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20041202: 20041201: GEMPAK trouble with non-standard domain



Brian,

Since this is not grid #252, that value should be set to 255
just for correctness, but since the dcgrib2 decoder will use the GDS
when present, that shouldn't be your problem here.

One possibility is that the Lo1 angle is not in the range 0 to 360,
eg your wgrib output shows 520. Can you change this to a more
conventional 260? That way, the (Lo1 - Lov) difference in
computing the upper right point should be in the correct distance.

Steve Chiswell
Unidata User Support




>From: Brian Jamison <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200412021637.iB2GbRlI011630

>Hello Steve!
>
>> Brian,
>>
>> The dcgrib decoder is depricated in favor of dcgrib2,
>> so I'll suggest you use that.
>
>Ok, I created a new GEMPAK format file using dcgrib2.
>
>> Also, it would help to look at the gdinfo output for
>> the grid navigation and projection used in the GEMPAK file
>> which is created by the decoder. It sounds as if the navigation in the
>> file is not as expected, or doesn't match the PROJ and GAREA you  
>> provided
>> for GDCNTR. Note that you can use PROJ=def and GAREA=grid.
>
>Here is the gdinfo output:
>
>  GRID FILE: /home/mab/jamison/gempak/0104800000000.gem
>
>  GRID NAVIGATION:
>      PROJECTION:          LCC
>      ANGLES:                25.0  -169.0    25.0
>      GRID SIZE:          301 225
>      LL CORNER:              16.00    160.00
>      UR CORNER:             -36.88    150.08
>
>  GRID ANALYSIS BLOCK:
>       UNKNOWN ANALYSIS TYPE
>
>  Number of grids in file:   745
>
>  Maximum number of grids in file:   5000
>
>  [GDU 2]  Did not find any matching grids.
>  Parameters requested: GDFILE,LSTALL,OUTPUT,GDATTIM,GLEVEL,GVCORD,GFUNC.
>
>It appears that the UR corner is really off.  I set this value through
>garea, but I guess that it is being ignored in favor of the GDS
>block of the grib file?
>
>Using wgrib -V, here is one header block of info from the grib file:
>
>rec 1:0:date 2001021700 PRES kpds5=1 kpds6=109 kpds7=1 levels=(0,1)  
>grid=252 hybrid lev 1 anl
>:
>   PRES=Pressure [Pa]
>   timerange 0 P1 0 P2 0 TimeU 1  nx 301 ny 225 GDS grid 3 num_in_ave 0  
>missing 0
>   center 59 subcenter 0 process 105 Table 2
>   Lambert Conf: Lat1 16.000000 Lon1 520.000000 Lov 191.000000
>       Latin1 25.000000 Latin2 25.000000 LatSP 0.000000 LonSP 0.000000
>       North Pole (301 x 225) Dx 20.318000 Dy 20.318000 scan 64 mode 8
>   min/max data 78529 102848  num bits 15  BDS_Ref 78529  DecScale 0  
>BinScale 0
>
>> In general, if the GDS block of the grib provides the navigation,
>> then that is used instead of any found in $GEMTBL/grid/grdnav.tbl.
>> Dcgrib2 should have no trouble with this in any regard.
>
>I see that the LL corner point is provided.  Should the grib file
>also provide the UR corner?  Can the GEMPAK decoder compute
>it using the projection information and the dx and dy?
>
>> One possibility of confusion for dcgrib (not dcgrib2) would be if the
>> grid was displaced, but it still used the grid #252 projection number
>> in the grib PDS block.
>
>It appears that the file does have 252 set for the grid, but I am still
>getting the same errors after decoding the grib file with dcgrib2.
>
>
>Brian
>
>
>
>>> From: Brian Jamison <address@hidden>
>>> Organization: UCAR/Unidata
>>> Keywords: 200412012035.iB1KZMlI011579
>>
>>> Hello!
>>>
>>> I am a new user of GEMPAK, and have been through the
>>> on-line tutorial.  I am interested in using GEMPAK to look
>>> at particular fields in the RUC 20km model.
>>>
>>> Here is my problem:  we have some RUC forecasts that
>>> were generated over a displaced area, namely over the
>>> Pacific just northwest of Hawaii.  All other aspects of the
>>> forecasts are identical to a RUC run over the CONUS, the
>>> only difference is the domain.
>>>
>>> I (apparently) successfully created the GEMPAK format file
>>> from the RUC GRIB file using the DCGRIB decoder, however
>>> I am getting errors when trying to create plots using this file.
>>> The errors are as follows:
>>>
>>>  GEMPAK-GDCNTR>r
>>> Creating process: xw for queue 502
>>>  [GEMPLT -16]  NIPBND - Invalid projection bounds.
>>>  [GR -7]  Error defining grid navigation in GEMPLT.
>>>  [DG -30]  Error opening grid file.
>>>
>>> I set the parameters for PROJ and GAREA to reflect the position
>>> of the displaced domain, but still get these errors.
>>>
>>> What can I do to get around this?  Any help you can give is
>>> greatly appreciated.
>>>
>>>
>>> Brian Jamison
>>>
>>>
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