Worst Air Quality of the Season So Far Is Coming

Over the past two days, Mother Nature has been scouring away the inversion from the top down, but unfortunately a shallow layer of cold, gunky air remains over the Salt Lake Valley this morning.

The shallow layer of cold air can be seen very well in this morning's sounding.  The surface temperature was 35ºF (1.6ºC), whereas it was 4.8ºC at 838 mb, about 1500 ft above the valley floor.

Source: SPC

As a result of this top-down scouring out of the inversion, the air quality on the benches has improved dramatically.  The graph below shows the PM2.5 concentrations near the University of Utah dorms and the mouth of Red Butte Canyon over the past week.  Note the high values on January 2nd and 3rd, but also some big drops overnight on the third and then again last night as the inversion shallowed and cleaner air moved in.  Currently PM2.5 levels are running at about 7 ug/m3.

Source: MesoWest.

In contrast, a shallow layer of gunky air remains on the valley floor, as illustrated by the time series below from Hawthorne Elementary.  There has been some decline in PM2.5 concentrations, but they are still sitting near 20 ug/m3.

Source: DAQ

Web cams show the shallow layer of gunky air quite well.  The image below is taken toward the northwest from Olympus Cove.

Source: MSI

Unfortunately, I don't think that shallow layer will mix out today and that we're going to be stuck with at least some of this pollution as an upper-level ridge builds in an strengthens the next couple of days.  We are headed into what will probably be the worst air quality of the inversion season so far.