Radar Problems

[MG Jennings]

Since last night, when viewing the national radar composite, many of the sites appear to have an expanding green colored clutter. When I click on a radar site, you can see the active weather but it is somewhat covered by the clutter. I use Stormlab with Allison House with level 3. I saw where Allison House needs updating. Although I use AH, I though I was still using the SL radar from NWS..Could this be the problem.....thanks

 

[Jeff Snyder]

Did the ground clutter appearance fade within a few hours after sunrise? If so, are you sure it wasn't the normal nocturnal expansion of ground and biological scatterers? After peak heating (usually mid-later afternoon), boundary layer mixing decreases and, eventually and typically, ceases. As this happens, near-surface stability increases, and, around dusk, bugs tend to come out. Together, there tends to be considerably greater ground clutter and non-meteorological scattering at night than during the day. I looked at some data from last night, but I didn't see anything terribly abnormal (though, again, I only looked at a couple of sites).

 

[MG Jennings]

I just checked the radar & it does seem to have cleared up somewhat during the day. I just have never seen this phenomenon previously. It only happens in the states in the middle of the country from Texas northward. Also, seems when I use the composite reflectivity mode there still remains a pretty substantial amount of clutter away from the radar. I did just check one site which has weather and the clutter actually overlays the rain signature, similar to a semi-transparent overlay. On the national composite loop it looks like a lime green clutter growing from the site.

Beats me!....Thanks for the opinion & I'll continue to monitor it.

 

[rdale]

That's a normal night-time occurrence.

 

[Todd Renshaw]

Can you show us a screen capture of what you're seeing?

 

[GPhillips]

What you are seeing is "radar blooming". This happens during the evening/overnight because of the inversion that sets up at low-levels in the atmosphere. This inversion results in the radar beam bending toward the surface of the earth, and so it stays in the atmospheric boundary layer for longer distances from the radar. This is called super-refraction of the radar beam. Since the beam shoots through the boundary layer for farther distances at night, the bugs, dust, aerosols, bats, birds, smoke particles that are frequent in the boundary layer at night, are detected farther away. It's most apparent during the warmer part of the year when such non-weather targets are more numerous.

A nice page that explains what atmospheric refraction of the radar beam is at

http://www.srh.noaa.gov/jetstream/doppler/beam_max.htm

 

[MG Jennings]

Thanks so much everyone for taking the time to assist me...it has all cleared up now. No doubt all of you are correct....I just have never seen it appear before....GPhillips, thanks for the article, I'll read it now.