What kind of smog those airplanes release into my clear blue sky?

Question

I often see small airplanes across the clear blue sky leaving sort of smoke/fog forming a line spliting the air. The airplanes go back and forth and in time the sky is not as beautiful as it was with those smog spreading all over.

Are they trying to create clouds in dry weather to induce rain? For what its worth I hate see my clear blue sky ruined.

Answer 1

Condensation trails or contrails often appear behind aeroplanes. During the Second World War, bomber and fighter pilots noticed that they left contrails at some levels but not at others. On a day when contrails were happening, the safest level to fly was just below the level at which they occurred. Any enemy aircraft higher up would be leaving a trail and would be easy to see. This led to a study of contrails and a method of predicting the level at which they would occur was devised.

There are two different types of condensation trail. If you are in an aeroplane on a day with showers around, look at the wings as the plane descends. You will see a trail of what looks like grey smoke streaming from the end of the wing. The motion of air across the wing creates a vortex at the wing tip. The drop in pressure across the vortex is enough, on a humid day, to cause the water vapour to condense into cloud droplets and this is seen streaming from the wing tip. These condensation trails evaporate quickly behind the plane.

The trails we see high in the sky are made by the engines, not vortices at the wing tips. When fuel is burnt, water vapour is produced. We can see this coming from car exhausts on frosty mornings. The water vapour in the hot exhaust gases condenses in the cold air. The same thing happens with aircraft exhausts and the condensed water droplets leave a visible trail behind the aircraft. If the air is dry, the water droplets quickly evaporate and the contrail disappears. If the air is moist, the contrail can last a few minutes before it evaporates.

Water vapour will not spontaneously condense into water droplets. The water has to condense onto something. These are called condensation nuclei. Salt and dust particles are common nuclei. Smoke particles are also good nuclei. If the air is very clean and lacking in condensation nuclei it can become supersaturated. There is plenty of water vapour in the air but it can't condense. An aeroplane flies through this supersaturated air pumping out not only water vapour but also billions of smoke particles onto which the water vapour can condense. A condensation trail forms and stays for a long time. Sometimes these trails can spread out to form a sheet of cloud across the sky.

If you want some amusement, you should look up "chemtrails" on your favourite search engine. There is a major conspiracy theory that condensation trails are attempts by the government to poison the population. This is not the case and never has been.

A rare form of trail is the dissipation trail or distrail. As a plane flies through high-level cloud, the heat from the engines evaporates the cloud cutting a clear line through the cloud. Distrails can be confused with the shadows of contrails. A contrail above a thin layer of cloud will cast a shadow on the cloud layer leaving an odd-looking dark line. It is particularly strange if the cloud layer cannot be easily seen.

Answer 2

A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scattered out and away from the line of sight.

Answer 3

Its jet exhaust or contrails. jet exhaust is dark and usually expelled on takeoff. What you are seeing on high are called Contrails. Contrails are water vapor that is formed by the water in the upper atmosphere as an aircrafts interupts it. They are water or vapor trails.

Answer 4

Who says it is 'your' clear blue sky? its everyones to enjoy... sorry i dont know what could be ruining the sky after the planes go through. Maybe it is burn off engine fuel or gases.

Answer 5

The CO2 and CO are both invisible gases - what you are seeing that streaks your clear, blue sky is almost entirely water vapor - same as the clouds.

Answer 6

One explanation could be, Chemtrails, search the term, for more information on what is released.

Answer 7

It not smog, they just dumping the Toilet Holding Tank.

Answer 8

the smog they leave behind is called chemtrails

Answer 9

a Con (Condensation) trail http://en.wikipedia.org/wiki/Contrail