The dust storm that blew into the Valley of the Sun on July 5, 2011, was a monster. It covered 100 square miles of surface, extended 8,000 feet into the sky, and approached Phoenix at a speed of 40 miles per hour.
"I've never seen anything so incredible as that," said Ken Waters, who is warning coordination meteorologist at the National Weather Service's Phoenix office. He sent out the dust storm warning that day.
"We actually tracked that dust cloud about 300 miles. It actually went into California," said Waters.
This summer, Waters co-authored a study of dust storms, which laid out what researchers know about how they form, why they form, and whether the Valley is seeing more of them than it had in the past.
That final question has proved to be the most difficult to answer.
"The jury is still a little bit out on this," said Waters.
Statistics show that over the past 30 years, the average number of dust storms that have reached Phoenix Sky Harbor Airport has declined slightly. But those averages don't take into account the fact that there is less open space near the airport, as the suburbs have expanded, which has reduced the amount of nearby dust, or the fact that we have seen some years with the number of dust storms much higher than the average.
One such year was 2011, the year the monster storm blew into Phoenix.
There is some evidence that the storms that have reached the airport are stronger today than they were in the past. And Waters has a theory about that.
"It's quite possible that socioeconomic factors may have had a play in this," said Waters.
What he means is that the Great Recession that began in 2008 may have sped up a phenomenon that was already taking place in the area where these dust storms are born. That is the desert between Phoenix and Tucson. It's an area that has historically been home to lots of farms. But farming is on the decline. Some farmers have sold to developers. Others have just stopped tending to the land and are waiting for values to rise or for an offer from a developer.
The result, according to ASU air pollution research professor Peter Hyde, is that there is now 300,000 acres of abandoned farmland in Pinal and Maricopa Counties. That's 469 square miles, about the same size of the City of Los Angeles.
"I had no idea," said Hyde, until he started tallying up the numbers.
Hyde believes the abandoned farmland is contributing to the massive dust storms the Valley has witnessed over the past 10 years, although he, too, says he has been unable to come to a conclusion as to whether we are seeing more storms than before.
"I've been looking at it, but so far I haven't gotten very far," said Hyde.
What he has identified is a gap in the regulations that govern dusty land in Arizona. While active farmers are required to abide by blowing dust standards, there are no such regulations that cover abandoned farmland.
"The reason I am concerned about abandoned agricultural land is it's the only one that doesn't have a regulator umbrella over it, as all the others do," said Hyde.
He has met with one state legislator about the need for regulations to reduce the amount of dust that is available to become airborne during our summer thunderstorm season.
The idea that these abandoned plots are adding to the severity of the Valley's dust storms is just a theory so far. But if it turns out to be true, the Valley will witness many more of the massive storms, as more farmers quit working the fields, and those fields turn to dust.
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