 17:03:50 -0700
David,

I decoded a file with dcgrib2, and looks OK. Try decoding with
something like:

cat ukmet_020225_00_00 | dcgrib2 -d - YYYYMMDDHH_@@@_###.gem

The international exchange grids are inverted. Its probably
not defined in dcgrib for that scan mode. Nagrib and dcgrib2 both use
the gb_ routines from gempak. 

Steve Chiswell


>From: David Ovens <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200202252342.g1PNgKx11781

>To: Support at Unidata
>
>Hello,
>
>We have been retrieving some UKMET GRIB files from ftp.ncep.noaa.gov
>directory pub/data/grib/ukmet/, filenames of the form
>ukmet_020225_12_00.  I converted to GEMPAK via dcgrib using the
>following:
>
>% source ~ldm/NAWIPS-5.6.D.1/Gemenviron
>% dcgrib -d - -m 3500 -g $GEMTBL PACK 2002022512_ukmet.gem < ukmet_020225_12_0
> 0
>Feb 25 23:22:23 dcgrib[24229]:  Using gds block for projection id:  45
> Changing center table to cntrgrib1.tbl
> Changing vertical coord table to vcrdgrib1.tbl
> Changing WMO parameter table to wmogrib2.tbl
> Changing center parameter table to ukmogrib2.tbl
>
>Then gdinfo shows
>% gdinfo
> GRID NAVIGATION: 
>     PROJECTION:          CED                 
>     GRID SIZE:          288 145
>     LL CORNER:             -90.00      0.00
>     UR CORNER:              90.00     -1.25
>
> GRID ANALYSIS BLOCK: 
>      UNKNOWN ANALYSIS TYPE 
>
>When plotted, it looks like the PMSL@0%NONE field is inverted about
>the equator.
>
>When I retrieve NCEP's GEMPAK files from ftpprd.ncep.noaa.gov in
>directory, pub/data/nccf/com/nawips/prod/ukmet.20020225/ filename
>ukmet_2002022512f000, gdinfo shows
>
> GRID FILE: ukmet_2002022512f000                                              
>                                                               
>
> GRID NAVIGATION: 
>     PROJECTION:          CED                 
>     ANGLES:                 0.0     0.0     0.0
>     GRID SIZE:          288 145
>     LL CORNER:             -90.00      0.00
>     UR CORNER:              90.00     -1.25
>
> GRID ANALYSIS BLOCK: 
>     ANALYSIS TYPE:        BARNES
>     DELTAN:               4.000
>     DELTAX:           -9999.000
>     DELTAY:           -9999.000
>     GRID AREA:           -90.00 -180.00   90.00  180.00
>     EXTEND AREA:         -90.00 -180.00   90.00  180.00
>     DATA AREA:           -90.00 -180.00   90.00  180.00
>
>and the PMSL@0%NONE field matches up nicely with the AVN, so it looks
>like NCEP can convert them to GEMPAK fine.  Can you help me figure out
>to decode the ftp.ncep.noaa.gov GRIB files properly?
>
>Thank you,
>
>David
>-- 
>
>David Ovens            e-mail: address@hidden
>(206) 685-8108          plan: Real-time MM5 forecasting for Pacific Northwest
>Research Meteorologist
>Dept of Atmospheric Sciences, Box 351640
>University of Washington 
>Seattle, WA  98195
>