Powerful Dust Storm Hits Phoenix, Arizona, USA

07/06/2011 19:25

The Star:  In the dirty ’30s, Canadians knew them as “black blizzards.’’ Now dust storms, like the massive one that swept over Phoenix and the Arizona desert Tuesday with a wall of dust reaching as high as 3,000 metres, have a new moniker — haboob.

It comes from the Arabic word habb, or wind, Environment Canada senior climatologist Dave Phillips said. While the word isn’t used often in Canada, it’s a common term in the Middle East and is becoming widely used in the desert states in the U.S.

Tuesday’s haboob in the Phoenix area was one of the worst in years, residents said, and videos of it went viral on the web. Strong winds, gusting up to 95 km/h, moved an 80-km-wide dust cloud across Phoenix and surrounding cities of Avondale, Tempe and Scottsdale, downing trees, delaying air flights and leaving thousands without power.

Its intensity may be unusual but this week’s Phoenix haboob is typical of the “monsoon season’’ that the desert state is now in, says Phillips. In Arizona, it typically starts in mid-June and lasts through September.

During the monsoon period, “you get these storms off the Pacific,’’ Phillips said. A high pressure area off the coast will encourage air to flow from the ocean onto land, eventually bringing thunderstorm and rains.

There’s a certain cooling when the rain falls but in the desert areas like Arizona, the air is so dry that the rain doesn’t even reach the ground, Phillips said.

“The air is so dry, so hot, it’s dry as a bone. The rain doesn’t stand a chance,’’ he said. “It evaporates. That cools the air and it will encourage the winds to get stronger.’’

That’s when they can become strong enough to pick up loose sand and dust and “the gusts move it back up into the atmosphere to create a wall of sediment,’’ the climatologist said.

Deserts are expanding on the planet “due to human activity. People are removing vegetation and exposing more land to these strong winds,’’ he said.

One of the areas where this is happening is in China, around the Gobi desert, which is expanding, said Phillips, due to poor land use and cutting back vegetation. As a result there are more haboobs in the area.

“The dust gets caught up in the upper atmosphere, in jet stream, and gets carried thousand of kilometres,’’ he said, ending up in Korea and Japan and there have even been traces detected in Canada.

It’s similar to what happened in Canada and the U.S. during the 1930s, when a Dust Bowl was created on the prairies and in the Midwest. A drought and poor farming methods turned the soil into dry dust which got carried away in wind storms.

Today, prairie farmers use better methods of farming and “they’re able to do a lot better with the same amount of water, than they could in the ’30s.’’

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