|Author, Joe Thomissen|
And now, an “artificial” cloud: Contrails
We used to call them jet trails. The thin lines across the brilliant, blue sky, evidence of the flight of an airliner. Sometimes you’ll see several, crisscrossing one another. I never really thought of these as being actual clouds. But they are.
How are contrails formed? Jet engines emit exhaust that contains water vapor. Above 26,000 feet where the temperature is usually below -40 °F, condensation occurs quickly. Ice crystals form and your vapor trail is created.
Contrails can also be triggered by changes in air pressure, (wingtip vortices) in lower altitudes, when the jets are traveling at slower rates of speed. They trail behind the wingtips and wing flaps rather than the engines.
Contrails have an opposite effect called Distrails, which looks like a tunnel through existing clouds. It is the path of the jet, as shown in the picture below.
I would like to note here that there is some concern about the longterm consequences of contrails and chemtrails. You can read more about this aspect at http://www.pbs.org/wgbh/nova/space/contrail-effect.html.
|Author, Brocken Inaglory|