Re: [ldm-users] High res Nexrad level 3 much noisier than low res?

  • To: Rob Dale <rdale@xxxxxxxxxxxx>
  • Subject: Re: [ldm-users] High res Nexrad level 3 much noisier than low res?
  • From: Pete Pokrandt <poker@xxxxxxxxxxxx>
  • Date: Wed, 02 Jan 2013 17:28:35 -0600
I thought about the sunset spikes and the timing of my email right after I sent it..

The other thing that occurred to me after I sent that is that since the high res products have a longer range (248 nmi vs 124 nmi), things like sunset spikes and other radial issues (like the Lincoln IL spike to the west) are longer and more noticeable than in the lower resolution images, just because they are longer.

Just saw a simlar comment/explanation in a gempak support email in the archives from 2010... Never mind, I guess..

Thanks though.
Pete


On 01/02/2013 05:15 PM, Rob Dale wrote:
There are many more radial solid lines (i.e. something like a building
is
blocking the beam in one direction, or interference with a neighboring
radar)
and also much more noise in general. The Lincoln, IL radar has a radial
line
almost due west pretty much all the time, and the Sioux Falls, SD radar
seems
to have many radial false echos - not a straight line, but lots of
smaller dots
along many of the radials.
I don't see any "more" bad data, it just is more evident due to the higher
resolution.

All of those "artifacts" are quite clearly in the raw data. For example,
L2 from KILX shows the blockage to the west. FSD is showing that
interference(?) pattern. Many of the other spikes are simply sunset
spikes. If you use a 4-bit NIDS viewer you will see the exact same
artifacts, they just might be harder to recognize due to the lower
resolution.

Not sure what, if anything can be done about it, but it's kind of a
bummer
that these higher resolution products have such poor quality control.
I think you are looking at it the wrong way... The 8-bit data is showing
more detail than 4-bit. That's a good thing.

   - ROb


--
Pete Pokrandt - Systems Programmer
UW-Madison Dept of Atmospheric and Oceanic Sciences
608-262-3086  - poker@xxxxxxxxxxxx



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