1. Daily Screening for Wildfire Impacts on Ozone using a Photochemical Model A Proposal to the Texas Near-Nonattainment Areas
Greg Yarwood
Sue Kemball-Cook
Ramboll Environ
March 20, 2017

2. The 2015 Ozone NAAQS and the Exceptional Event Rule
In 2015, the U.S. EPA promulgated a more stringent ozone NAAQS of 70 ppb
It is now more likely that background ozone due to natural sources can cause U.S. ozone monitors to exceed the NAAQS even when local emissions from human activities are minimal
Background ozone is not controllable
The Exceptional Events Rule1 addresses monitoring data influenced by natural and/or uncontrollable events
State must prepare a demonstration to EPA showing
Clear, causal relationship between the event and the monitored exceedance
The event was not reasonably controllable or preventable
The event was a human activity that is unlikely to recur at a particular location or was a natural event
In 2005, Congress provided the statutory authority for the exclusion of data influenced by “exceptional events” meeting specific criteria by adding section 319(b) to the Clean Air Act (CAA). To implement this 2005 CAA amendment, the EPA promulgated the Exceptional Events Rule (72 FR 13560, March 22, 2007).
1https://

3. The Exceptional Events Rule and Design Values
An exceedance or violation due to an exceptional event may be excluded from the calculation of the monitor’s ozone design value*
Can lower the design value and even change nonattainment status to attainment
Example:
Exceptional Event
4 Highest Values of Daily Maximum 8-hour Ozone
Ozone design values are the metric calculated for comparison with the NAAQS and are defined as the consecutive three year average of annual 4th highest maximum daily 8-hour average (MDA8) ozone concentration.
*Design value:  3-Year Average of 4th high daily max 8-hour ozone not to exceed 70 ppb per 2015 Ozone NAAQS

4. Wildfires and Ozone
Wildfires create plumes with enhanced PM, NOx and ozone
Plumes affect ozone locally and regionally via transport
Wildfires can be classified as exceptional events
Wildfires are the most likely exceptional event to affect East Texas ozone
Photochemical models can quantify wildfire influences on ozone
Can provide prompt alerts of fire impacts on ozone at a monitor when used as a screening tool that is run every day throughout the ozone season
(AP Photo/Gregory Bull)

5. Photochemical Model Exceptional Event Screening System
Ramboll Environ proposes to deploy a photochemical model exceptional event screening system for East Texas from March 1, 2018 through October 31, 2018 and March 1, through October 31, 2019
Two CAMx photochemical model runs will be made for each day during the ozone season. The two runs will be identical except:
One CAMx run with fire emissions
One CAMx run without fire emissions
The difference in ozone between the two runs, (CAMx ozone with fire emissions – CAMx ozone without fire emissions), is the ozone impact of the fire emissions
The system will run automatically on each day and provide modeling products to the NNAs, including a daily assessment of fire impacts on ozone at NNA regulatory monitors

6. Exceptional Event Screening System Deliverables
The screening system output/results will be made available via a password-protected modeling system website hosted by Ramboll Environ
Example model fire impact results shown in slides 10-12
Ramboll Environ will alert NNA staff and the NNA’s TCEQ technical liaison when a fire event affects a monitor in their area
For each participating NNA, Ramboll Environ will prepare a report documenting the results of the exceptional event screening modeling at the Area’s monitors
All days with fire influence at NNA regulatory CAMS will be identified and the magnitude of the fire influence on the daily maximum 8-hour average ozone will be reported
A list of days warranting further analysis as a potential exceptional event will be developed

7. Exceptional Event Screening System Cost
Cost to deploy and operate the screening system is $150,000 per year
Total cost for FY18-19 biennium is $300,000
Costs can be shared among the NNAs
Cost to each NNA depends on number of participating areas

8. Examples of Photochemical Model Wildfire Analysis Results
Animations in slides show only the ozone produced by fires
Ozone is produced by fires in California, New Mexico and Arizona. The ozone produced by the fires is blown east by the winds and affects the CAMS 12 monitor in El Paso during midday on June 21
Ozone produced by fires appears as green, yellow and red. Areas where fire emissions consume ozone are blue.
Ozone forms during the day and dissipates at night

9. How to Run the Animation on the Next Slide
Move your cursor to the bottom of the figure
A control bar will appear under the contour color bar
Start/stop the animation by clicking on the arrow at the left of the control bar
The smaller arrows on the right of the control bar can be used to step through the animation frame by frame
Regions colored green and red show where fire emissions increased ground level ozone, while blue regions show where fire emissions decreased ground level ozone
There is a time stamp at the top of each animation frame: _03
YearMonthDay__Hour

10. Impact of Fire Emissions on Ground Level Ozone: June 17-22
Animation of CAMx Ozone Modeling Results
Impact of Fire Emissions on Ground Level Ozone: June 17-22
CAMx model results showing: Ozone impact of fire emissions = CAMx ozone run with fire emissions – CAMx ozone run without fire emissions
CAMS 12
4 km Domain

11. Animation of CAMx Regional Ozone Modeling Results
Impact of Fire Emissions on Ground Level Ozone: June 17-22
CAMx model results showing: Ozone impact of fire emissions = CAMx ozone run with fire emissions – CAMx ozone run without fire emissions
CAMS 12
12 km Domain

12. Example of Fire Impact: El Paso CAMS 12 on June 21, 2015
Ozone in the CAMx runs with (blue) and without (green) fire emissions differs substantially on June 21, the day when fires affected CAMS 12
Magnitude of fire impact is shown in red and is plotted on the right axis
The CAMx run with fires had 7 ppb more ozone at 11 am (red line) than the CAMx run without fires
Model results show a clear, causal relationship between fire emissions and ozone at CAMS 12