Contrail
Contrails | |
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Precipitation | No |
Contrails (
Depending on the temperature and humidity at the altitude where the contrails form, they may be visible for only a few seconds or minutes, or may persist for hours and spread to be several miles wide, eventually resembling natural
Condensation trails as a result of engine exhaust
Engine exhaust is predominantly made up of water and carbon dioxide, the combustion products of hydrocarbon fuels. Many other chemical byproducts of incomplete hydrocarbon fuel combustion, including
A 2013–2014 study jointly supported by NASA, the German aerospace center DLR, and Canada's National Research Council NRC, determined that biofuels could reduce contrail generation. This reduction was explained by demonstrating that biofuels produce fewer soot particles, which are the nuclei around which the ice crystals form. The tests were performed by flying a DC-8 at cruising altitude with a sample-gathering aircraft flying in trail. In these samples, the contrail-producing soot particle count was reduced by 50 to 70 percent, using a 50% blend of conventional Jet A1 fuel and HEFA (hydroprocessed esters and fatty acids) biofuel produced from camelina.[8][9][10]
Condensation from decreases in pressure
As a wing generates
The visible cores of wingtip vortices contrast with the other major type of contrails which are caused by the combustion of fuel. Contrails produced from jet engine exhaust are seen at high altitude, directly behind each engine. By contrast, the visible cores of wingtip vortices are usually seen only at low altitude where the aircraft is travelling slowly after takeoff or before landing, and where the ambient humidity is higher; they trail behind the wingtips and wing flaps rather than behind the engines.
At high-thrust settings the fan blades at the intake of a turbofan engine reach transonic speeds, causing a sudden drop in air pressure. This creates the condensation fog (inside the intake) which is often observed by air travelers during takeoff.
The tips of rotating surfaces (such as propellers and rotors) sometimes produce visible contrails.[11]
In firearms, a vapor trail is sometimes observed when firing under rare conditions due to changes in air pressure around the bullet.[12][13] A vapor trail from a bullet is observable from any direction.[12] Vapor trail should not be confused with bullet trace, which is a much more common phenomenon (and is usually only observable directly from behind the shooter).[12][14]
Impacts on climate
In general, aircraft contrails are believed to trap
Contrail cirrus may be air traffic's largest radiative forcing component, larger than all CO2 accumulated from aviation, and could triple from a 2006 baseline to 160–180 mW/m2 by 2050 without intervention.[17][18] For comparison, the total radiative forcing from human activities amounted to 2.72 W/m2 (with a range between 1.96 and 3.48W/m2) in 2019, and the increase from 2011 to 2019 alone amounted to 0.34W/m2.[19] Contrail effects differ a lot depending on when they are formed, as they decrease the daytime temperature and increase the nighttime temperature, reducing their difference.[20] In 2006, it was estimated that night flights contribute 60 to 80% of contrail radiative forcing while accounting for 25% of daily air traffic, and winter flights contribute half of the annual mean radiative forcing while accounting for 22% of annual air traffic.[21]
Starting from the 1990s, it was suggested that contrails during daytime have a strong cooling effect, and when combined with the warming from night-time flights, this would lead to a substantial
In 2011, there has been a study of British meteorological records taken during
Head-on contrails
A contrail from an airplane flying towards the observer can appear to be generated by an object moving vertically.[35][36] On 8 November 2010 in the US state of California, a contrail of this type gained media attention as a "mystery missile" that could not be explained by U.S. military and aviation authorities,[37] and its explanation as a contrail[35][36][38][39] took more than 24 hours to become accepted by U.S. media and military institutions.[40]
Distrails
Where an aircraft passes through a cloud, it can disperse the cloud in its path. This is known as a distrail (short for "dissipation trail"). The plane's warm engine exhaust and enhanced vertical mixing in the aircraft's wake can cause existing cloud droplets to evaporate. If the cloud is sufficiently thin, such processes can yield a cloud-free corridor in an otherwise solid cloud layer.
Clouds form when invisible water vapor (H2O in gas phase) condenses into microscopic water droplets (H2O in liquid phase) or into microscopic ice crystals (H2O in solid phase). This may happen when air with a high proportion of gaseous water cools. A distrail forms when the heat of engine exhaust evaporates the liquid water droplets in a cloud, turning them back into invisible, gaseous water vapor. Distrails also may arise as a result of enhanced mixing (entrainment of) drier air immediately above or below a thin cloud layer following passage of an aircraft through the cloud, as shown in the second image below:
See also
- Chemtrail conspiracy theory
- Cirrus cloud
- Cloud chamber – particle detector that works on similar principle
- Environmental impact of aviation
- Fallstreak hole
- Global dimming
- Ship tracks
- Skywriting
- Space jellyfish
- Twomey effect
References
- ^ a b c "Aircraft Contrails Factsheet" (PDF). FAA.Gov. Archived (PDF) from the original on 28 September 2006. Retrieved 10 September 2023.
- ^ "vapour trail". Encyclopædia Britannica. Encyclopædia Britannica Inc. Retrieved 17 April 2012.
- ^ a b Sutherland, Scott (23 March 2017). "Cloud Atlas leaps into 21st century with 12 new cloud types". The Weather Network. Pelmorex Media. Retrieved 24 March 2017.
- ^ "Cirrus Aviaticus – Cirrus – Names of Clouds". namesofclouds.com. Retrieved 13 October 2021.
- ^ Timperley, Jocelyn. "The fastest ways aviation could cut emissions". www.bbc.com. Retrieved 11 June 2021.
- S2CID 30595016.
- ^ "Contrail Education – FAQ". nasa.gov. Archived from the original on 8 April 2016.
- ^ "The Week in Technology". Aviation Week & Space Technology. 20–24 March 2017. Paper published in Nature, Rich Moore & Hans Schlager, authors.
- ^ Sean Broderick (24 December 2017). "Biofuels Could Reduce Contrail Formation, Research Finds". Retrieved 13 October 2021.
- (PDF) from the original on 27 April 2019.
- ^ "Photos from the field". Archived 16 July 2014 at the Wayback Machine Vertical Magazine, April/May 2014, p. 39. Accessed: 8 July 2014.
- ^ a b c Vapor trail and Bullet trace Sniper Country accessed 13 October 2021
- ^ Vapor Trail vs Bullet Trace YouTube accessed 13 October 2021
- ^ Language Lessons: TRACE Breach Bang Clear accessed 13 October 2021
- .
- (PDF) from the original on 16 July 2016.
- ^ Michael Le Page (27 June 2019). "It turns out planes are even worse for the climate than we thought". New Scientist. Retrieved 13 October 2021.
- .
- .
- S2CID 128789946
- S2CID 4348401.
- ^ Perkins, Sid. (11 May 2002), "September's Science: Shutdown of airlines aided contrail studies", Science News, Science News Online, retrieved 13 October 2021
- ^ S2CID 4425866.
- .
- Science Daily, 18 June 2015, retrieved 13 October 2021
- S2CID 4425866. Archived from the original(PDF) on 3 May 2006.
- doi:10.3354/cr026001.
- doi:10.1029/2008GL036108. Archived from the original(PDF) on 22 May 2023. Retrieved 6 January 2024.
- ^ Irfan, Umair (7 July 2011). "World War II Bomber Contrails Show How Aviation Affects Climate". scientificamerican.com (ClimateWire). Retrieved 13 October 2021.
- ^ Parry, Wynne (7 July 2011). "WWII Bombing Raids Altered English Weather". livescience.com. Retrieved 13 October 2021.
- S2CID 129296874.
- PMID 34924638.
- .
- .
- ^ a b McKee, Maggie (9 November 2010). "Mystery 'missile' likely a jet contrail, says expert". New Scientist. Archived from the original on 10 November 2010. Retrieved 10 November 2010.
- ^ a b West, Mick (10 November 2010). "A Problem of Perspective – New Year's Eve Contrail". Archived from the original on 12 November 2010. Retrieved 10 November 2010.
- ^ "Pentagon Can't Explain "Missile" off California". CBS. 9 November 2010. Archived from the original on 10 November 2010. Retrieved 10 November 2010.
- ^ Pike, John E. (November 2010). "Mystery Missile Madness". GlobalSecurity.org. Retrieved 11 November 2010.
- ^ Bahneman, Liem (9 November 2010). "It was US Airways flight 808". Archived from the original on 13 November 2010. Retrieved 10 November 2010.
- Mercury News/AP. 10 November 2010. Archived from the originalon 12 January 2012. Retrieved 11 November 2010.
- ^ Distrail on Earth Science Picture of the Day Archived 16 October 2002 at the Wayback Machine
- ^ Corfidi, Stephen; Brandli, Hank (May 1986). "GOES views aircraft distrails" (PDF). National Weather Digest. 11: 37–39. Archived (PDF) from the original on 21 April 2017. Retrieved 13 October 2021.
External links
- Contrail Education (archived) | NASA
- Contrails.nl: Contrails and AviationSmog Archived 20 February 2011 at the Wayback Machine | Galleys of contrails and aviation smog
- Contral Science | Reference site for debunking weird stories about contrails
- Dunning, Brian (15 February 2007). "Skeptoid #27: Chemtrails: Real or Not?". Skeptoid.