This photograph shows many contrails in the sky near Sutherland, NE (November 2004).
Click on image for full size
Courtesy of Susan Gallagher
The white streaks you see coming off high-flying jet airplanes are called contrails, which is short for condensation trail. Contrails are clouds that form when water vapor condenses and freezes around small particles (aerosols) that exist in aircraft exhaust. The water vapor comes from the air around the plane and the exhaust of the aircraft.
Some contrails evaporate quickly while others stay in the sky for a long time after the airplane is gone. These contrails can become human-made cirrus clouds. Contrails last longer when there is a greater amount of water in the air; they last until the water in the clouds evaporates.
There are three types of contrails: short-lived, persistent non-spreading, and persistent spreading.
The study of contrails addresses important scientific questions, as they are clouds whose formation is a direct result of human activities. A change in the amount of high-level cloudiness resulting from contrails may impact our climate. Contrails can be seen over virtually all parts of the world as white streaks across the sky. This image shows widespread contrails over the southeastern United States.
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