Vapor Trails from airplanes?

Question

At what height do vapor trails appear? And what height above that do they disappear?

Answer 1

they don't disappear until about 7,000 but only appear at at least 9,000

Answer 2

Contrails or vapor trails are condensation trails and artificial cirrus clouds made by the exhaust of aircraft engines or wingtip vortices which precipitate a stream of tiny ice crystals in moist, frigid upper air. Being composed of water, the visible white streams are not air pollution. However, vapour trails or contrails generated by engine exhaust are inevitably linked with typical fuel combustion pollutants.

Condensation from engine exhaust

The main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can push the water content of the air past saturation point. The vapor then condenses into tiny water droplets and/or deposits into ice particles . These millions of tiny water droplets and/or ice crystals form the vapour trail or contrails. The energy drop (and therefore, time and distance) the vapor needs to condense accounts for the contrail forming some way behind the aircraft's engines. The majority of the cloud content comes from water trapped in the surrounding air.[citation needed] At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly turn to ice crystals. Exhaust vapour trails or contrails usually occur at above 26,000 feet. where the temperature is below -40°C (-40°F).



The contrails of a four-engined jet airliner over London, England

Condensation from decreases in pressure

Main article: wingtip vortices

The wings of an aircraft cause a drop in air pressure in the vicinity of the wing. This brings with it a drop in temperature, which can cause water to condense out of the air and form a vapour trail or contrail. This effect (the Prandtl-Glauert singularity), is more common on humid days, and can be seen on fighter jets performing high energy maneuvers, during shuttle launches, on the expanding surface "bubble" of nuclear explosions, or on airliners during takeoff and landing. Additionally, the area around a turbo-fan intake will be at a lower pressure than the surrounding air, and may result in a condensation fog forming there during high power settings.

These effects are compounded with the other explanation of contrails, which is the water vapor produced by the combustion of jet fuel. High altitude contrails are seen directly behind the one or two jets, and with aircraft with four jets, such as the Boeing 747, there are four contrails. The vapor trails caused by the first mentioned effect are usually seen at low altitude where the ambient humidity is higher, and they follow the wings rather that the jet engines. Vapour trails or contrails and climate

Vapour trails or contrails, by affecting the Earth's radiation balance, act as a radiative forcing. Studies have found that vapour trails or contrails trap outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) at a greater rate than they reflect incoming solar radiation (negative radiative forcing). Therefore, the overall net effect of contrails is positive, i.e. a warming.[2] However, the effect varies daily and annually, and overall the magnitude of the forcing is not well known: globally (for 1992 air traffic conditions), values range from 3.5 mW/m² to 17 mW/m². Other studies have determined that night flights are most responsible for the warming effect: while accounting for only 25% of daily air traffic, they contribute 60 to 80% of contrail radiative forcing. Similarly, winter flights account for only 22% of annual air traffic, but contribute half of the annual mean radiative forcing.September 11, 2001 climate impact study

It had been hypothesized that contrails may affect the weather, reducing solar heating during the day and radiation of heat during the night by increasing the albedo. The suspension of air travel for three days in the United States after September 11, 2001 provided an opportunity to test this hypothesis. Measurements did show that without contrails the local diurnal temperature range (difference of day and night temperatures) was about 1 degree Celsius higher than immediately before;however, it has also been suggested that this was due to unusually clear weather during the period.

Distrails

Where an aircraft passes through a cloud, it can clear a path through it; this is known as a distrail.

Answer 3

Exhaust vapour trails or contrails usually occur at above 26,000 feet. where the temperature is below -40°C (-40°F)

Jets dont usualy fly much higher than about 37,000 feet .. so you'd see them between 26,000 ft and 37,000 ft

smaller business jets sometimes operate up to 45000 feet and in the case of Concorde it went as high as 51000

i would imagine you would be able to see contrails  up to those altitudes

The main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can push the water content of the air past saturation point. The vapor then condenses into tiny water droplets and/or deposits into ice particles . These millions of tiny water droplets and/or ice crystals form the vapour trail or contrails. The energy drop (and therefore, time and distance) the vapor needs to condense accounts for the contrail forming some way behind the aircraft's engines. The majority of the cloud content comes from water trapped in the surrounding air.[citation needed] At high altitudes, supercooled water vapor requires a trigger to encourage deposition or condensation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly turn to ice crystals. Exhaust vapour trails or contrails usually occur at above 26,000 feet. where the temperature is below -40°C (-40°F).[1]

Answer 4

Water that is condensed is liquid or solid, not vapor.

Answer 5

Caroline..the short answer is...veryvery hot jet exhaust entering a veryvery cold air mass causes a condensation trail.

Just like a hot shower in a cold bathroom.