Editing Contrail (section)

==Distrails==
[[File:10sec old Distrail in Hong Kong.jpg|thumb|A distrail is the opposite of a contrail]]

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.<ref>{{cite web |title=Distrail on Earth Science Picture of the Day |url=http://epod.usra.edu/archive/epodviewer.php3?oid=110784 |website=epod.usra.edu |access-date=11 January 2008 |archive-date=16 October 2002 |archive-url=https://web.archive.org/web/20021016164705/http://epod.usra.edu/archive/epodviewer.php3?oid=110784 |url-status=dead }}</ref> An early satellite observation of distrails that most likely were elongated, aircraft-induced [[fallstreak holes]] appeared in Corfidi and Brandli (1986).<ref>{{cite journal |last=Corfidi|first=Stephen |author2=Brandli, Hank |title=GOES views aircraft distrails |journal=National Weather Digest |date=May 1986 |volume=11 |pages=37–39 |url=http://nwafiles.nwas.org/digest/papers/1986/Vol11-Issue2-May1986/Pg37-Corfidi.pdf |archive-url=https://web.archive.org/web/20170421061015/http://nwafiles.nwas.org/digest/papers/1986/Vol11-Issue2-May1986/Pg37-Corfidi.pdf |archive-date=2017-04-21 |url-status=live  |access-date=13 October 2021}}</ref>

Clouds form when invisible water vapor condenses into microscopic water droplets or into microscopic ice crystals. 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: