August 8, 2012

Pic: Radar Attenuation

I took this picture on Sunday afternoon while descending on the arrival to Ronald Reagan Washington National Airport.  In the picture, I'm on an ATC assigned vector for spacing with the aircraft ahead.

When using airborne radar, attenuation is a term regularly used to describe what you see here.  The green and yellow return standing alone on the left side of the screen does not appear to be especially large or dangerous.  But it is attenuating and the radar screen tells me nothing about what lies behind.  By tilting the radar beam down toward the ground, I was able to "paint" the ground at about 50 miles in front of the aircraft.  The green, yellow and red arc of color in the picture is the ground, not weather.  However, as you can see, the ground is not painting behind the storm.  There was enough moisture in this storm that my radar was not able to penetrate through the storm and paint what was on the other side.  There might be nothing there at all...or a level 5 thunderstorm might be lying in wait.

In my case, we never went anywhere near the storm.  But if I had been assigned a 030 heading, I would not have accepted the least not for long.


  1. great blog ever for information about airlines i personally like it very much,your work is very impressive and information is also fantastic,true and of luck!
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  2. I agree, great blog!

    What would ATC do next - would they clear you direct to one of your waypoints when the spacing was suitable or just continue to vector you to an approach fix (or whatever they feel like on the day given the traffic)?

    Keep up the great work.

    Dave from the UK

  3. Hi Dave, thanks for the comment. Usually ATC will clear us direct to another fix once they have the spacing they need. They could have vectored our flight to intercept an approach course, but in this case, we were still a significant distance from the approach, so we were cleared direct to another fix on the arrival.

  4. Thank you for this very useful information. Hopefully it will help lead to other adoptions.
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  5. Amazing information.

    I was watching Discovery and they used to claim that with doppler ground radar can penetrate through much of storms/moisture - perhaps something can be beamed up from ground to the airplane

    .... hmmmm I might be on something here?