A dust devil is a spinning vortex of air that starts at the ground due to strong differential heating of the surface by the sun. The vortex is triggered by a quickly rising thermal near the ground; the vorticity in the air makes the air inflow spiral to the low pressure under the thermal, concentrating into a vortex. The fast spinning air may kick up dust or grass, making the vortex visible, and sometimes even intensifying the vortex due to increased absorption of sunlight.
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