Science & TechFact

Contrails are clouds made of exhaust water.

Burning kerosene produces water vapour. At 10 kilometres altitude it is about minus 50 degrees; the hot vapour cools within seconds, condenses on soot particles and freezes into ice crystals. If the surrounding air is dry, the trail evaporates immediately. If it is humid, it lingers for hours and can spread into a cirrus cloud.

Useful: Long, persistent trails indicate humid air aloft, often a sign that weather is about to change.

Source: en.wikipedia.org

Luftfahrt Physik Wetter

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