Re: [python-users] MetPy NEXRAD Level 2 - Can get lat, lon out to use for plotting map?

• To: python-users@xxxxxxxxxxxxxxxx, Ryan Connelly <rconne01@xxxxxxxxx>
• Subject: Re: [python-users] MetPy NEXRAD Level 2 - Can get lat, lon out to use for plotting map?
• From: Kevin Goebbert <kevin.goebbert@xxxxxxxxx>
• Date: Tue, 25 Apr 2017 10:58:48 -0400

Hi Ryan!

There are a couple of directions you can go. As far as I know, there is not
lat/lon grid available in the nexrad files. However, you do have the
lat/lon of the radar itself. From there you can use that point to generate
the lat/lons from your x and y variables using pyproj. The x and y
variables are essentially in azimuthal equidistant projection so  you could
use something like,

def get_lonlat(x,y):
    from pyproj import Proj

    p = Proj(proj=‘aeqd', ellps='sphere',
             lon_0=nexrad_lon,
             lat_0=nexrad_lat)

    return p(x,y,inverse=True)

all you have to do is plug in the proper lon/lat value from the nexrad
file, then feed it the x and y values and it will return two arrays. The
call in a notebook might be

lon, lat = get_lon_lat(xlocs,ylocs)


Alternatively, you could use pyart, which now has the capability to plot
using Cartopy

http://arm-doe.github.io/pyart/dev/user_reference/generated/pyart.graph.RadarMapDisplayCartopy.html#pyart.graph.RadarMapDisplayCartopy

Easy install for pyart

conda install -c conda_forge arm_pyart

-Kevin

On 25 April 2017 at 8:05:35 AM, Ryan Connelly (rconne01@xxxxxxxxx) wrote:

Hi,

Using this code:
https://unidata.github.io/MetPy/examples/formats/NEXRAD_Level_2_File.html#sphx-glr-examples-formats-nexrad-level-2-file-py

Ideally, I should be able to just extract a lat and a lon variable from the
file, except that I don't know if they exist, and if they do, what their
names are.

>From there, I'd like to plot the georeferenced data over a base map using
CartoPy.  Is this possible?  (I just happen to already have some shapefiles
on hand that I want to use that I know CartoPy can read in.)

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@xxxxxxxxx
ryan.connelly@xxxxxxxxxxxxxx
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-- 
Kevin Goebbert, Ph.D.
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• References:
  • [python-users] MetPy NEXRAD Level 2 - Can get lat, lon out to use for plotting map?
    • From: Ryan Connelly