Surface air quality near sea level has been relatively good in the western lowlands this summer, even as wildfire smoke remains visible aloft.
Take a look at the satellite imagery seen this morning (see below). There are low clouds over the coast and western Washington and a lot of smoke over much of the area.
Last night, as I was flying home from a meeting in Washington DC, I saw a layer of smoke high up in the sky during sunset as I was landing. This was indicated by the familiar red glow the smoke created:
With all this smoke, air quality remains fairly good, low in western Washington.
This situation is illustrated by the 4 p.m. air quality map showing concentrations of fine particulate matter (PM2.5). Lots of green (good air quality) in the west. Air quality is poor (yellow) in the mountains and worse (red) over the Columbia Basin. The biggest “smoke” right now is the Mineral Creek Fire near Mt. Adams (many red dots). Smoke is also coming to our area from fires in the central/southern Oregon Cascades and from Canada.
The important thing is that our air quality is still pretty good. The reason is that smoke from distant fires is still high up. To prove this, here is a time-lapse image of smoke over Seattle using a device called an altimeter, owned by the Puget Sound Clean Air Agency, a group I work very closely with.
Height above the surface is on the Y axis and time is on the X axis, increasing to the right. Yesterday and this morning are shown. This device can sense smoke and clouds above.
The smoky air remains aloft because there is relatively cool, dense air near the surface in western Washington….the heavy, dense air near the surface prevents vertical mixing.
But as the surface warms during the day, vertical mixing increases, bringing some of the smoky air down to the surface. That happened today (see the surface particle charts for Seattle below). Still pretty modest particle levels.
As I mentioned, this has been a relatively benign summer for surface air quality due to smoke over the lowlands. To show this, here is a chart of fine particle concentrations for stations in King County from January 1st through now. 50 and above is moderate to poor air quality.
The peak was July 4th! You’ll see a small increase over the past week, but it’s still pretty modest. Air quality is generally worse in January, and that’s not because of wildfire smoke, but because of wood stoves and the like.
With cool temperatures and a chance of rain next weekend, I suspect surface air quality in western Washington will remain good through the rest of this month.
