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My understanding is that a dust devil is created when heated air rises rapidly displacing the cooler air above up. My question is, how relatively hot does the patch of air on the ground have to get in order to create a dust devil, and how is the heat related to the height and size? And secondarily, do dust devils tend to occur more frequently within a certain range ambient temperature?

dust devil illustration

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    $\begingroup$ I have personally seen dust devils created at landfills over black plastic liner is being installed. The air temps are 70-80s'F but the temp on the liner is over 100'F. I suspect it is a relatively low temp difference profile can be create the motion. Water sprouts on Lake Erie are common late summer into early autumn when the cooler calm air flows over the lake but the lake temps are 10+ degrees warmer than the air. $\endgroup$ – Gary Kindel Jan 9 '18 at 20:51
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    $\begingroup$ It might be that nobody has studied dust devils to that extent simply because it is super hard to get the data. $\endgroup$ – Communisty Jan 10 '18 at 12:28
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    $\begingroup$ Ha! Move to Phoenix, AZ. We have plenty here. Occasionally one will get large enough to cause actual damage, up to and including launching a bouncy castle quite a distance. I lived in WA state before moving here 15 years ago. I seldom saw them in Western Washington, but they are a regular event in the PHX area. Last week I drove through one that was parked inconveniently in an intersection. Temps might have been 80F. They last a lot longer than dust devils I've seen elsewhere. Merely anecdotal info.... $\endgroup$ – Tim Nevins Mar 22 '18 at 21:14
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When a parcel of dry air with a given initial temperature rises, it cools at a specific rate - the dry adiabatic lapse rate. If the surrounding environment cools at a slower rate with height than the parcel, the parcel will eventually be colder than the environment and sink. On the other hand, if the environment cools faster than the parcel does, the parcel remains warmer than the environment and rises freely.

So for a parcel of dry air to continue to rise, the environmental lapse rate needs to be greater than the dry adiabatic lapse rate. Surface heating does a really efficient job of increasing low-level environmental lapse rates, which is why dust devils are more common when there's more sun.

I'm not a scientist, so I can't tell you an exact number, but the dry adiabatic lapse rate is 9.8 degrees Celsius per kilometer, or 3.3 degrees Fahrenheit per 1,000 ft. So if the environment cools at over 1 degree C per 100 meters, it will likely be conducive to dust devils.

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