We begin with a time series of PM2.5 concentrations at the Hawthorne Elementary site maintained by the Division of Air Quality. Hourly PM2.5 concentrations (brown values) show large swings over the past three days with peaks in the late afternoon or evening and valleys overnight. Yesterday evening we hit the highest values of this episode with a peak of 51.6 ug/m3.
|Source: Utah Division of Air Quality|
The large diurnal swings in PM2.5 are very evident in the data being collected along the Trax lines the past couple of days. Observations collected in the 3-hour period ending at 8 PM MST last night showed very high values of 45–55 ug/m3 along the entire green line from West Valley city to the Salt Lake City Airport, consistent with that measured at Hawthorne above.
In contrast, we find lower concentrations this morning (but still in the moderate or unhealthy for sensitive groups air quality categories depending on location), as illustrated by observations collected along the red line from Daybreak to the University of Utah. Concentrations are lowest in the Daybreak area along the West Bench, and highest along the valley floor. Concentrations are also a bit higher at the University of Utah than at Daybreak.
It will be interesting to see how things evolve today, but I would expect to see another major rise in PM2.5 concentrations this afternoon. This is true even on the benches. Note how our sensor at the University of Utah climbed to a peak of 45 ug/m3 yesterday afternoon. Although not as high as observed at Hawthorne on the valley floor, these are still high values considered unhealthy for sensitive groups.
The only way to escape the poor air quality is to head to the mountains where the air is crystal clear and the visibility essentially unlimited.