[ncl-talk] question on nearest point functions in NCL

[Mary Haley]

​Hi ​
Juan,

I think that wrf_user_ll_to_ij may be what you want:

http://www.ncl.ucar.edu/Document/Functions/WRF_arw/wrf_user_ll_to_ij.shtml

If you want to see an example of how a function is used in a real script,
head over to:

http://www.ncl.ucar.edu/Applications/

and then click on the "functions/procedures" link at the top of the in this
sentence:




*List of tips, resources, functions/procedures and the example scripts they
appear in.*

​This will take you to​ a long page that can take awhile to load:

http://www.ncl.ucar.edu/Applications/func_list.shtml

​and you can use your browser search window to look for
"wrf_user_ll_to_ij", or just tack it onto the end of the URL:

http://www.ncl.ucar.edu/Applications/func_list.shtml#​wrf_user_ll_to_ij

​You will see a list like this:

wrf_user_ll_to_ij
    dataonmap_zoom_10.ncl
    shapefiles_14_mask.ncl
    wrf_debug_1.ncl (WRF debugging)
    wrf_debug_2.ncl (WRF debugging)
    wrf_debug_3.ncl (WRF debugging)
    wrf_debug_4.ncl (WRF debugging)
    wrf_gsn_10.ncl (WRF gsn_csm)
    write_csv_5.ncl (Writing CSV files)


This shows various NCL scripts and the page they appear on in parentheses.
I recommend clicking on the page in the parentheses so you can see a
description of the example. For example, "WRF_gsn_csm":

http://www.ncl.ucar.edu/Applications/wrfgsn.shtml#ex10

which describes wrf_user_ll_to_ij along with two other methods for getting
i/j indexes from a lat/lon point.

As a new user working with WRF data, I recommend looking at the WRF
examples page:

http://www.ncl.ucar.edu/Applications/wrf.shtml

which has links to several other pages with lots of NCL scripts and
descriptions of what they do.

You may also want to check out the excellent and extensive NCL User
Guide (NUG),
created by Karin Meier-Fleischer and Michael Böttinger of DKRZ
<https://www.dkrz.de/> (Deutsches Klimarechenzentrum).

*https://www.ncl.ucar.edu/Document/Manuals/NCL_User_Guide/
<https://www.ncl.ucar.edu/Document/Manuals/NCL_User_Guide/>*


Good luck,

--Mary

​



On Wed, Feb 28, 2018 at 7:49 AM, Juan Carlos Anduckia <janducki at yahoo.com>
wrote:

> Hello:
>
> I'm new to the list and to NCL.
> I have a 2d-observation field in a rectangular grid and I wonder if there
> is any built-in NCL function that allows one to find the nearest grid
> observation poinr indexes (i,j) to any wrfout* (lon,lat) coordinates..
> Thanks in advance,
>                               Juan
>
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