Processing Converted GRIB2 Data

[Sestak, Dr. Michael]

Specifically, grib2ctl.pl generally produces bad tdef lines.  You have to
change the tdef to what you actually want, then run gribmap, not run
gribmap, then change the tdef.

-----Original Message-----
From: Mike Fiorino [mailto:fiorino at LLNL.GOV]
Sent: Thursday, August 11, 2005 12:56 PM
To: GRADSUSR at LIST.CINECA.IT
Subject: Re: Processing Converted GRIB2 Data


your need to rerun gribmap ... Mike

> -----Original Message-----
> From: GRADSUSR at LIST.CINECA.IT
> [mailto:GRADSUSR at LIST.CINECA.IT] On Behalf Of Eric Konieczny
> Sent: Thursday, August 11, 2005 12:33 PM
> To: GRADSUSR at LIST.CINECA.IT
> Subject: Processing Converted GRIB2 Data
>
> Dear GrADS users,
>  I am trying to process an NDFD GRIB2 dataset with GrADS.
> The dataset is packed with only one variable and has multiple
> time steps.
> First, I converted the GRIB2 file to GRIB1, using NCEP's
> cnvgrib v. 1.1.1 converter.  Next I created the .ctl file
> using grib2ctl and the corresponding .idx file with gribmap.
> Grib2ctl produced the following control file:
>
> dset ^newGRIB1.grb
> index ^newGRIB1.grb.idx
> undef 9.999E+20
> title newGRIB1.grb
> *  produced by grib2ctl v0.9.12.5p33f
> dtype grib 255
> pdef 1073 689 lcc 20.191000 238.445000 1 1 25.000000
> 25.000000 265.000000
> 5079 5079
> xdef 1073 linear 238.445000 0.0491959539055032 ydef 689
> linear 20.191000 0.0461727272727273 tdef 1 linear
> 14Z08aug2005 1mo zdef 1 linear 1 1 vars 1 TCDCsfc  0 71,1,0
> ** surface Total cloud cover [%] ENDVARS
>
> The tdef line is produced for whatever reason incorrectly, so
> I tried changing it to what it should be:
> tdef 36 linear 14Z08aug2005 3hr
>
> I can open the .ctl file in GrADS and display the variable at
> the first time instance (t=1), but when I switch to another
> time step, an error occurs.
>
> ga-> open data/newGRIB1.ctl
> Scanning description file:  data/newGRIB1.ctl Data file
> data/newGRIB1.grb is open as file 1 LON set to 238.445
> 291.183 LAT set to 20.191 51.9578 LEV set to 1 1 Time values
> set: 2005:8:8:14 2005:8:8:14
> Notice: Implied interpolation for file data/newGRIB1.ctl
> Interpolation will be performed on any data displayed from this file
>
> ga-> set t 2
> Time values set: 2005:8:8:17 2005:8:8:17
> ga-> d tcdcsfc
> Notice:  Automatic Grid Interpolation Taking Place GRIB I/O
> Error: Bit Map I/O Data Request Error:  Error for variable 'tcdcsfc'
>   Error ocurred at column 1
> DISPLAY error:  Invalid expression
>   Expression = tcdcsfc
>
> Obviously there are some issues with accessing the multiple
> time steps.
> To further investigate this I ran an inventory on the GRIB1
> file with both wgrib and degrib (from the MDL).  While degrib
> seemed to recognize the different time steps, wgrib did not.
>
> Has anyone else had success reading a GRIB2 dataset
> (converted to GRIB1) in GrADS?  Is there some other change
> that I need to make in the .ctl file?  Any ideas/suggestions
> would be greatly appreciated.
>
> Thanks in advance,
> Eric Konieczny
>