Monday, January 21, 2013

Mank and Murk in Utah County

Looking north over the smog of Utah County.
Courtesy Jeff Massey.
The most remarkable (and depressing) PM2.5 readings so far during this "Mother of All Inversions" event come from Utah County.

Online data from the North Provo site operated by the Division of Air Quality show that 24-hour average PM2.5 concentrations reached 104.3 ug/m3 this morning.  That is almost 3 times the National Ambient Air Quality Standard.

Source: Utah Division of Air Quality
I thought I would try and take a look at how this compares to recent events.  To do this, I went to the Utah Division of Air Quality Air Monitoring Center Data Archive for PM2.5.  There you can find a Byzantinian array of data.  I ended up grabbing the highest maximum 24-hour PM2.5 observation from any Utah county station during each year in the Yearly Percentile Frequency Report.

Plotted below is a comparison with our current event (the data for 2012 was not available).  Assuming I'm using the data in the archive correctly (this is an important caveat to consider as the data tables on the DAQ web site contain limited information), current readings at the North Provo site are higher than any measured in Utah county since 2000.

We will have to see if this stands up to a more careful analysis, including quality control of the North Provo data, but this does appear to be an exceptional event by recent standards.

Addendum 11:25 AM: suggests that North Provo has the highest air quality index (hourly PM2.5) in the US, with Logan a close second.



  1. Update to yesterday's commentary on PM2.5 concentrations and the Hawthorne monitor. Clearly, there appears to be something wrong with the Hawthorne monitor as we are on a steady downward trend into what would be relatively clean air. As such, the last few days of data likely are not accurate and today we see the same thing.

    While the monitor is state of the art we really need something that works more reliably here in the Salt Lake Valley under our unique conditions.

    Having said all that, I could be wrong and the monitor is measuring some unusual things going on with our particulate, but I dont think so.

    1. I agree. The long-term downward trend and the brief drop to near-zero PM2.5 concentrations last night seem unrealistic.

  2. One odd thing about the PM2.5 readings is that SLCo's vary greatly from hour to hour, whereas UtahCo's hourly readings are very consistent by comparison. Other counties like Weber and Tooele seem to be somewhere in between.

    Could this be due to different types of measuring equipment (unlikely) or slight differences in placement of the equipement (microclimates, elevation, proximity to buildings, interstates, factories, etc.)?

  3. What is needed, and this is easier said than done for many reasons, but to have different monitors side by side at the Hawthorne site and see what we get.