Why do radars always show that bit of green around larger cities?

For some reason, the radar I use to check the weather always displays some green rain around Atlanta. I'm just curious why it does that, and why it sometimes stretches out further.

http://www.wunderground.com/radar/radblast.asp?ID=...

Might block that link, but it'll show what I'm talking about.

Is it always raining there? Is it pollution or something causing interference?

3 Answers

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  • Anonymous
    7 years ago
    Best Answer

    It is called ground clutter returns. This occurs when objects such as trees, terrain, buildings, birds, bats, or insects obstruct the radar beam. The beam bounces off these objects and returns to the doppler radar. This beam return shows up on the radar. The technology advancements of radar with the addition of dual polarization has made it easier to detect what exactly the radar beam is bouncing off of.

    Source(s): Storm spotter/chaser
  • TQ
    Lv 7
    7 years ago

    One thing for certain the green surrounding the radar site is not caused by the beam bouncing off bats...birds...dusts...trees...or buildings. Where do people come up with such nonsense?

    The green area is called 'anomalous propagation' aka 'ground clutter.'

    After the beam is emitted from the radome...it encounters a low-level temperature inversion where it's deflected toward the ground where it's deflected toward the inversion...over and over again. This effect is most common shortly before sunset and dissipates shortly after sunrise when the turbulent mixing resumes in the boundary layer.

    Source(s): Meteorologist.
  • Arasan
    Lv 7
    7 years ago

    Yes;they are called ground clutters.It is nothing but ground reflections of the radar beam.A portion of the radar beam(particularly lower portion of the beam) gets reflected from nearby objects like buildings and the echoes are seen in this way.They will always be present.If you lift the radar antenna by one or two degrees more,it will vanish.

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