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19990709: GEMPAK vector components

John,

To get the grid relative components of GEO, you can use:
UR(GEO) and VR(GEO) (similarly UN() and VN() for north relative
components).

Steve Chiswell
Unidata User SUpport

>From: John Knox <address@hidden>
>Organization: .
>Keywords: 199907091936.NAA06777

>Dear Steve/support,
>
>We have a new question for you re: GEMPAK:
>
>How does one get the *components* of the geostrophic wind?  
>We have need of calculating the Jacobian of the geostrophic 
>wind, but there is no 'ugeo' or 'vgeo' comparable to 'uwnd' 
>or 'vwnd' to stick into the Jacobian function.  We ran into 
>this problem some months ago and still haven't figured out 
>how to get around it... but there must be a very easy way 
>to do so.
>
>Thanks!
>
>John
>
>On Fri, 2 Jul 1999 15:58:23 -0600 Steve Chiswell 
><address@hidden> wrote:
>
>> 
>> John,
>> 
>> All of the GEMPAK GD programs utilize a Gempak gridded data file
>> such as is created by nagrib or dcgrib for model data, or one
>> that had objectively analyzed observations such as would be
>> output from oabsfc or oabsnd for surface and upperair data
>> respectively. The file name extension is not important
>> in identifying the file type contents.
>> 
>> Unidata provides a "decoders" package:
>> ftp://ftp.unidata.ucar.edu/pub/decoders/decoders.tar.Z
>> 
>> The program gribtonc (grib to netcdf) is commonly used by Unidata sites
>> to decode GRIB data into a NetCDF format file. This program is akin
>> to dcgrib in that is decodes grib data into a specific output file type.
>> You can find documentation on the decoders package as well as NetCDF on
>> our WWW page.
>> 
>> Steve Chiswell
>> Unidata User Support
>> 
>> 
>> 
>> 
>> On Fri, 2 Jul 1999, John Knox wrote:
>> 
>> > Dear Steve,
>> > 
>> > Thanks for the message.
>> > Quick follow-ups:
>> > 
>> > 1) gdlist requires a .grd file; how is that file created?
>> > 
>> > and
>> > 
>> > 2) what are the steps toward creating a NetCDF version of 
>> > the raw grid data?  Can I find this in documentation 
>> > somewhere instead of bugging you?
>> > 
>> > Thanks, and have a great holiday weekend,
>> > 
>> > John
>> > 
>> > On Thu, 1 Jul 1999 17:38:31 -0600 Steve Chiswell 
>> > <address@hidden> wrote:
>> > 
>> > > John,
>> > > 
>> > > It depends on the type on input needed by your 3D package
>> > > as to what you would output.
>> > > 
>> > > You can use gdlist to output data to an ascii file with
>> > > OUTPUT=f/filename. You could also write a program to read the gempak dat
> a
>> > > file using routines provided in the gempak library and write it into
>> > > whatever format your needed. Also, there are some programs called gemvis
>> > > (not part of gempak) that can convert the gempak data into Vis-5D format
> .
>> > > Otherwise, if you have the raw grid bata, you can convert it into NetCDF
>> > > format and many packages like IDL, NCARGraphics, matlab etc can read
>> > > NetCDF files.
>> > > 
>> > > In general, you can always send questions to address@hidden.
>> > > If I'm on vacation or out of the office, someone else may get to your
>> > > question quicker than myself. Also, there is the gembud mail list where
>> > > you might be able to get information on how other Unidata sites are
>> > > solving the problem.
>> > > 
>> > > Steve Chiswell
>> > > Unidata User Support
>> > > address@hidden
>> > > 
>> > > 
>> > > 
>> > > On Thu, 1 Jul 1999, John Knox wrote:
>> > > 
>> > > > Steve,
>> > > > 
>> > > > Thanks for all your help with GEMPAK.
>> > > > Now, a new question: let's say we want to do some 3D 
>> > > > visualization of the data.  If we want to put a subset of 
>> > > > the data into a file for use with another software package, 
>> > > > how is that done [if it's doable]?  
>> > > > 
>> > > > Also: should I be bugging you with these questions?  I feel 
>> > > > like our needs are at a pretty basic level, but I've not 
>> > > > been successful at answering them via the Web so far.
>> > > > 
>> > > > Thanks,
>> > > > 
>> > > > John
>> > > > 
>> > > > 
>> > > > 
>> > > 
>> > 
>> > ------------------------------------------------
>> > Dr. John A. Knox
>> > Assistant Professor of Geography and Meteorology
>> > Room 15, Mueller Hall
>> > Valparaiso University
>> > Valparaiso, IN 46383
>> > E-mail: address@hidden
>> > Office Phone: 219-464-6003
>> > 
>> > 
>> 
>
>------------------------------------------------
>Dr. John A. Knox
>Assistant Professor of Geography and Meteorology
>Room 15, Mueller Hall
>Valparaiso University
>Valparaiso, IN 46383
>E-mail: address@hidden
>Office Phone: 219-464-6003
>