Wednesday, November 28, 2012

Intricacies of Inversions

Looking out over the northern Salt Lake Valley and southern Great
Salt Lake from the Avenues Foothills yesterday @ 430 PM MST
Although the past few days seem pretty boring weather wise, they are simply fascinating for a micrometeorologist.  The contrasts in surface temperatures in northern Utah have been astounding.  Let's take yesterday afternoon as an example.

At 2200 UTC (300 PM MST), it was a balmy 56ºF on the University of Utah campus and 58ºF just up the hill at the Utah Museum of Natural History.  However, at the Salt Lake City International Airport, which is about 500 feet lower, it was only 50–52ºF.

Source: MesoWest
This reflects the incredibly shallow nature of the inversion.  However, it gets even more interesting if you look out over the Tooele Valley where temperatures were only in the 40s.  During many inversions, especially those without snowcover, afternoon temperatures over the lake are often much colder than those over the surrounding land.  The Tooele Valley more "vulnerable" to this lake influence that the Salt Lake Valley, and is often much cooler under these conditions.

The situation this morning is also fascinating.  The morning sounding from the Salt Lake City airport shows that the inversion"\ is extremely shallow and actually consists of two distinct inversion layers, one that is based right at the surface (and is confined to the lowest part of the valley), and another that is just above it.  You can just make out a break between these two layers at 850 mb.

One can literally see the surface-based inversion this morning from the Avenues.  Look at the smog layer that is hugging the valley floor.

Looking west from the Avenues @ 845 am MST
When you have a shallow inversion like this, there can be strong contrasts in air quality in the Salt Lake Valley.  The situation in the lowest elevations can be markedly worse than on the benches.

1 comment:

  1. Has anyone studied inversions in the Sanpete Valley? Sunday morning it was 20F in Fairview when we drove thru, then it shot up to 32F on Skyline 20mins later..