Roadside Rest

Roadside Rest The Arizona Desert's Mysterious Devils Can Be the Source of Many Surprises

Last summer I was tooling along Bell Road, an east-west artery in far north Phoenix, when unfolded an astonishing event. As if in violation of laws of gravity and energy, a huge por-table billboard levitated 100 feet from the tarmac, somersaulted thrice, and loudly slammed down onto the cab of a pickup truck. Ouch! Presently the cause of all the commotion revealed itself as it pounced onto a dry fallow field. A great gout of fine dirt rushed skyward to give shape to a spinning column of wind. A dust devil.

Although they can spawn most any place in the world where the ground is flat, dry, and heated by the sun, Arizona seems to generate more than its fair share.

Not so small, some of them. These hot weather desert twist-ers have been measured a mile and a half high. Not uncom-monly they bulge out to a hundred-foot diameter. It is the published opinion of Professor T. Theodore Fujita, when he was a whirlwind expert at the University of Chicago, that a strong dust devil is more powerful than one-fourth of the world's tornadoes.

For more than a century, the Arizona press has documented remolinos unroofing stables, wrecking homes, felling churches. According to physicist Dr. Sherwood B. Idso, Arizona's resident expert, "It is reported that a dust devil once formed over a railroad embankment that was under construction and removed a cubic yard of sand per hour from it for four hours. Its erosive action could not be stopped until a bulldozer was finally driven into it!"

Neither legends nor tall tales, dust devils often register on police and fire departments' ledgers. One July long ago, I was covering the crime beat when on an otherwise becalmed day the fire station received what must have been a false alarm: building destroyed by wind.

Not even a zephyr was stirring. Mostly out of curiosity, the firemen and I responded to the call. Over on the west side, masons had just topped out a twostory cement block wall at a new industrial park. In the midst of this cloudless, breathless afternoon a tiny spiral had sprung off an asphalt parking lot, raced full-grown across a vacant lot, sucked up a column of brown dust, and slammed into that solid wall. Heavy blocks fell like oversize dominos.

Meteorologists say that dust devils proliferate where solar radiation heats a surface layer of air. The hot layer is held captive by relatively cooler air above. That is, until a little disturbance occurs, allowing a bubble of hot air to escape upward. The triggering mechanism might be so subtle as an unseen shear of temperature between torrid street and green lawn, so small as a child running across an overheated playground. Hot air abruptly ascends. Surrounding air joins in the stampede. The baby devil takes on a rotary motion. And in the principle of "conservation of momentum" that causes a spinning ice skater to accelerate as the limbs are drawn to the body, the maturing dust devil spins faster and faster.

In the 1970s, Daniel E. Fitzjarrald earned his doctorate in meteorology at UCLA by studying dust devils. By Jeep he followed a thousand of the twisters, some for as long as 10 miles. Fitzjarrald knew of one that lasted eight hours, but his personal champ spun only an hour. "Most of them last only five or 10 minutes, then poop out," he said. Paradoxically, dust devils usually form in calm air. Horizontal breezes tend to tear the devils apart.

But at their peak of power, devils do the darndest things. Family pets can be plucked aloft and deposited down the street. Devils can inhale a newspaper and hang it across the sky like a gang of flimsy kites. A woman I know swears a dust devil invaded her backyard, siphoned up an enormous water spout from the pool, and heaved it over a six-foot masonry fence. It took a patio table and two chairs with it.

Of course the mischief winds spawn some fiction. Some wags hold that the hot blasts originate in the Arizona Senate. Other desert dwellers declare that a dust devil is most likely to appear when (1) you have just suctioned up the last leaf from the bottom of your pool, (2) you have hung out a wash of filmy, fragile lingerie, and (3) you have set a picnic table with paper plates for a backyard barbecue. Scientists pooh-pooh these theories. Despite compelling evidence.

Anybody who has been caught in the gritty grasp of a serious dust devil has to question the logic of the greatest military victory of Muhammed II. The famous founder and sultan of the Ottoman Empire is said to have scooped up a handful of sand as he led his army to battle against Constantine XI's desperate defenders of Constantinople, the capital and last vestige of the Byzantine Empire.

As the sultan galloped near the Byzantine army, he tossed the sand into the air to trigger a monstrous twister. Muhammed II and his horse supposedly hid inside the churning sandstorm, which blinded his opponents. Yet how did the conquerer of Constantinople keep the grit out of his own eyes? Was his horse equipped with radar? Muhammed II would have been too busy clutching his tur-ban to swing his sword.

Pioneers in the West named the miniwhirlwinds "sand mills." To Mexicans they were diablitos, "little devils." The Tohono O'odham people considered them the works of a god, Hewultki. But leave it to the Navajos to coin a masterpiece of imagery. They call them "mothers-in-law."