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

[Ryan Connelly]

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> 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
>
> You might also want to look at this page:
>
> http://www.ncl.ucar.edu/Applications/radar.shtml
>
>
> --Mary
>
>
> On Fri, Jul 8, 2016 at 4:35 PM, Ryan Connelly <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/
>> ).
>>
>> 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
>> ryan.connelly at stonybrook.edu
>>
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk at ucar.edu
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>


-- 
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
ryan.connelly at stonybrook.edu
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20160720/8f801650/attachment.html