"I'm quite concerned about the long-range forecast," Steenburgh wrote in the blog, Wasatch Weather Weenies, "and the potential for unhealthy particulate matter levels in the Salt Lake Valley for several reasons."
Three factors are at work:
• Northern Utah's valley bowls, created by surrounding mountains.
• The high-pressure system that, along with temperature, acts like cellophane covering the bowls.
• Pollution that builds in the puddles of cold air at the bottom of those bowls.
Nanette Hosenfeld, a meteorologist with the National Weather Service's Salt Lake City office, noted that a low-pressure system brought snow and cleared the air over the weekend.
"Now we have high pressure," she said, "and it's basically like that cellophane [is]pressing the lid down."
In addition, she notes, the cold air, which is heavier than warmer air, is pooling at the bottom of the valleys and cooking the soup of pollutants, which are being emitted by everyday life, from heating to driving to grilling food.
As higher layers of air warm, the pollution stew simmers and creates even more pollution all of it kept in place under the layer of warm air stretched over the basin.
What makes this inversion so worrisome is the steep difference in temperature between the upper layers of air and the cold pools in the valley.
The bigger the differential, the tighter the sealing "lid" over the valleys and the less likely it is for clean air currents to carry away the pollution. And in the coming week, forecasters see a 40-degree difference between the upper layers of air and the air temperature close to the ground.
Plus, another factor for the week ahead is that the thick layer of snow on the ground will seal in the pollutants more tightly.
"It's the inversion that keeps the [polluted] air in place," said Steenburgh. "When we have an inversion, the air has no place to go."
In his blog entry, Steenburgh noted: "What happens with pollution will depend on emissions and chemistry. As Vince Lombardi said, the best defense is a good offense."
That's what the Utah Division of Air Quality seemed to have in mind when it raised the air-quality action rating to "red" on Tuesday in Utah, Salt Lake, Davis, Weber and Cache counties. That means anyone using wood-burning stoves and fireplaces is subject to fines.
By trying to limit combustion emissions like this, air-quality officials are hoping to control the one smog factor that is in the hands of Utahns: their pollution. There are many suggestions for reducing emissions at the state's Choose Clean Air webpage, www.cleanair.utah.gov/.
And as bad as the air could potentially get here, Utahns may or may not find some small consolation that our particulate pollution doesn't begin to approach that of Beijing.
Under the U.S. Environmental Protection Agency's standard, sustained concentrations of 35 micrograms of PM 2.5 per cubic meter of air are considered unhealthy.
On Saturday, the U.S. Embassy in Beijing reported PM 2.5 levels of 886. Utah's highest levels last week were less than a tenth of those in China.
Twitter: judyfutah No one source provides all of the relevant information on what's happening with Utah's air quality from day to day. Here's some advice from Utahns who follow the issue closely.
Where can I find out about restrictions on burning wood? • It is illegal to use most fireplaces and wood-burning stoves on red days. To find the latest advisory, see the Utah Division of Air Quality's forecast webpage. You can also sign up on that page for email alerts that are sent twice daily during the winter and summer pollution seasons. > www.airquality.utah.gov/aqp/slc.html
What's the best way to learn pollution levels in my area? • Check the DAQ's "current conditions" link on the webpage, which gives current PM 2.5 pollution concentrations county by county. PM 2.5 causes harm when the tiny particles penetrate the lungs. For some, even low levels have an impact. Others have a higher tolerance for pollution before they feel it.
Brock LeBaron, DAQ deputy director, said he checks the trends, especially in timing when he bikes or runs outdoors. "I want to know what the pattern is and how it relates to recent [pollution] values." > www.airquality.utah.gov/aqp/slc-currentconditions.html
When are pollution levels considered harmful? • The U.S. Environmental Protection Agency has set a level of 35 micrograms of PM 2.5 pollution per cubic meter of air as its health-based standard. If the average daily concentration goes above that, the state is in violation of the federal standard. You can also see the patterns of pollution in the "trends charts," which you can link to on DAQ's main webpage. > http://1.usa.gov/uQB24i
Breathe Utah's Karen Hevel-Mingo noted that her husband, Richard Mingo, checks levels online each day before commuting on his bicycle. If the daily trend reaches a certain level, he'll limit his ride, sometimes jumping on public transportation partway to spare his lungs.
Where can I find out how local air quality stacks up against the rest of the nation's? • EPA's AIRNow uses a different formula than the state for rating pollution levels. It focuses on health impacts, rather than the what-you-should-do approach of the state's red-yellow-green air-action advisories. The webpage also offers a smartphone application for iPhone and Android devices. > www.airnow.gov/