Where Today's Dust Is Really Coming From (Not Sevier Lake)

The Wasatch Front has long had episodes of poor air quality related to elevated PM2.5 concentrations during our dreaded wintertime inversions.  We have also seen episodes of elevated and sometimes unhealthy PM2.5 concentrations due to blowing dust.  There are multiple dust sources in southern and western Utah, but this winter, the Cedar Valley west of Utah Lake has been especially productive.

One of our post-docs, Derik Malia, first brought this source region to my attention in December.  In my blog post on December 21, we discuss two major dust plume events that clearly originated from the Cedar Valley on 3 December and 19-20 December.  Below are MODIS imagers of those two events clearly showing the plume extending from the Cedar Valley to the Salt Lake Valley.

Today?  Same story.  The latest MODIS shows the Cedar Valley is the primary source for the dust impacting the Salt Lake valley.  Look at the clear plume that begins just to the west of Utah Lake.

Sadly, media reports, such as the one below in the Deseret News (available in full here), are stating that the dust is coming from the Sevier Lake Bed.

This is also being suggested in the tweet below from the Utah DEQ.

It's windy out there. Along with the wind there is an elevation in PM10 pollution. Size is the big difference from the PM2.5 we see during inversions. This is mostly dust being blown around--some as far away as dry lake beds in Millard County.https://t.co/P9oj79jV7U

— Utah DEQ (@UtahDEQ) April 16, 2018

The Sevier Lake Bed can be an important source for dust, but in the MODIS image for this afternoon, that dust is going northward into the West Desert (look closely).  Our dust today, and in the December events, is coming primarily from the Cedar Valley.

These plumes are repeatedly impacting over 1 million people in the Salt Lake County and portions of Utah County.   Dust from these plumes, once deposited on the Wasatch snowpack, result in an accelerated snowmelt due to greater absorption of solar radiation.  

Reducing emissions from the Cedar Valley won't eliminate wind-blown dust events, but it would certainly reduce the frequency, duration, and severity of these episodes in the Salt Lake Valley.