Artifacts Above RHI Plot

[mgrover1]

Transferred over from #1166

I found another data oddness. If you need me to submit this formally via
github, I'll do that. If not, here's the story.

We're collecting a different kind of rhi volume that has 12 widely-spaced
azimuths that range from 0 to 360. They all plot up nicely except the 270
deg azimuth scan which has some artifacts above the radar. I used your
code snippet to do the plotting and added a couple things so I could tell
one plot from the next.

I thought it might be the cfradial file but the NCAR CIDD software displays
these 270 deg angle rhi's without any artifacts. See the image called
'spol.202206030411.rhi_270_cidd.png'.

Everything is attached. Let me know if you have any thoughts. You'll
probably need to take a look through this so I don't expect to talk about
it tonight. Just take your time and let me know what you find. If we need
to chat at that point, we can set something up.

Thanks for your help. I really appreciate it especially during this field
work.

Stacy

[mgrover1]

@srbrodzik coming back to this - it looks like it is a data quality issue.

There are some parts of the 270 degree RHI that have not been flagged to be as "antenna transition" (specifically the last radials)

Using the following manually added in the missing transition flags, but without doing this, there is a "rogue radial" in the top left of the plot causing the issues.

Before fixing the transition data:

After fixing the transition data:

And here was the code I used to correct it:

import pyart
import matplotlib.pyplot as plt
import numpy as np

# Read in the data and specify rhi scan type
radar = pyart.io.read("cfrad.20220603_040943.316_to_20220603_041149.938_SPOL_PrecipRhi2_RHI.nc")
radar.scan_type = 'rhi'

# Extract the 270 degree rhi which is where the issue is at
subset = radar.extract_sweeps([8])

# Pull out the transition data
trans = subset.antenna_transition["data"]

# Make sure the last four radials are excluded flagged as in transition (1 = in transition)
trans[-4:]  = [1, 1, 1, 1]

# Assign the new values back to the radar
subset.antenna_transition["data"] = trans

# Plot the corrected data
cmap_dict = {"DBZ": "pyart_HomeyerRainbow",
             "VEL": "pyart_balance",
             "ZDR": "pyart_Carbone42",
             "RHOHV": "pyart_Carbone42",
             "KDP": "pyart_Carbone42",
             "PHIDP": "pyart_Carbone42",}

display = pyart.graph.RadarDisplay(subset)
for sweep in range(subset.nsweeps):
    for field in list(cmap_dict.keys()):
        display.plot_rhi(field, sweep, cmap=cmap_dict[field])
        plt.show()
        plt.close()