In between the winter rains and the summer monsoons of the Sonoran desert, is dust devil season. Smaller than haboobs, these dust tornadoes are quite remarkable. They are called dust devils because of the dust they pick up and spin in the air. With the lack of clouds and the higher temps, such as in the 90s Fahrenheit, the desert sand heats up. The air above the heated ground warms and rises. However, when this warm air hits the cooler air above, a small area of low pressure is produced. More warm air is drawn upwards into the now swiftly rotating column of air. As you can tell this blog is all about dust devils.
Dust is pulled up with the rising air leading to its descriptive name of a dust devil. The column will continue to rise until too much cooler air at the top is drawn in and collapses the vortex.
Most of the dust devils I see on my drive from Tucson to Marana are small, short-lived dust devils. The National Weather Service says that dust devils can be short in height, less than 100 feet tall, but some can reach 3000 feet. My parents and I encountered one of these bigger dust devils when we were traveling with a travel trailer. My father was driving and we were admiring a dust devil on the highway when we drove into it. The dust devil picked up our car and trailer and turned us around, putting us down and facing the opposite direction. I never underestimated a simple dust devil after that. After all, dust devils’ wind speeds can range from 45-80 mph! 80 mph would put it at the same intensity as a category 1 hurricane.
Nowadays, I encounter them on the highway or riding my horse in the arena. Horses don’t like dust devils. I either face the horse away from the dust devil if he hasn’t seen it or have them watch it if they had observed it heading our way. I don’t want any swirling dust surprises while on top of a thousand-pound animal with a mind of his own when it comes to reactions!
Usually, it’s mostly dust and dirt that is picked up, but larger debris may be caught up in the wind (like cars and trailers).
One reason dust devils are so prevalent in the area north of Tucson is the flat desert terrain. This makes it easier for the vortexes to form over the heated land. Also, since most days are sunny with few clouds, there’s sufficient sunshine to heat the ground. The desert environment with its low humidity allows the warm air to rise quickly. Humidity reduces the upward airflow.
What role do dust devils play in the desert ecosystem? The swirling winds would certainly disperse seeds over a wider area. Soil particles are also dispersed, adding to the creation of the desert soil, known as caliche. However, the spores of the fungus that causes Valley Fever, coccidioidomycosis, would also be flung farther than by wind alone.
I’ve been trying to get a good photo of a dust devil, but haven’t managed to catch one when I could take its picture. I’m usually driving or riding.
However, I’ll keep trying. Maybe I’ll be able to show you photos of the different kinds of dust events we have here: haboobs, tornadoes, and such, in a future blog. If you’re in the Sonoran Desert area, around midday, keep an eye out for the fascinating weather phenomena known as dust devils! In the meantime, check out some of my fun STEM-based workbooks all about the Sonoran Desert.
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