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Stagnant air mass increasing metro haze

Posted at 8:25 AM on September 15, 2009 by Paul Huttner (4 Comments)

GraphData.jpg
MPCA air qulity data shows particulate matter has increased the past two weeks.

You can literally see it in the air.

Those lazy hazy days of summer came in September this year.

Haze levels and particulate matter have increased in the Twin Cities the past two weeks. A persistent ridge of high pressure has created nearly stagnant air conditions in the metro. Light winds and calm air have been common the past few days, and that has allowed pollution levels to build in the area.

According to MPCA data, the level of particulates has been on the rise since September 2nd. The forecast is for levels to rise slightly the next few days.

In the Twin Cities, the highest wind the past three days has been a mere 7mph. You can see from the observations at Twin Cities Airport, the air has been calm for many hours. This means there is little horizontal movement of air, and no fresh air masses sweeping in off the Canadian Prairies. As a result fine particulate matter less than 2.5 microns in size from auto exhaust and wood smoke is just hanging around.

Everything's a trade off in life and sometimes in weather too. Our mild air mass will linger this week, and so will pollutants. If you're looking for cleaner air it will come next week with a Canadian cool front. The trade off is, it's going to start feeling like fall with much cooler temperatures.

Enjoy our last spell of summer in September through the weekend!

PH

Comments (4)

Is this anything to be concerned about if exercising outdoors early in the morning?

Posted by Luke Taylor | September 15, 2009 11:03 AM

Hi Luke:

Accoding to MPCA the AQI needs to reach 101 before it is considered "unhealthy for sensitive groups." Hopefully we will stay below that threshold.

Enjoy the jog!

PH

Posted by Paul Huttner | September 15, 2009 2:44 PM

2.5 millimeters? Don't you mean 0.25 millimeters, or 2.5 micrometers, or something?

2.5mm would be visible chunks in the air the size of sesame seeds. I think I would have noticed.

Posted by Peter | September 15, 2009 10:37 PM

Hi Peter:

You are aboslutely right. It is 2.5 "microns." I am confusing raindrop sizes somewhere im my weather brain.

I do like sesame seeds though! Reminds me of the book, "Cloudy with a chance of meatballs."

PH

Posted by Paul Huttner | September 16, 2009 7:39 AM

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