Smoke from prescribed fire on October 17, 2017

I have been testing AOD (aerosol optical depth, a measure of light extinction due to aerosols in the atmosphere) devices this week. As such, I've been comparing results with nearby AERONET sites (https://aeronet.gsfc.nasa.gov/). I was looking at the NEON_CVALLA site and noticed this weird spike in AOD in the afternoon yesterday (October 17^th). I checked the other sites and saw spikes at the NEON_RMNP site, Table Mountain site, and high values at the Digital Globe calibration site. These are all Level 1 products, so they may not pass quality checks, but I still thought it was strange and warranted further investigation.

Level 1 AOD from NEON_CVALLA site on 17th October 2017. Image from: https://aeronet.gsfc.nasa.gov/cgi-bin/type_one_station_opera_v2_new?site=NEON_CVALLA 

I checked HMS, and I noticed some fires near Fort Collins, which I assumed were probably prescribed fires since they aren't there today. Zooming in, I more clearly saw that there was indeed some smoke produced from the fires.

HMS Smoke and Fire product for October 17^th, 2017 over the whole western US (left) and zoomed in over northern Colorado (right). Data from: satepsanone.nesdis.noaa.gov.

I double-checked this against MODIS. There was no smoke noted from the Terra instrument (which has a morning overpass), but there was smoke visible from the Aqua instrument (which has an afternoon overpass).

MODIS True Color Images from Terra (left) and Aqua (right) for October 17^th, 2017.

I checked if there was any impact on our surface air quality, and there was a slight increase in PM_2.5. Coarse PM (2.5-10) also increased. The timing seems earlier than what was noted by the satellites, but the satellites may have not picked it up in the morning and the smoke may have not made it to the AERONET sites until later in the day. There is also a diurnal cycle to the PM time series where concentrations are higher in the morning and night, and low during the day. This could be from the boundary layer trapping concentrations near the surface. Then, as the boundary layer grew throughout the day, concentrations decreased. It's hard to untangle all of this and directly attribute both the PM changes in Fort Collins and the AOD spikes at AERONET sites further downwind to this smoke, but it seems to be at least a plausible source.

PM_2.5 and Coarse PM concentrations measured in Fort Collins, CO for October 16-18^th, 2017.

Another double-check that this was indeed a prescribed fire sent me to InciWeb (where all fire incidents are recorded), where I found that the smoke was likely from the Pingree Hill Prescribed Burn (https://inciweb.nwcg.gov/incident/4727/) as its location generally matched the location from the satellite data. They burned 95 acres yesterday.

More transported smoke from the west October 12-13, 2017

If you've been following the news, you'll have likely heard about the terrible wildfires raging in California. Many people have died, homes and businesses have been destroyed, and some of the worst air quality on record has been measured. The strong dry winds are not helping the situation, and many people have been evacuated as the fires continue to spread. This has been a long fire season. I was getting ready to write a summary of the season (which I will post soon), but we are getting more smoke now in Fort Collins.

I noticed the smoke as I was leaving work last night (October 12^th*), and I snapped this picture (getting use to my solar field pictures yet?). It looked hazy again today (October 13^th).

Looking north northwest from the CSU Atmospheric Science building at 5:08 PM MT on 12 October 2017.

CDPHE had this Colorado Smoke Outlook today (October 13^th):

COLORADO SMOKE OUTLOOK: Friday, October 13, 2017, 8:05 AM MDT Wildfire smoke is being transported into Colorado from fires burning in the western United States. Impacts from this smoke are most likely along the Northern Colorado Front range and for locations east of the Continental Divide, however hazy and smoky skies may be noticed throughout the state. No significant impacts on public health are expected.

Where is this smoke from?
Trying to determine the source of the smoke, I turned to the satellite images. The source hasn't been as clear to me because the plumes are not as distinct. The MODIS-Terra images did look like there was some smoke over Wyoming and Utah earlier in the day yesterday.

MODIS-Terra True Color Image from October 12^th, 2017. Retrieved from https://worldview.earthdata.nasa.gov/. The line is from the two different overpasses being put together. 

The HMS smoke product seems to agree, showing plumes stretching over Utah, Wyoming, and NW Colorado both on October 12^th and October 13^th that could have hit us in Fort Collins as well. There was also a prescribed fire near Denver, a wildfire in Utah, and some prescribed fires in SE Idaho. Some of the smoke forecast models (Bluesky and HRRR) seemed to suggest that some of the smoke in Colorado could be from those sources as well. However, these do not show up in the satellite images, so I would wager a guess that this smoke is mostly from fires in California.

HMS smoke and fire product for 12 October 2017. Data from satepsanone.nesdis.noaa.gov.

What was the impact on our surface air quality?

You can notice the higher concentrations in the measured PM_2.5 in Fort Collins. The increase started right around the time that I was leaving work on Thursday, October 12^th.

PM_2.5 measured in Fort Collins, CO for October 10-13, 2017. Data from https://www.colorado.gov/airquality/.

*Originally posted October 13^th, updated October 17^th, 2017.