[GEMPAK #HXQ-905345]: gem to grib conversion

Megan,

The good news is that your grib1 files are written correctly, the bad news is 
that you're seeing this small projection in IDV due to a bug in how IDV reads 
the grib1 file (currently being fixed).  So if you're using these grib1 files 
as input for the WRF be sure that they are written correctly.

Best,

Michael James
Unidata User Support



> Hi,
> 
> Thanks for looking into my problem.  I was able to use IDV to open these
> files without any trouble, but this is the first time I've used IDV so I'm
> not sure what the problem might be.
> 
> Also, eventually I'd like to modify this temperature field (in gem format)
> and then write it back to grib for use in the WRF model.  So I wanted to
> make sure I could do this conversion without TMPK being changed much by
> the conversion process itself.  That's my goal in converting TMPK just to
> write it back again.
> 
> I've also noticed that TMPK looks fine when the modified grib is converted
> back to gem.  I think there are 2 TMPK grids (at the same level and
> vertical coordinate) in my modified grib file.  The fields available in
> IDV indicate that the original TMPK field is there in addition to the one
> I wrote (at a different projection).  Therefore, when it's converted back
> to gem and TMPK is displayed, I'm not sure which one I'm looking at, the
> original or the one I wrote.
> 
> I hope this clears up any questions you had.  I'll let you know if I make
> any progress.
> 
> Thanks again,
> Megan
> 
> 
> > Hi Megan,
> >
> > I've been playing around with this problem for a bit, unfortunately I've
> > been unable to load these GRIB1 files in IDV.  Is there a table that
> > you're using that is required?
> >
> > Otherwise, my next question would be, is this problem only occurring while
> > trying to add the TMPK grid to your GRIB1 file?  If so, why not simply
> > plot TMPK directly from the GRIB1 file or the GEMPAK file?   When I use
> > dcgrib2 to convert modified_fnl_060807_00_00 to
> > modified_fnl_060807_00_00.gem (GEMPAK format) I'm able to see the
> > worldwide TMPK field without problem using GDPLOT2.
> >
> > Send along any more information that you think will help, I'll do my best
> > to diagnose this problem but it may not be until early next week when I
> > can go to some of our IDV people for more help.
> >
> > Best,
> >
> > Michael James
> > Unidata User Support
> >
> >> Hi,
> >>
> >> I have been attempting to convert a grib file to gempak format, write
> >> some
> >> new grids to it and then convert it back to grib.  However, the new
> >> grids
> >> in the end-product grib file appear to be a different navigation than
> >> the
> >> ones in the original grib.
> >>
> >> I use dcgrib2 to convert my original grib to gem.  I then copy my
> >> original
> >> grib file to a new name, and then use gdgrib to write the 500-mb tmpk
> >> grid
> >> from the gempak file to this new grib file.
> >>
> >> GDFILE   = fnl_060807_00_00.gem
> >> GFUNC    = TMPK
> >> GDATTIM  = last
> >> GLEVEL   = 500
> >> GVCORD   = pres
> >> GBTBLS   =
> >> GBFILE   = modified_fnl_060807_00_00
> >> VERCEN   =
> >> PDSVAL   = TMPK%pres@500
> >> PRECSN   = d/5
> >> WMOHDR   =
> >> CPYFIL   = fnl_060807_00_00.gem
> >> PROJ     = CED
> >> GRDAREA  = -90;-180;90;180
> >> KXKY     = #1;1
> >>
> >> When I look at this modified grib file in IDV, the 500-mb temperature
> >> grid
> >> I've written is in a different projection.  The original grid had a
> >> lat/lon extent of -90 to 90 and -180 to 180; this new grid covers -90.2
> >> to
> >> -90 and -0.4 to 0.
> >>
> >> This data is the 1x1 degree FNL data available from the WRF users page
> >> (http://www.mmm.ucar.edu/wrf/users/download/free_data.html). And I've
> >> put
> >> the relevant files on a webserver:
> >> at:http://tempest.meas.ncsu.edu/megan/gemhelp/
> >>
> >> If you could suggest how to perform this conversion with the grid
> >> navigation intact, I'd really appreciate it.
> >>
> >> Megan Gentry
> >>
> >> ----------------------------------------------------
> >> Megan S. Gentry
> >> Graduate Research Assistant, Forecasting Lab
> >> Department of Marine, Earth and Atmospheric Sciences
> >> North Carolina State University
> >> More info: http://www4.ncsu.edu/~msgentry/
> >>
> >>
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: HXQ-905345
> > Department: Support GEMPAK
> > Priority: Normal
> > Status: Open
> >
> >
> 
> 
> ----------------------------------------------------
> Megan S. Gentry
> Graduate Research Assistant, Forecasting Lab
> Department of Marine, Earth and Atmospheric Sciences
> North Carolina State University
> More info: http://www4.ncsu.edu/~msgentry/
> 
> 


Ticket Details
===================
Ticket ID: HXQ-905345
Department: Support GEMPAK
Priority: Normal
Status: Open