| Re: Point Observations from NARR output [message #75752] |
Thu, 07 April 2011 17:11  |
B.J. Baule
Messages: 3
Registered: April 2011
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Junior Member |
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On Apr 7, 5:06 pm, "Kenneth P. Bowman" <k-bow...@null.edu> wrote:
> In article
> < ae2b9885-d9aa-42b6-b3d5-6418072f1...@f11g2000vbx.googlegroup s.com >,
> "B.J. Baule" <guitarplayer_...@comcast.net> wrote:
>
>> Hello all,
>
>> This is probably a really simple problem however my inexperience
>> with IDL has left me baffled. I'm relatively new to IDL programming
>> and have a question regarding getting grid point values from NARR
>> reanalysis output. I can get the data to open, read in, and make a
>> map. However, I would like to get point observations from the
>> reanalysis data set (Ex. July Temperature for Barrow, AK Lat:
>> 71.2905556 Lon:-156.7886111).
>
> I suggest that you compute the great circle distance between
> Point Barrow and all of the longitude-latitude points on the
> NARR grid. Then find the minimum. You only have to do this once.
> That will tell you which grid point is closest to Barrow.
>
> If you insist on interpolating to Barrow, you will have to
> do that in Cartesian coordinates on the Lambert conformal grid.
> Probably not worth it, in my opinion.
>
> To compute great circle distance use MAP_2POINTS. (One of my
> nominations for least-intuitive and least-mnemonic routine name
> in IDL.) You will spend half an hour trying to get all of
> the units and keywords right, but it does work.
>
> Ken Bowman
Thanks Ken. I'll give this a try tomorrow. :)
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