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Re: Grid projection scheme problem

On Wed, 16 Feb 2005, Latimer, S wrote:

> Robb,
>
>     Thanks for all of your help.  The netCDF converter works very well.
>     I now have a problem with extracting the data in the netCDF format.  We 
> (my advisor and I) tried to access the netCDF model file using IDV and it 
> displays fine.  The only problem is that I am attempting to obtain u,v wind 
> components at several levels above discrete points (i.e. lat, lon).  The hope 
> is that if we resolve the projection scheme (Lambert Conformal) we would be 
> able to automatically extract the data by use of Matlab.
>     We have tried to look at various equations in Holton (not helpful)  and 
> other sources (Penn. state, somewhat helpful) that in essence describe 
> variables like true latitude, longitude, etc. with several complex equations 
> describing how a grid point is located on the map at a particular location.  
> My advisor also tried something called the "Great Circle calculator" (method 
> found at this website 
> http://www.meridianworlddata.com/Distance-Calculation.asp   ) and found that 
> the grid does not appear to have a "regular grid spacing" in terms of 
> distance, nor does it appear to be laid out using a perfect "E-W" orientation.
>     Do you know (or know someone who might) what or how we can possibly 
> extract from discrete points the u, v wind components from several levels 
> data, given this problem or issue?

Stephen,

that's a tough question.  the idv does the conversions at a lower level
so you really don't have access to the routines to request values of
particular lat/lon locations.  when you display the data, can't you get the
values over particular lat/lon location by placing the cursor over the
location?  if it's more than a few points, this would be hard.  there is a
s/w package called MyWorld that may help you, url:

http://www.worldwatcher.northwestern.edu/myworld/


robb...

>    Thanks again for your help.
>
> Stephen Latimer
> Meteorology Graduate Student
> Texas Tech University ATMO
> Lubbock, TX 79409
>

===============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
address@hidden             WWW: http://www.unidata.ucar.edu/
===============================================================================