Phoenix Area High Temps a Treat, but Air Quality Poor

John Faherty
Arizona Republic

The new year has begun with nearly perfect weather. Nearly.

A high-pressure system hovering over the Valley brought warm afternoons perfect for long walks, golf or winter gardening. High temperatures in 2012 have been running as much as 10 to 15 degrees above normal.

And the nights have been crisp and chilly, ideal for a blanket.

But there are consequences.

“When we get high pressure overhead, the air becomes more stagnant,” said Valerie Meyers of the National Weather Service.

This is called a subsidence inversion, which keeps air from rising and mixing with cleaner air.

“It holds in the particulates, and you can see the result,” Meyers said.

The result is fine-particulate pollution that exceeds the federal health standard. On New Year’s Day, Maricopa County air-monitoring data showed levels three times what is considered healthy.

The air has gotten better since, but incrementally. The Weather Service forecasts the high-pressure system will begin to fall apart over the weekend. That should bring the highs down by about 10 degrees, but it should also help clear the air.