**** Info via Environment Canada
Spring is dust devil season via Environment Canada
Have you ever seen a dust devil?
Also called a “willy willy” in Australia, these dusty whirlwinds are a common occurrence in the world’s deserts, and even on the planet Mars.
When certain ingredients come together, dust devils can occur almost anywhere – and it turns out that these conditions occur most frequently in spring.
How do they form?
A dust devil is a dusty, rotating column of air in contact with the surface of the Earth. In many cases, they can be quite impressive to watch.
Like a miniature tornado, the vortex that makes up the dust devil requires two main ingredients – a source of swirling air at the ground, and something to stretch that swirling air upwards so that it increases its spin.
Think of a figure skater. As they enter a spin, they turn more slowly when their arms or legs are outstretched. As they bring their arms and legs in, they spin faster as their axis of rotation decreases.
A common way to get this “stretching” force is from the sun, which causes uneven heating of the ground. Some surfaces, such as roads or baseball diamonds, heat up more readily than their surroundings (like grass fields) on sunny days, especially when dry. This commonly occurs in spring, when the sun’s energy increases rapidly, causing warmer air columns to rise rapidly while the air above the ground remains relatively cool.
As air spirals into the column of rising air, it can be vertically stretched, intensifying into a dust devil!
While usually small, harmless and short-lived, some can grow quite large and intense. In fact, property damage, injury, and even death have occurred with the largest dust devils, so it is best to avoid getting too close.
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