Rufford, Lancashire, Royaume-Uni. 21 janvier, 2017. & Froid tôt le matin brumeux à Rufford Marina, sur la Leeds Liverpool canal, comme le soleil levant met en évidence des traînées de vapeur d'aéronefs soulignant la route vers l'aéroport de Manchester. Credit : Cernan Elias/Alamy Live News
3600 x 2400 px | 30,5 x 20,3 cm | 12 x 8 inches | 300dpi
Date de la prise de vue:
21 janvier 2017
Lieu:
Rufford, Lancashire, UK
Informations supplémentaires:
Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.
A contrail will form behind a jet if, as exhaust gases cool and mix with surrounding air, the humidity is high enough and the temperature low enough for liquid water to condense. The air needs to be supersaturated and the temperature generally below -40°F, something that typically occurs only in the upper troposphere, the atmospheric layer several miles up where airliners cruise. Under those conditions, water vapor from the jet's exhaust and secondarily from the atmosphere condenses into water droplets. Within a few tens of feet behind the aircraft, these droplets freeze into the snow-white particles that bring the contrail to life. How long a newly formed condensation trail sticks around depends on the ambient humidity. If humidity is low, contrails will rapidly dissipate, looking like a comet's tail. The ice particles sublimate—meaning go straight from ice to vapor—and you're back to blue sky. If humidity is high, however, contrails can persist—and those are the ones that trouble climatologists. If conditions are right, newly formed contrails will begin feeding off surrounding water vapor. Like vaporous cancers, they start growing and spreading. In time, they can expand horizontally to such an extent that they become indistinguishable from cirrus clouds, those thin, diaphanous sheets often seen way up high. These artificial cirrus clouds can last for many hours, and the amount of sky they end up covering can be astonishing. One study showed that contrails from just six aircraft expanded to shroud some 7, 700 square miles.
