Wednesday, 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 turn...at least not for long.

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