|Looking north toward downtown from Cottonwood Heights|
|Panorama from the Avenues|
PM2.5 concentrations provided by the Division of Air Quality also show that the air is "cleaner" in a relative sense. PM2.5 concentrations peaked at nearly 100 ug/m3 yesterday, but lowered overnight. Nevertheless, PM2.5 concentrations lingered near the NAAQS standard through this morning before dropping below 20 ug/m3 at mid afternoon. Given the spatial variability in haze and smog this afternoon, there may be locations around the valley with higher concentrations.
Because of the weak flow, the removal of polluted air from the Salt Lake Valley has been slow and one can see evidence of urban pollution in the Wasatch Mountains today. For example, there was quite a bit of haze at times in White Pine Canyon today.
Further evidence of the transport of urban pollution into the Wasatch Mountains is provided by CO2 measurements from the top of the Snowbird tram. CO2 concentrations climbed from near unpolluted background values of ~392 ppm late in the day yesterday (Jan 08) to ~396 ppmm today, with a spike to 404 ppm. I suspect that the spike reflects the movement of air with considerable urban influence over Snowbird.
Today provides a nice example of the gradual removal of urban pollution by vertical and horizontal transport and mixing. It provides a nice opportunity to observe processes that usually operate much more quickly.