2023 Exceptional Events

2023 Exceptional Events for Ozone

During 2023, Connecticut was impacted by wildfire smoke, mostly from historic fires from western Canada and Quebec. Besides raising PM2.5 to record levels, the smoke also produced ozone in excess of normal levels. This necessitated the drafting of an exceptional event request to exclude several days of monitored ozone from regulatory determinations.

June 7, 2023 Satellite Image

This satellite image above shows the extent of the Quebec wildfire smoke plume on June 7, 2023.

The aerosol optical index (AOD) is a derived satellite product that shows the presence and intensity of aerosols and is useful for tracking smoke plumes. Satellite AOD plumes, mainly from Canadian wildfires, are observed every day in this animation from May- September 2023.

Prior to the June Quebec fires, several wildfires were blazing in Nova Scotia, Canada in late May 2023. Smoke from these fires in Nova Scotia blew over Connecticut and then recirculated over the area during June 1-2. This contributed to elevated ozone levels, before a cold front passed through late on June 2nd. Here is the link to a satellite animation for May 31- June 2, 2023 showing the smoke over our region. This smoke event did not meet the criteria for an exceptional event.

The following image on June 2nd shows the location of the newly ignited Quebec fires and their smoke plumes that would bring us the worst air quality for PM2.5 ever recorded. Note that the winds were such that these smoke plumes would travel south and blanket the east coast for several days.

June 2, 2023 Satellite Image of smoke plumes

Exceptional Events Demonstration

Because of the persistent smoke impacting ozone levels in Connecticut during 2023, it was decided to pursue an exceptional events demonstration for monitors of 'regulatory significance', according to the EPA Guidance on the Preparation of Exceptional Events Demonstrations for Wildfire Events that May Influence Ozone Concentrations. Regulatory status is determined by calculating a design value using monitored data and comparing it to the 8-hour ozone NAAQS (70 ppb). Only monitoring sites whose design values affect the ozone attainment status in that non-attainment area are considered to have regulatory significance.

The following events and locations are the subject of this exceptional events request based on their regulatory significance for the Greater Connecticut ozone non-attainment area: Cornwall, East Hartford and Groton.

April 13-14

June 30-July 1

July 12