A torrent wind is fast enough to be visible, why?

Question

Air is invisible, but very fast air can show a contrail, like on a plane upper wing. Why?

i didn't mean artificial clouds, not the contrails left by the planes but the contrail that you can see on the upper part of the wings when the plane is descending fast.

Answer 1

Well, contrails are not actually visible air - they're basically artificial clouds, formed when water vapor in the airplane's exhaust condenses as it cools. But I suspect what you mean is the blurriness that you sometimes see, like in the afterburners of an F-16? Basically, it's not the speed of the air, but the temperature. Light travels at slightly different speeds depending on the temperature of the air (or other medium) it's traveling through. These slight variations cause light to distort by bending and rebending, similar to why a straw looks "broken if you look at it through the side of a glass of water.

Answer 2

The vapor above the wings is water condensed from the air by the sudden lowering of temperature that accompanies the reduced pressure over the wing (which incidentally provides the wing's lift). This generally occurs when the relative humidity is fairly high. The phenomenon is similar to the formation of a lenticular cloud (a stationary cloud of moving air) over a mountain top when humid air is driven rapidly upward. These frequently happen on the northwest coast of the USA where ocean-warmed air meets the Rockies. In both cases the cloud ends where the pressure is restored to a higher value.

Answer 3

In a torrent the density of the air is not steady and constant. It continously changing So the images behind the torrent gets refracted. Actually we are not seeing the air but the images behind the air

Answer 4

Condensation due to the low pressure.