[ncl-talk] Radar data plotting, no MAP_PROJ attribute

[Alexander Schaefer]

Ryan,

You might try looking here:

http://www.ncl.ucar.edu/Document/Graphics/overlays_on_map.shtml <http://www.ncl.ucar.edu/Document/Graphics/overlays_on_map.shtml>

Check out point 2 talking about lat2d and lon2d.

It might be as simple a fix as 

rd_plane at lat2d = rlat
rd_plane at lon2d = rlon

It should associate lat/lon point wise like you are looking for.

Cheers,
-Alex




> On Jul 20, 2016, at 3:31 PM, Ryan Connelly <rconne01 at gmail.com> wrote:
> 
> Hi Mary,
> 
> Thanks for getting back to me.  Sorry about the delay on my end.
> 
> printVarSummary of the rlat (or rlon) array shows
> 
> Variable: rlat
> Type: float
> Total Size: 131044 bytes
>             32761 values
> Number of Dimensions: 2
> Dimensions and sizes:	[y0 | 181] x [x0 | 181]
> Coordinates: 
>             y0: [-120..119.94]
>             x0: [-120..119.94]
> Number Of Attributes: 3
>   _FillValue :	41.94297
>   standard_name :	latitude
>   units :	degrees_north
> 
> 
> and for rd_plane shows
> 
> 
> Variable: rd_plane
> Type: float
> Total Size: 131044 bytes
>             32761 values
> Number of Dimensions: 2
> Dimensions and sizes:	[y0 | 181] x [x0 | 181]
> Coordinates: 
>             y0: [-120..119.94]
>             x0: [-120..119.94]
> Number Of Attributes: 12
>   z0 :	 2
>   time :	1424628563
>   grid_mapping :	grid_mapping_0
>   coordinates :	lon0 lat0
>   units :	dBZ
>   long_name :	radar_reflectivity
>   standard_name :	REF
>   _FillValue :	9.96921e+36
>   valid_max :	25.3757
>   valid_min :	-9.187451
> 
> printMinMax shows:
> 
> (0)	latitude: min=39.779   max=41.943
> (0)	longitude: min=-74.313   max=-71.4156
> 
> The values of rlat and rlon are the correct latitude and longitude values, but the trouble seems to be in matching the i,j'th point in rd_plane with the lat,lon contained in the i'th point of rlon and j'th point of rlat, so that the code can plot radar reflectivity in the correct place.
> 
> Thanks,
> Ryan
> 
> On Sun, Jul 10, 2016 at 11:53 PM, Mary Haley <haley at ucar.edu <mailto:haley at ucar.edu>> wrote:
> Hi Ryan,
> 
> You can't use wrf_xxxx functions to plot anything but WRF-ARW data.  These functions assume that you are using WRF files with names like "wrfout_d01_2008-09-28_00:00:00" which have a bunch of global attributes in them that define the native map projection of the WRF data. This is why you were getting an error about MAP_PROJ being undefined.  This is one of the required global attributes.
> 
> If you are trying to plot the data over a map, then you will need to examine your file and your data variable (rd_plane) to determine if it is also on some native map projection, or whether you need to provide lat/lon coordinates for plotting.  I then suggest using the gsn_csm_contour or gsn_csm_contour_map functions to generate just contours, or contours over a map.
> 
> Please see this page for some examples on how to plot data over a map using NCL:
> 
> http://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml <http://www.ncl.ucar.edu/Applications/plot_data_on_map.shtml>
> 
> You might also want to look at this page:
> 
> http://www.ncl.ucar.edu/Applications/radar.shtml <http://www.ncl.ucar.edu/Applications/radar.shtml>
> 
> 
> --Mary
> 
> 
> On Fri, Jul 8, 2016 at 4:35 PM, Ryan Connelly <rconne01 at gmail.com <mailto:rconne01 at gmail.com>> wrote:
> Hi,
> 
> I have Level II radar data in netcdf format (using radx and the steps outlined here: https://publish.illinois.edu/snesbitt/resources/radar-data-processing-with-radx/ <https://publish.illinois.edu/snesbitt/resources/radar-data-processing-with-radx/>).
> 
> I want to overlay it on a base map, in the same way I would with WRF data.  Here's a highly condensed version of what I have:
> 
> rf    = addfile(diri+fili,"r")
>        rd    = rf->REF(:,:,:,:)          ; float REF(time, z0, y0, x0) ; RHO, ZDR
> 
>        rd_plane = rd(0,0,:,:)
> 
>        contour =  gsn_csm_contour(wks,rd_plane,radres)
>        plot = wrf_map_overlays(rf,wks,(/contour/),radres,mpres)
> 
> I was just assuming the netcdf had location data packaged into it, but I get the error:
> 
> (0)	wrf_map: Error: no MAP_PROJ attribute in input file
> fatal:overlay: missing value as input, can't continue
> 
> I tried adding in a wrf file I had laying around and using it for map plotting, and while that got be a basemap, by radar data was obviously not matched geographically (it showed the KOKX RDA over New York City!).
> 
> Thanks,
> Ryan
> 
> -- 
> Ryan Connelly
> M.S. Student in Atmospheric Sciences, Stony Brook University
> B.S. in Meteorology with Minors in Mathematics and GIS, Valparaiso University
> rconne01 at gmail.com <mailto:rconne01 at gmail.com>
> ryan.connelly at stonybrook.edu <mailto:ryan.connelly at stonybrook.edu>
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> 
> 
> 
> 
> -- 
> Ryan Connelly
> M.S. Student in Atmospheric Sciences, Stony Brook University
> B.S. in Meteorology with Minors in Mathematics and GIS, Valparaiso University
> rconne01 at gmail.com <mailto:rconne01 at gmail.com>
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