Thursday, July 27, 2017

Smoke for July 23-24, 2017

If you were out and about in Fort Collins on Saturday (July 22nd), you might have noticed a large smoke plume. I took this picture from the North College King Soopers parking lot.
Taken looking southeast from North College King Soopers parking lot at 12:33 PM on Saturday, July 23, 2017.

A few minutes later I took this picture looking south from where 287/14 and 287B/54G split. 
Taken looking south southeast from 54G at 12:42 PM on Saturday, July 23, 2017.

This was smoke from the Spring Glade grass fire near Coyote Ridge Natural Area. The fire started at approximately 11 AM (according to the Coloradoan, it may have been caused when a mower hit a rock and caused a spark). The heat and wind unfortunately made the situation worse, and the fire spread pretty rapidly.

The CDPHE put out the following advisory at 5:30 PM that evening: 
Air Quality Health Advisory for Wildfire Smoke
Issued for Larimer County 4 miles southwest of Fort Collins
Issued at 5:30 PM MDT, Sunday, July 22, 2017
Issued by the Colorado Department of Public Health and Environment
Affected Area:  Locations in east central Larimer County near Horsetooth Reservoir and the Coyote Ridge and Cathy Fromme Prarie Open Space areas including, but not limited to, the Stout and Rim Rock areas and other portions of southwestern Fort Collins, and portions of northwestern Loveland.
Advisory in Effect: 5:30 PM MDT, Saturday, July 22, 2017 to 9:00 AM MDT, Sunday, July 23, 2017.
Public Health Recommendations: If smoke is thick or becomes thick in your neighborhood you may want to remain indoors.  This is especially true for those with heart disease, respiratory illnesses, the very young, and the elderly.  Consider limiting outdoor activity when moderate to heavy smoke is present.  Consider relocating temporarily if smoke is present indoors and is making you ill.  If visibility is less than 5 miles in smoke in your neighborhood, smoke has reached levels that are unhealthy.
Outlook:  Areas of moderate to heavy smoke will persist Saturday evening near Horsetooth Reservoir and the ridges and foothills adjacent to the fire. Light and variable winds are expected to be primarily out of the east or southeast late in the day on Saturday, however overnight, light drainage winds will allow smoke to reach lower terrain, below the fire. Depending on fire activity, moderate to perhaps heavy smoke is possible for neighborhoods in the immediate vicinity of this fire, while lesser concentrations and the smell of smoke will likely affect larger areas of south and southwestern Fort Collins and north and northwestern Loveland.

So, how did this affect our air quality in Fort Collins? 
Time Series of PM2.5 concentrations in Fort Collins (black) and Greeley (red) for 20 July - 25 July, 2017.
We did see that PM2.5 concentrations built up over night (from the 22nd into the 23rd) both in Fort Collins and in Greeley. The peak concentration was 19 ug/m3 at the Fort Collins monitor at 11 PM on Saturday night. Concentrations stayed higher on Sunday, July 23rd, but this could have also been from long range transport of smoke. Looking at the HMS for Sunday, there was smoke over northern Colorado from the fires in Montana and Idaho. The fires there are still burning, which is unfortunate for me as I'm travelling to Idaho and Montana this weekend.

HMS Smoke Product Plumes ( for July 23, 2017 at 1845 GMT (12:45 PM MT, left) and 2130 GMT (3:30 PM MT).

Friday, July 7, 2017

July 4-7, 2017

Leaving work Wednesday night at around 7 PM MST, I noticed the foothills looked a little hazy and the sun was a little more orange.
Looking west from the Department of Atmospheric Science parking lot at 6:56 PM MST on July 5, 2017.

I scooted home and took this next picture about 10 minutes later. You can see the sun is even more red-orange!
Looking west from Galway Drive in Laporte at 7:07 PM MST on July 5, 2017.
 We are used to lots of pretty pink sunsets here in colorful Colorado, so what's causing me to stop and take these pictures? First a little background on why we get  colorful sunsets. At sunset, the sun is lower in the sky, causing its rays to travel through more of the atmosphere and experience more scattering of blue light. This leaves a higher proportion of red light. However, these orange-red sunsets are a bit different. These are indicative of more small particles higher up in the atmosphere that are just the right size to scatter even more of the blue light, leaving the sky a beautiful red-orange.

What is the source of these small particles? Unfortunately for our health, they are smoke. Now, I am sure we have all been exposed to quite a bit of smoke the last few days with all the fireworks (especially if you live in Laporte like me!), but this smoke is likely from a wildfire. While the Peak 2 Fire ( near Breckenridge was all the talk Wednesday, my guess would be that this smoke was from either the Keystone Fire ( west of Albany, Wyoming or the Mill Creek Fire ( northwest of Hayden, Colorado.

The Hazard Mapping System (HMS) smoke product showed several different smoke plumes in our vicinity this week. For the last two days (July 6-7th), smoke pretty much blanketed the state.

HMS Smoke Plumes over northern Colorado for July 3-7, 2017.

I noticed this smoke on the morning of July 7th because I had hoped the air would be cleaned out after the rain the previous day. No such luck. While the sky was pretty blue, I could  see some smoke over the foothills as shown in the following pictures.
Looking northwest from the CSU Department of Atmospheric Science Campus at 10:58 AM on July 7, 2017.
We can look at the surface measurements of PM2.5 in the following time series and see that concentrations were about double the "normal" concentrations in Fort Collins on the evening of Wednesday, July 5th and into the morning of Thursday, July 6th. Concentrations did not reach the "Unhealthy" level, as most of the smoke was probably lofted above the surface. With all the different fires, it seems that we have had smoke every day this week.

Time series of hourly PM2.5 (top) and coarse PM (bottom) measured in Fort Collins for July 4th through the morning of
July 7th, 2017. 
There are two other interesting PM increases due to different sources on the time series plot. The 4th of July fireworks led to a really large increase on Tuesday night, and dust lofting before a storm on Thursday shows up in the coarse PM. A good reminder that there are lots of different sources of PM!

Thursday, July 6, 2017

Fort Collins Air Quality April 12-14, 2017

The warm weather probably brought a lot of people outside these last few days, but you may have also noticed that the foothills looked a bit hazy. Looking at the hourly time series of PM2.5 concentrations, we do see higher concentrations compared to previous days.

Time series of PM2.5 concentrations measured in Fort Collins, CO for 10 April - 15 April, 2017. Data courtesy of

So, what is causing these higher concentrations? Our guess would be smoke from prescribed fires. The CDPHE did not put out a specific warning for Northern Colorado, but there is the standard "Light to moderate smoke is possible near prescribed fires and small wildfires around the state."

The Hazard Mapping System also showed smoke plumes over northern Colorado/Wyoming on April 12-14. The plots show the plumes being transported different directions. While none of these show the plume directly over Fort Collins, the wind could have switched directions and blown the plume towards the southeast in between these times.

HMS Smoke Plumes and Fire Locations  in northern CO/southern WY for 12 April - 14 April, 2017. Data courtesy of

Checking inciweb (, there were a few prescribed fires around the state. Our guess would be on the Red Feathers Lake Prescribed Burn (

We also noticed however, that the coarse PM is high. This is often indicative of dust, which could have also been transported with the strong winds.
Time series of  coarse PM concentrations measured in Fort Collins, CO for 10 April - 15 April, 2017. Data courtesy of

What is a Prescribed Burn?
A prescribed burn is a controlled, purposefully ignited fire. These have been "prescribed" in order to reduce hazardous fuel loads. The goal is to burn up lots of ground fuel so that if a wildfire is ignited, it will not spread as quickly.