If you’ve ever seen a jet fly across the sky, you may have noticed that there is sometimes a thin white line behind it. These clouds are contrails, short for condensation trails.
According to Physic World magazine, when plane fly across a clear blue sky, it leaves behind a white streak across the sky. After a while, the track fades and disappear into thin air. They form a bit similarly to how the breath you exhale can condense into vapour on a cold day.
Aeroplanes engines burn hydrocarbons fuels so the combustion products are carbon dioxide and water. The exhaust leaving the engine is very hot so the water is in gaseous state: water vapour. As it come into contact with very cold air of -240 degree celsius at an altitude of 26,000 feets, it condenses into tiny droplets of water. The deposition lines are called contrails, and is like cirrus clouds.
Skywriters uses special airplanes which is equipped with different colours of oil and smoke machines. Oil is pimped into hot exhaust systems where it burns quickly and produces dense smoke. Pilots fly them carefully to create unique writings in the sky.
Wing lip vortices are formed due to difference in pressure between lower and upper wing; and tendency of air to move from high pressure to low pressure region. The associated vortices are visible due to subsequent drop in dew point.
Recent research has suggested that the ice clouds contained in contrails cause greenhouse effects and contribute to global warming as part of the insulating blanket of moisture and gases in the atmosphere.
Hi Researchers in this area seized on the opportunity presented on September 11 and 12 over the U.S. The complete cessation of commercial air traffic offered a control sky without contrails for use in quantifying the environmental effects of contrails.