[ncl-talk] Plotting Composite radar data -- how to?

[Dave Allured - NOAA Affiliate]

Barry, this file lacks the coordinate variables that are normally provided
in most published Netcdf data sets.  However, there appears to be almost
enough information in the global attributes to construct grid coordinates.
There are reference latitude and longitude, and the X and Y grid spacing.

The reference coordinates are ambiguous.  My guess is they are probably
grid center coordinates, but not sure.  With odd numbers for both X and Y
dimensions, that suggests that the center grid point (1000, 1000) is right
at (40N, 110W).

So just calculate X and Y coordinate vectors centered on the reference
coordinates, attach them to the data variable, then plot normally.  To
minimize precision loss, use *ispan* and divide by 100 as the final step,
because 0.01 step size is not exactly representable in floating point.
 (Not very important.)  E.g.:

      lats  = lat_center  + (double (ispan (-1000, 1000, 1)) / 100)
      lons = lon_center + (double (ispan (-1000, 1000, 1)) / 100)


On Thu, Sep 22, 2022 at 11:28 AM Barry Lynn via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Hello:
>
> I am wondering if there is a simple way to plot this radar data
> correctly on a grid.
>
> I can extract the radar data, no problem, but am wondering how to specify
> the lat/lon of the data.  Can it be obtained from the radar data itself?
>
> Thank you.
>
> Variable: b
>
> Type: file
>
> filename: 20120415-080000
>
> path: 20120415-080000.netcdf
>
>    file global attributes:
>
>       TypeName : mrefl_mosaic
>
>       DataType : LatLonHeightGrid
>
>       Time : 1334476800
>
>       FractionalTime :  0
>
>       MissingData : -999
>
>       RangeFolded : -1000
>
>       Latitude : 40
>
>       Longitude : -110
>
>       Height : 500
>
>       LatGridSpacing : 0.01
>
>       LonGridSpacing : 0.01
>
>       attributes :
>
>    dimensions:
>
>       Ht = 31
>
>       Lat = 2001
>
>       Lon = 2001
>
>    variables:
>
>       short mrefl_mosaic ( Ht, Lat, Lon )
>
>          Units : dBZ
>
>          Scale : 10
>
>
>       float Height ( Ht )
>
>          Units : Meters
> --
> Barry H. Lynn, Ph.D
> Senior Scientist, Lecturer,
> The Institute of Earth Sciences,
> The Hebrew University of Jerusalem,
> Givat Ram, Jerusalem 91904, Israel
> Tel: 972 547 231 170
> Fax: (972)-25662581
>
> Weather It Is, LTD
> Weather and Climate Focus
> https://weather-it-is.com <http://weather-it-is.com>
> Jerusalem, Israel
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> Cell: 054 7 231 170
> Int-IS: x972 2 930 9525
>
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