Editing Dust devil (section)

== Formation ==
[[File:Dust devil krakow.jpg|left|thumb|A dust devil in [[Kraków]], [[Poland]]]]
Dust devils form when a pocket of hot air near the surface rises quickly through cooler air above it, forming an updraft. If conditions are just right, the updraft may begin to rotate. As the air rapidly rises, the column of hot air is stretched vertically, thereby moving mass closer to the axis of rotation, which causes intensification of the spinning effect by [[conservation of angular momentum]]. The [[Secondary flow#Tornadoes and dust devils|secondary flow]] in the dust devil causes other hot air to speed horizontally inward to the bottom of the newly forming vortex. As more hot air rushes in toward the developing vortex to replace the air that is rising, the spinning effect becomes further intensified and self-sustaining.<ref name="NWS">{{cite web |title=Dust Devil |url=https://www.weather.gov/fgz/DustDevil |website=weather.gov |publisher=National Weather Service |access-date=26 May 2021}}</ref> A dust devil, fully formed, is a funnel-like chimney through which hot air moves, both upwards and in a circle. As the hot air rises, it cools, loses its buoyancy and eventually ceases to rise.  As it rises, it displaces air which descends outside the core of the vortex. This cool air returning acts as a balance against the spinning hot-air outer wall and keeps the system stable.<ref>{{cite book |author = Ludlum, David M. |author-link=David M. Ludlum |year = 1997 |title = National Audubon Society Field Guide to North American Weather |publisher = Knopf |isbn = 978-0-679-40851-2 |url-access = registration |url = https://archive.org/details/audubonsocietyfi00ludl }}</ref>

The spinning effect, along with surface [[friction]], usually will produce a forward momentum. The dust devil may be sustained if it moves over nearby sources of hot surface air.<ref>{{cite web |last1=Thompson |first1=Andrea |title=How Do Dust Devils Form? |url=https://www.scientificamerican.com/article/how-do-dust-devils-form/ |website=Scientific American |access-date=26 May 2021}}</ref>

As available hot air near the surface is channelled up the dust devil, eventually surrounding cooler air will be sucked in. Once it occurs, the effect is dramatic, and the dust devil dissipates in seconds. Usually it occurs when the dust devil is moving slowly (depletion) or begins to enter a terrain where the surface temperatures are cooler.<ref name="death-valley">{{cite web |title=What is a Dust Devil? |url=http://www.death-valley.us/article559.html |website=Death-Valley.us Forums |access-date=17 May 2023 |archive-url=https://web.archive.org/web/20030603164203/http://www.death-valley.us:80/modules.php?name=News&file=article&sid=559 |archive-date=2003-06-03 |date=May 20, 2003 |url-status=dead}}{{cbignore}}</ref>

Certain conditions increase the likelihood of dust devil formation.
* '''Flat barren terrain, desert or tarmac:''' Flat conditions increase the likelihood of the hot-air "fuel" being a near constant. Dusty or sandy conditions will cause particles to become caught up in the vortex, making the dust devil easily visible, but are not necessary for the formation of the vortex.
* '''Clear skies or lightly cloudy conditions:''' The surface needs to absorb significant amounts of solar energy to heat the air near the surface and create ideal dust devil conditions.
* '''Light or no wind and cool atmospheric temperature:''' The underlying factor for sustainability of a dust devil is the extreme difference in temperature between the near-surface air and the atmosphere. Windy conditions will destabilize the spinning effect of a dust devil.