Vapour trails why

When we got down into the bottom Mac turned aside to the deep-worn trail and glanced sharply down at the ruts. She had been walking alone with her arms hanging limp, letting her white skirts trail along the dewy path. Top Definitions Quiz Examples vapour trail. New Word List Word List. Save This Word! We could talk until we're blue in the face about this quiz on words for the color "blue," but we think you should take the quiz and find out if you're a whiz at these colorful terms.

The combustion of hydrocarbon fuels in a jet engine releases water as by-product, ejected in gaseous form as water vapour in a stream behind the aircraft.

This moisture raises the relative humidity in the wake, and if conditions are right, the air in the affected zone may reach its saturation point; if it does, condensation takes place, water droplets form, and the result is familiar elongated tube of cloud.

Saturation, and hence the exhaust trails, can normally occur only when the temperature of the outside air is below a certain critical value, depending on the altitude. At the cruising height for modern aircraft, 35, feet or thereabouts, this temperature is about C; at sea level it is around We therefore never see condensation trails in these parts when a plane is taking off or landing, because the surroundings are not cold enough.

As you may have noticed, condensation trails vary greatly in persistence. If the air is calm aloft, and the relatively humidity in the vicinity is high, the trail tends to persist for a long time, because the atmosphere is reluctant to re-absorb the suspended water droplets. If on the other hand, the winds are strong and the moisture content low, then dry surrounding air vigorously infiltrates the cloud, facilitates evaporation, and the contrail breaks up and dissipates with great rapidity.

The type of aircraft has an impact, too. The resulting clouds resemble long strings over the ocean. These are often much wider than contrails so they can often be seen on satellite pictures of the earth. Contrails or condensation trails. Height of base: above 20, ft.

Precipitation: None What are contrails? Contrails are long thin lines of cloud, usually seen behind an aircraft. How do contrails form? What weather is associated with contrails?

How do we categorise contrails? You might also like. Fogs which are mainly composed of water droplets are generally classified according to the physical process which produces saturation or near-saturation of the air. Read more. Altostratus evolves as a thin layer from a gradually thickening veil of cirrostratus and is usually grey or blue, with very few features.