Surface air quality near sea level has been relatively good over the western lowlands this summer, even when wildfire smoke was evident aloft.
Consider the visible satellite picture this morning (see below). There are low clouds over the coast and western Washington and much smoke over much of the region.
Last evening I was flying home from a meeting in Washington DC; an upper-level smoke layer was evident in the sunset while I was landing. indicated by the familiar reddish glow produced by smoke:
With all this smoke floating around, air quality has remained quite good at low levels around western Washington. This situation is illustrated by the 4 PM air quality map showing the concentrations of small particles ( PM2.5). Lots of green (good air quality) in the west. Air quality degrades (yellow) in the mountains and worsens further (red) over the Columbia Basin. The major "smoker" at this time is the William Mine fire near Mt. Adams (several red dots). Smoke is also reaching our area from fires in the central/southern Oregon Cascades and from Canada.
Importantly, our air quality is holding pretty well. The reason is that the smoke from distant fires is staying aloft. To prove this, here is a view of the smoke over Seattle over time using a device called a ceilometer, owned by the Puget Sound Clean Air Agency, a group I work with very closely.
Height about the surface is on the Y-axis and time is on the X-axis, increasing to the right. Yesterday and this morning is being shown. This device can sense smoke and clouds aloft.
Yesterday a layer of smoke moved in aloft between 2000 and 4000 meters about the surface. Then some low clouds came in (the red line), obscuring what was above.
The smoky air stayed aloft because there was relatively cool, dense air near the surface over western Washington....heavy, dense air near the surface suppresses mixing in the vertical.
But during the day, as the surface heats up, vertical mixing increases, bringing some smoky air down to the surface. That happened today at well (see plots of surface particulates in Seattle below). Still quite modest levels of particles.
As I mentioned, this has been a relatively benign summer for surface air quality from smoke over the lowlands. To show this, here is a plot of small particle concentrations for stations in King County from January 1 to today. 50 and above is moderate to poor air quality.
The big spike was July 4th! You will notice a small rise during the past week, but still quite modest levels. Air quality was generally poorer during January and that was not from wildfire smoke, but rather from wood stoves and the like.
With cooling temperatures and the potential for rain next weekend, I suspect western Washington surface air quality should remain fine the rest of this month
Pleasant summer this year for a change. Seems to be more of what I remember Northwest summers were like growing up. A little rain, a bit of heat, high smoke, unremarkable in every way.
ReplyDeleteI guess it depends on when you grew up in the Northwest. I grew up in Seattle in the 1930s to about 1960 and have lived in the Wenatchee area since, and in those earlier days in Seattle, smoke of any kind was rare. It was even rare in the Wenatchee area up to about 20 or 25 years ago but now seems almost a yearly thing.
DeleteInterestingly enough, if you were 30 years older you would have remembered a far more smoky time. Historically, the NW was a very smoky place during mid to late summer. Folllowed by the suppression period of your youth....cm
DeleteI am sure it was smokier in the early 1900s and before since there was lots of uncontrolled fire due to land clearing and railroad fires besides lightning fires and very little in the way of suppression efforts. Suppression efforts in the more recent years when I was growing up probably helped reduce smoky days but also coincided with less severe fire seasons weather wise. We have had as much and possibly even better fire suppression in recent years, yet many more smoky seasons than when I was growing up, which I believe is due mainly to more frequent severe weather related fire seasons.
DeleteOur minds play tricks on us and one's memory of what the weather was like decades ago isn't going to be accurate. If you look at the tables Cliff often includes in many of his posts, you'll see things haven't actually changed enough to make a noticeable difference.
DeleteJHK, here we are talking about the amount of smoke present at various times in the past. If Cliff has posted a table showing this through past years back to the early 1900s, I haven't seen it. Please point it out to me. I have followed weather conditions closely since I was young and I think I have a pretty good memory of what conditions were like even that long ago, and certainly in recent times.
DeleteWhile the air quality this month hasn't been particularly bad in the Bellingham area by the standards of recent summers, it's been significantly worse than the first 3rd of last August. The average AQI for the month to date at my location is about 30, while for 8/1-10/23 it was about 14. The worst air quality day of the month to date was 8/9 with an average AQI of about 66, while the worst air quality day during the first 10 days of last August was, coincidentally, also 8/9 - but with a noticeably lower (better) average AQI of about 28.
ReplyDeleteThe difference is certainly correlated with the fact that wildfire acreage burned in Washington during 2023 was significantly less than this year. Wildfire acreage burned so far this year is already about 100,000 acres more than had burned by early October during 2023.
Lightning in the mountains west of Ellensburg on August 9 started 13 fires in the Okanogan-Wenatchee National Forest. The Kittitas Valley had a lot of smoke, but near the ground there was no smoke smell. The satalitte image from Aug 10 at 1701 UTC shows this well. There were too many spot-sources to claim where my smoke came from.
ReplyDeleteThe fire near Mt. Adams is called the Williams Mine Fire. It and others are in this report:
FIRE REPORT: Williams Mine Fire expands rapidly | Columbia Basin Herald
Great blog Cliff, it's amazing to see how the thick marine layer that makes it to the cascade crest can dampen the fires. The much cooler past few days has sure been nice too
ReplyDeleteIs it me, or has this been abnormally high humidity lately? My weather station has been showing that we have been cycling from 50% at midday to 90% over night. When I wake up in the morning the carpets all feel damp.
ReplyDeleteWhile the AQI has been good, so particles > 2.5, the particle count for > 0.5 has been spiking at times when the NO2 levels have been high as well. The air quality certainly does not seem as ok as the AQI level indicates.
ReplyDelete