Condensation and dissipation trails

Contrails are clouds that form on the trail of an airplane at high altitudes when the atmosphere at flight level is cold and humid enough, and the air temperature is low enough to make the water vapor freezes instantly, forming a trail of ice crystals.

When newly formed, they look like bright white scratches; but after a short while they may have hanging lumps (mammatus) in the shape of inverted mushrooms. Often the existence of these trails is short, but particularly when Cirrus or Cirrostratus is present, they may persist for several hours.

Persistent tracks widen progressively and often turn into large fuzzy or fibrous banks, having the appearance of Cirrus or Cirrocumulus or Cirrostratus banks; Indeed, it is sometimes very difficult to distinguish between the clouds of these genres and the trails of ancient formation.

The main factor influencing the formation of condensation traces is the cooling of the flow gases which, as a result of the combustion of the fuel, have a strong water vapor content. Fleeting trails sometimes form as a result of air expansion at the ends of the propeller blades and wings.

Condensation trails have no effect on aviation in general, but in wartime their prediction and location are extremely important, as they denounce the presence of enemy aircraft invading a territory.

There is also the case where planes pass through a cloud layer and dissipate part of it, having an effect contrary to the vapor trail, ie a "clear corridor" (dissipation trail or distrail) in the middle of Very rarely, a distrail can turn into a cloud hole: a large elliptical hole in Altocumulus clouds, with a virgin in the middle (the fallstreak holes).