Jenn Stroud Rossmann, an assistant professor of engineering at Harvey Mudd College, provides an explanation
Jets leave white trails, or contrails, in their wakes for the same reason you can sometimes see your breath. The hot, humid exhaust from jet engines mixes with the atmosphere, which at high altitude is of much lower vapor pressure and temperature than the exhaust gas. The water vapor contained in the jet exhaust condenses and may freeze, and this mixing process forms a cloud very similar to the one your hot breath makes on a cold day.
Jet engine exhaust contains carbon dioxide, oxides of sulfur and nitrogen, unburned fuel, soot and metal particles, as well as water vapor. The soot provides condensation sites for the water vapor. Any particles present in the air provide additional sites.
Depending on a plane's altitude, and the temperature and humidity of the atmosphere, contrails may vary in their thickness, extent and duration. The nature and persistence of jet contrails can be used to predict the weather. A thin, short-lived contrail indicates low-humidity air at high altitude, a sign of fair weather, whereas a thick, long-lasting contrail reflects humid air at high altitudes and can be an early indicator of a storm.
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The mixing gases contained in the contrail rotate with respect to the ambient air. These regions of rotating flow are called vortices. (Any sharp surface, such as the tip of a wing, can cause vortical flow in its wake if it is sufficiently large or the flow is sufficiently fast.) On occasion, these trailing vortices may interact with one another.
In one well-known example of this fact, the Crow Instability causes the vortices to develop symmetric sinusoidal oscillations and eventually to merge and form vortex rings behind the jet. This instability can be triggered by turbulence in the surrounding air or by local variation in air temperature or density, which may itself be the result of the stratification of the atmosphere. When the contrails are visible and strong, it is possible to see the white streaks become wavy and then leave rings floating high in the sky, like smoke rings from a giant cigar.
Recent research has suggested that the ice clouds contained in contrails cause greenhouse effects and contribute to global warming as part of the insulating blanket of moisture and gases in the atmosphere. Researchers in this area seized on the opportunity presented on September 11 and 12 over the U.S. The complete cessation of commercial air traffic offered a control sky without contrails for use in quantifying the environmental effects of contrails.
Contrails (/ˈkɒntreɪlz/; short for "condensation trails") or vapor trails are line-shaped clouds produced by aircraft engine exhaust or changes in air pressure, typically at aircraft cruising altitudes several miles above the Earth's surface.
, short for condensation trails. Water vapor is one of the byproducts of jet fuel combustion and will turn into ice crystals
ice crystals
Ice crystals are solid ice in symmetrical shapes including hexagonal columns, hexagonal plates, and dendritic crystals. Ice crystals are responsible for various atmospheric optic displays and cloud formations.
in the cold air at the high elevations where jet airplanes fly. Those ice crystals create a cloud (the contrail), which does not pose any public health risk.
It's the water vapour. They create the white trails left by the aeroplanes we see in the sky. However, when and why aircrafts leave vapour trails is fascinating. When an aeroplane is in the air, the engines produce and release a sizable amount of water in the form of water vapour out the back.
Often, aircraft appear to be at the same level with one causing a contrail and the other not. However, the regions of humid air that cause the contrails are known to be wide but shallow. A difference in flight level of 1,000 feet is enough for one aircraft to cause a contrail and the other not.
A study that looked at aviation's contribution to climate change between 2000 and 2018 concluded that contrails create 57% of the sector's warming impact, significantly more than the CO2 emissions from burning fuel. They do so by trapping heat that would otherwise be released into space.
On some occasions it's possible to see two aeroplanes flying at the same altitude but only one of them generates contrails or condensation tails. Why is this? It's because of engine efficiency.
Contrails, or condensation trails, are essentially human-made clouds; they are trails of condensed water vapor created by jet engines, according to the National Weather Service. We most commonly see them behind planes at cruising altitude, but they can also be emitted by rockets.
They may not be chemtrails, but contrails can affect our climate via radiative forcing, disrupting the balance between the sun's incoming solar radiation and the heat being emitted from the Earth's surface. In other words, persistent contrail clouds can trap heat in the atmosphere.
Contrails last longer when there is a greater amount of water in the air; when all of the water in the clouds evaporates the contrail disappears. There are three types of contrails: short-lived, persistent non-spreading, and persistent spreading.
Key Takeaways. Airplanes may need to dump fuel before landing to reduce weight in emergencies or due to maintenance issues. Not all aircraft are equipped with fuel-dumping systems; typically, only larger, wide-body planes have this capability, as required by the FAA.
Older military aircraft like the B-52 and C-130 can leave a black smoke exhaust even at cruising altitude, while aircraft like the KC-135R with new engines produce an invisible exhaust plume.
Contrails, like cirrus clouds and unlike thicker, lower-altitude clouds, can allow a considerable amount of solar radiation to penetrate to the Earth's surface, warming the planet.
"The way to avoid the contrail is to descend a little bit, think like 2,000 feet, 4,000 feet," Blickstein said. During 70 test flights from January 2023 to June 2023, pilots used the data to make the slight altitude adjustments.
While most aircraft can function normally after being struck, sometimes pilots may decide to make an emergency landing if displays or systems have been affected by the strike. Lightning typically hits the plane's extremities, like the wing tip or the nose of the plane, with the charge exiting from another extremity.
A jet contrail is only moving with the upper air mass and would be seen at night only under certain moonlight conditions or just before or after sunrise/sunset.
The white trails what you see when a jet flies in the sky are actually some sort of ice crystals, which may sometimes even persist for hours and span across miles wide! Sometimes these trails are so short-lived that we hardly get to see them. These trails are called contrails (short for “condensation trails”).
Scientists disagree about how much; estimates of contrail's impact range from 8 percent to 57 percent of aviation's total warming effect, with huge margins of error. But some researchers point out that, even at the lower end of the range of estimates, contrails still have a meaningful warming effect.
Jets leave white trails, or contrails, in their wakes for the same reason you can sometimes see your breath. The hot, humid exhaust from jet engines mixes with the atmosphere, which at high altitude is of much lower vapor pressure and temperature than the exhaust gas.
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