It’s the end of October, and while there are still some active fires, it looks like the rain is here to stay. We wanted to review the most recent smoke events and put this bushfire season in context compared to previous years.
Air Monitoring Ecology coordinator Jill Schulte compiled these useful maps to look at the frequency and duration of smoke events. Daily smoke polygons were used for the Hazard Mapping System (HMS) developed by the National Oceanic and Atmospheric Administration’s (NOAA) Office of Satellite and Product Operations.
These polygons use daily GOES satellite imagery to classify smoke density as light, medium or heavy. Polygons classified as heavy are more likely to indicate the presence of smoke at ground level. To make these maps, the heavy smoke polygons of HMS during the wildfire season were overlaid with 4 km grid cells, and the number of days that each grid cell (in any part of the grid cell) intersected a thick smoke polygon was counted.
The first map below shows the average number of heavy bushfire smoke days from 2015 to 2021 – you can really see how different parts of the state have been affected by bushfire smoke over the years, with some locations seeing an average of more than 20 days of bushfire smoke. Forest fires smoke every year.
The second map below only describes the number of days of intense bushfires in 2022 – you can easily locate active fires that have led to prolonged smoke trails in Western and Central Western Australia.
So how was 2022 measured?
Another way to put this wildfire season into context is to look at the number of Washington residents exposed to extended periods of unhealthy air compared to other recent smoke events.
The number of people exposed to unhealthy or worse air quality (mean daily PM2.5 >55 micrograms per cubic meter) in 2022 is comparable to smoke-filled days in 2017, 2018, and 2020.
One difference between 2022 and previous years is the duration of the smoke event. While the smoke lasted much longer than we hoped this year, the majority of Washington residents were exposed to unhealthy or worse air for less than 5 days. A small part of the state (those closest to active fires including the Darrington, Leavenworth and Wenatchee areas) were exposed to unhealthy or worse air for 10-14 days.
Finally we can look at the updated cumulative exposure chart for PM2.5. Last time we checked in early October, statewide average concentrations in 2022 were average compared to those in the past 10 years. A week of thick smoke has an effect – an updated analysis below shows that statewide average concentrations of PM2.5 are greater than most years in the past decade. 2022 cumulative average concentrations of PM2.5 as of 10/25/2022 only less than 2017And the 2018And the 2020Years when there were bigger fires or smoke that covered the entire state for weeks.