Deeper and Dirtier

The weak upper-level trough and cold front pushing through northern Utah today has stirred the pollution a bit, but has thusfar provided little relief.  I went for a hike this afternoon in the avenues foothills and the pollution is deeper today than it was yesterday.  The photos below show the deepening and thickening of the smog over the 3 days since Christmas.

Here are a couple of additional views, the 2nd photo taken from my place in the Avenues at 4:30 PM for comparison with those in previous posts, although skies were overcast at that time making it look even bleaker.

24-hour average PM2.5 peaked this afternoon at 42.8 ug/m3, the highest of the event thusfar.  Hourly PM2.5 did drop in the past couple of hours, in contrast to the previous couple of days when it became elevated around noon and stayed that way all afternoon and evening.  Perhaps we are seeing a bit of mixing related to the upper-level trough and cold frontal passage, or the cloud cover that moved in this afternoon has lack of sun is affecting the photochemistry (not my area, so maybe others can comment).  It would sure be nice if it were the former.

Source: Utah Division of Air Quality