Contrail facts for kids

Contrails are like thin, white clouds you sometimes see behind airplanes flying high in the sky. The word "contrail" is short for "condensation trail." They are made of tiny ice crystals. Airplanes create them either from their engine exhaust or sometimes from their wingtips.

Contrails

The contrail of a four-engined jet over Bristol, England

How Contrails Form

Contrails form in two main ways:

• Engine Exhaust: Jet engines release hot air that has a lot of water vapor. When this warm, moist air mixes with the very cold air high up in the atmosphere, the water vapor quickly turns into tiny ice crystals. This is similar to how your breath makes a "cloud" on a cold day.
• Wingtips: As an airplane flies, its wings create changes in air pressure. This drop in air pressure also causes the air to cool down a lot. When the air cools enough, the water vapor in it can turn into tiny water droplets or ice crystals, forming a contrail.

Contrails from engine exhaust usually last longer and are more stable. Wingtip contrails often disappear quickly because of the air turbulence behind the plane.

Contrails and Weather

Scientists have studied how contrails might affect our weather. In 1998, NASA scientists did an experiment. They flew a jet in circles off the coast of the United States. This created contrails that grew into a cirrus cloud covering a huge area. Satellite pictures have also shown that jet contrails from planes over New Mexico once formed a cloud covering 13,000 square miles (34,000 km²).

It was thought that in places with lots of air traffic, contrails could change the weather. They might reduce how much the sun heats the ground during the day. They could also trap heat at night, keeping it warmer.

A special chance to test this idea happened after September 11, 2001. Air travel in the United States was stopped for three days. During this time, measurements showed that without contrails, the difference between day and night temperatures was about 1 degree Celsius higher. This suggests that contrails can indeed affect local temperatures.

Images for kids

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  A Boeing 747 leaving a contrail

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  Contrails of a Boeing 747-400 from Qantas at 11,000 meters (36,000 feet)

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  A vintage P-40 Warhawk with propeller tip vortex condensation

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  MODIS tracking of contrails generated by air traffic over the southeastern United States

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  The sky above Würzburg without contrails after air travel disruption in 2010 (left) and with regular air traffic and the right conditions (right)

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  A distrail is the opposite of a contrail

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  Multiple contrails above Nova Scotia

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  Contrails formed due to two jets crossing over

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  Airliner contrails, some new, some old, dispersed by wind shear

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  A contrail over southwest Virginia

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  A contrail casting a shadow onto a lower cloud layer

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  Airplane contrail

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  Over the City of Culture of Galicia

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  Distrail – a narrow line of clearance produced by a passing airplane, here produced in a patch of thin cirrostratus.

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  Wiki Commons description page

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  Iridescent contrails from a Boeing 747, when the sun shines through a group of similarly sized water droplets at a relatively small angle

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  An Airbus A340 of Lufthansa produces contrails

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  Two USAF F-15s approaching Soviet MiG-29s

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  Contrails in front of the sun

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  Engine exhaust contrails behind an Airbus A340 from Swiss International Air Lines

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  B-17 bombers over Europe, 1944

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  USAAF 8th Air Force B-17s and their contrails

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  The unique Antonov 225 had distinctive sextuple vapor trails

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  Virga falling from contrail

See also

In Spanish: Estela de condensación para niños