September 20 th 2014 Case Study

Observed increases seen in Ozone (MTMET; Sept 20 th ) and PM 2.5 (Hawthorne; Sept 19-21) measurements, wildfire related?

Significant wildfire activity being observed across central and northern California (Kings fire #10 by Lake Tahoe the largest of these)

MODIS visible image of the King wildfire Significant canopy vegetation in this region, probably lots of emissions

California wildfires could have impacts on SLC air quality though previous work has shown that these wildfires generally have smaller impacts (on average)

NOAA Hazard Mapping System Fire and Smoke Product suggests that some smoke could be making it to SLC, though this isn’t necessarily the most robust case I’ve seen from this product…

Source:

Source:

What does STILT think? STILT is a Backward Lagrangian Dispersion model which was driven by 12-km NAM wind fields for this particular case The following analysis uses the STILT footprint which measures the upstream “surface” influences on air that eventually arrives at SLC (which is our receptor)

*Note that UDAQ time in LST so apply 6-hour offset! King Wildfire

*Note that UDAQ time in LST so apply 6-hour offset!

King Wildfire *Note that UDAQ time in LST so apply 6-hour offset!

King Wildfire *Note that UDAQ time in LST so apply 6-hour offset!

King Wildfire *Note that UDAQ time in LST so apply 6-hour offset!

King Wildfire *Note that UDAQ time in LST so apply 6-hour offset!

King Wildfire *Note that UDAQ time in LST so apply 6-hour offset!

Conclusions California wildfires likely had an impact for the September 20 th episode Footprints over California weaker though if the magnitude of the emissions are significant enough (i.e large enough fire), these fire can have an impact on the air arriving at SLC Something to keep in mind is that the King fire likely has a sufficiently large heat flux which may be injecting emissions into the troposphere (a more common trait of large canopy fires) Plume rise issue, which is currently not parameterized in STILT footprints… yet! PM 2.5 increase can also be potentially explained by fires, though the initial large increase likely came from a different source as the footprint was orientated in a southerly direction during this time Speciated PM 2.5 data could confirm the source. The southerly wind direction makes me think this could be dust? A more thorough analysis is needed to confirm this.