3-D Radar Image of Military Chaff

Dec 9, 2011; 11:18 AM ET

The Southeast U.S. has been plagued the past couple days by “military chaff” — groupings of millions of tiny fibers released by aircraft. This has been going on ever since radar was invented (in fact it can be a way to disrupt foreign aviation radar). You see it show up during clear weather every week or two, and since I’ve blogged about radar anomalies before, I’m surprised to realize that I haven’t talked about this one. Here’s a radar shot from southern Georgia and northern Florida yesterday afternoon, overlaid onto a 3-D radar image:

You can see that the chaff yesterday formed a very consistent “tube” in the atmosphere, extending from the surface up to about 12,000 feet. This is one way that meteorologists can identify it — because convective processes in the atmosphere produce rain, raindrops rarely appear this smooth and consistent. The more obvious way, of course, is to check the visible satellite — no clouds, no rain. Here’s a wider angle of what it looked like on radar:

What is chaff? GlobalSecurity.Org says simply “Chaff consists of small fibers that reflect radar signals and, when dispensed in large quantities from aircraft, form a cloud that temporarily hides the aircraft from radar detection.” Could it harm the environment? Releasing a bunch of aluminum and/or glass into the atmosphere doesn’t sound like a great idea, but that website uses words like “unidentified / not significant concerns / extremely isolated / few effects / not likely / remote” to describe any harmful effects. Their point is, the percentage of the atmosphere or earth (when it falls) is extremely small. I expect environmental groups would disagree.