Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Sunday, October 31, 2010

Meatballs with a Chance of Cloudspotting

While as a dad I enjoyed the art and humor in the picture book Cloudy With a Chance of Meatballs, I wasn't interested in going to the recent movie. But I had to watch some of it anyway, as a silent film, since it showed on the airliner during a flight back from Japan this summer.

The blog title refers to my distracted style of eating, say, if we are having Italian. If the sky-light is favorable and the clouds are mobilized, I'll excuse myself several times to peek out the window, sometimes to run outside with a camera. My urge toward cloudspotting is in its third year and shows no sign of abating. It began with collecting digital time-lapse movies of cloud formation.

Many cloudspotters dislike contrails because they can make the sky look like a poorly-scrubbed blackboard. Atmospheric studies during the airline-banned three-day period immediately after the 9-11 attacks did show a distinct difference in cloud formation over the continental US.

But they can have a beauty of their own. Here's a garden-variety contrail:

Sometimes contrails linger and spread out.

Next is a distrail, meaning where a jet cuts a slot. I've only seen this in low- and mid-level clouds. The reason that there are two parallel slots is that sequential jets on their landing approach were following the same track, but the cloud here, which looks like a stratus nebulosus, was moving from south to north so each jet cut a new slot.

If the air is just right, high-level contrails can create some spectacular loops and whorls as the contrails are caught in the wingtip vortices shed by wings and the tail empennage. I see these less than a dozen days a year. In my limited experience it's most likely early in the morning, when the stratosphere is extremely calm. It may more likely during the turnaround, a brief time of year when there is low windshear in the stratosphere - that's when NASA launches its ultra-high-altitude scientific balloons. (Here's a link to an article I wrote for Smithsonian Magazine about that facility's work.)

At any rate the air up there has to be near saturation or else the moisture (which is always in the form of ice crystals) will sublimate before something interesting happens. Here are two contrail-curiosity photos, the first a smoke-ring of sorts I caught a month ago:

Here's a string of contrail beads, from two winters ago, low on the horizon at sunrise. Like nearly all the coolest cloud displays, these last less than five minutes, so if you want to catch them keep a camera close to hand.

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