Rapid Worsening of Air Quality over Puget Sound Today

Air quality declined very rapidly today as temperatures rose back into the mid-80s.   Not only was the degradation obvious on air quality sensors, but visibility clearly worsened during the day.  To illustrate, here are two images from today (top) and yesterday (bottom) from the Seattle Panocam at 4:50 PM.  Much worse today.

Take a look at the small particulate measurements (PM2.5 concentrations) from some local reporting stations (graphic from Puget Sound Clean Air Agency).  Huge rise during the day today at Seattle, Tukwila, and Tacoma...with air quality today comparable to August 3/4.    Really nasty and unpleasant out, with a number of folks complaining to me about coughs and sore throats.

Why did the air quality get so bad today, something that several of us were forecasting two days ago?

 First, the low level winds over western WA switched from onshore (southwesterly and westerly) to northerly and northeasterly, thus bringing in the smoky air from the wildfires in BC.  The time/height cross section of winds/temperatures above Seattle illustrates this change.

Another major change was greater vertical mixing.  With less cool marine air near the surface, the inversion aloft, which acted as a barrier to the smoke aloft, was weaker and that allowed surface heating to mix the air in the vertical.   That is why the air quality declined during the day...vertical mixing was bringing down more and more smoky air.

Levels of PM2.5 particulates of 60-90 micrograms per cubic meter, what we saw this afternoon, are definitely unhealthy for vulnerable populations and ruin our typically great views of the water and mountains. Tomorrow should be more of the same.

Yesterdays smoke aloft really messed up the Blue Angels presentation, with the aircraft quickly disappearing into the muck as the rose vertically.  And when I flew into Sea Tac on Friday evening, the scene below was other worldy (see below).