Re: Grid projection scheme problem

• To: "Latimer, S" <s.latimer@xxxxxxx>
• Subject: Re: Grid projection scheme problem
• From: Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>
• Date: Thu, 17 Feb 2005 15:55:00 -0700 (MST)

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
rkambic@xxxxxxxxxxxxxxxx                   WWW: http://www.unidata.ucar.edu/
==============================================================================