Saturday, October 6, 2012

A Frontal Inversion

Inversion is a bad word in Utah, commonly associated with terrible air pollution.  We think of them as wintertime phenomenon, but they can occur anytime of year.

We have an inversion sitting over us today, created by the cold-air intrusions that have occurred the past couple of days.  Those intrusions have been shallow, and a frontal inversion sits at the top of the cold air.  Given that the cold air moved through Idaho, it is also filled with smoke.  That smoke has been mixed through the boundary layer (the layer where turbulence generated by the Earth's surface is strongest), but the inversion has prevented it from mixing above about 11,000 feet.  This was readily apparent at upper elevations in the Wasatch Mountains today.  

I've superimposed the morning sounding on the view to the west.  The nocturnal inversion at low levels in the sounding would have been burned off today by surface heating, but the frontal inversion (located just above 700 mb and near 11,000 ft) surely remains and is putting a lid on the atmosphere very near the summits of the higher peaks of the Wasatch.  

Fortunately, the inversion is fairly high, which means the smoke and pollution are distributed through a deep enough layer that the air quality won't be as bad as we see in the winter.  


  1. Agreed. I usually quietly enjoy the analyses provided here, but I just wanted to pipe up and say thank you.

  2. awesome idea overlaying the sounding on a photograph... that could be a really useful way to teach people how to "see" what the sounding is showing them