[IDV #MPQ-882676]: Question about flow vectors from grids

["Unidata IDV Support" <support-idv@xxxxxxxxxxxxxxxx>]

Hi Tom-

I changed the way u and v are defined in aliases.xml and how they are used in 
the derived.xml to create the automatic derived quantities.  If I use the 
strategy that is used for the netCDF files for GRIB, it will break bundles 
because the parameter names will change.

So now, you will see a Flow Vector and a True Flow Vector for all grids 
regardless of whether they are grid relative or true.  In my experience, the 
global grids (lat/lon) are true and all the rest are grid relative.  

Let me know what you think.  Will be in the next nightly build.

Don

> On Wed, Oct 21, 2009 at 8:50 AM, Unidata IDV Support
> <support-idv@xxxxxxxxxxxxxxxx> wrote:
> > Hi Tom-
> >
> > Sorry for the silence on other issues. ÂI'll get back to you on them today.
> >
> > The problem is being able to identify whether the vectors are grid relative 
> > or true. ÂIn the netCDF files, there was a flag indicating this. ÂIn the 
> > grib messages, there hasn't been one. ÂWe are working with the netCDF 
> > group to get access to that info so we can distinguish the two. ÂRight 
> > now, the distinction is made in the aliases as to whether the u and v 
> > components map to U and V or UREL and VREL. Â I'll check with the netCDF 
> > group on the status of this and get back to you.
> >
> > Don
> >
> >> When I get some model grids (in this case, the GSM 191km AK region),
> >> the option in the "Derived" menu (in the Field Selector) is for flow
> >> vectors from the grid. ÂIf I want "grid relative" (which corrects the
> >> angle of the vectors for the direction it appears), then I have to use
> >> a formula.
> >>
> >> Since the vast majority of (model) gridded data we get has u- and
> >> v-comps in grid relative, I'm wondering why you might have chosen to
> >> not put that option in the "Derived" section?
> >>
> >> I'm asking because I'm thinking about trying to get the McV to add
> >> that to the "Derived" for McV....unless you tell me that my head is on
> >> backwards (you know, that "wrong headedness factor" again.... ;-)
> >>
> >> Thanks for any info....
> >>
> >> tom
> >>
> >> --
> >> Tom Whittaker
> >> University of Wisconsin-Madison
> >> Space Science & Engineering Center (SSEC)
> >> Cooperative Institute for Meteorological Satellite Studies (CIMSS)
> >> 1225 W. Dayton Street
> >> Madison, WI Â53706 ÂUSA
> >> ph: +1 608 262 2759
> >>
> >>
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: MPQ-882676
> > Department: Support IDV
> > Priority: Normal
> > Status: Open
> >
> >
> 
> 
> 
> --
> Tom Whittaker
> University of Wisconsin-Madison
> Space Science & Engineering Center (SSEC)
> Cooperative Institute for Meteorological Satellite Studies (CIMSS)
> 1225 W. Dayton Street
> Madison, WI  53706  USA
> ph: +1 608 262 2759
> 
> 


Ticket Details
===================
Ticket ID: MPQ-882676
Department: Support IDV
Priority: Normal
Status: Open