Improved Air Quality at Low Levels over Western Washington as Smoke Pours in Overhead: It Won't Last Long

The three dimensionality of the atmosphere over the Northwest is well-illustrated this morning, as cool, relatively clean marine air pushed into western Washington overnight, while smoke moved in overhead from fires in eastern WA and British Columbia.

The visible satellite image this morning says it all.  Low clouds cover the ocean, with some of them pushing inland to Olympia and through the Strait of Juan de Fuca.  Smoke covers eastern Washington and British Columbia and is pouring westward aloft over Northwest Washington and the Cascades.

To get an idea of the vast differences in local air quality (actually amounts of small particles in the air), here is plot from the wonderful Forest Service Airfire web site.  Green is good air quality, red is bad, and yellow is marginal.  Most of western Washington is now enjoying decent air quality near the surface due to the marine air intrusion last night.    Eastern Washington and BC are bad news.  On the right you can view plots at individual stations.  Big improvements in Seattle, Portland, and the coast.  Lots of smoke at Twisp and Ellensburg in eastern WA.

As I noted, the three dimensionality of the atmosphere is critical for understanding what is happening now.    Consider the winds and temperatures about Sea-Tac Airport over the past day (see below, time height cross section of winds and temperature, temps in °C, heights in pressure, 850 is about 5000 ft).   You can see shallow southwesterly winds bringing in cooler air (14C, 57F), while northeasterly/easterly winds are aloft.  We actually have an inversion right now above us, with temperatures warming with height until about 900 hPa (about 3000 ft)

The low level air is clean and cool, while the easterlies aloft are laden with smoke.   The smoke aloft is what is radically reducing the solar radiation reaching the surface and giving the sun's light a reddish color.  The smoke we are seeing is now partially domestic, with a major fire in the NE WA Cascades.

If you want to escape smoke, go south of Olympia or head to the coast.

Now the bad news.  Today is the good day for air quality around Puget Sound.  The onshore flow will weaken today and daytime mixing will bring the smoke down to the surface.  Tomorrow (Sunday), the winds will be more northerly, which will lessen the inland movement of clean Pacific air and bring more smoke down from BC.

Global Warming 

There are a number of folks that are claiming that this smoky/warm period is a sign of global warming.   I believe that many of them are seriously stretching the facts and trying to simplify a complex situation.  I will blog about this issue during the coming week, but consider the following:

1.   Most forest management experts agree that the major issue is the past mismanagement of our forests.   This includes suppressing natural fires, leaving slash and dead material on the forest floors, changing the density of the east-side forests, and much more.   Some global warming activists are happy to ignore this.
2.  Wildfire is a natural part of healthy forests in our region.
3.  The replacement of natural grasses by fire-prone foreign species has greatly increased grass fires.

4.  Increasing human pressure and fire initiation (fireworks, campfires, arson) has enhanced fires.
5.  The meteorological situation of this event is not one of uniform warming, but localized warming during the last month due to anomalous high pressure over our region.  The weather has been COOLER THAN NORMAL over the the high plains.  There is NO reason to expect more high pressure in the future under global warming.

Human-induced global warming has warmed the region about 1F so far, which is MUCH less than the 15-20F temperature anomalies associated with this event.

More later.

Smoke Starts to Recede as Marine Air Pushes into Western Washington

A weak inland push of marine air occurred this morning, resulting in dramatic improvements of air quality along the coast, in the Strait of Juan de Fuca and over the south Sound.   On the other hand, some locations over NE Washington have worsened smoke, as local fires have added to the plumes from British Columbia.  Seattle, located in the dead zone behind the Olympics, has not enjoyed much improvement yet...but the smoke will slowly lessen during the next day.

The NASA MODIS satellite imagery shows low clouds along the coast, with some tendrils moving inland through the coastal mountains.   Western Oregon and SW Washington are less smoky, but some smoke is still evident over Puget Sound.  Dense smoke is found over NE WA from a combination of the smoke from BC and local fires (e.g., the Diamond Creek fire).  Very bad over Bellingham and Vancouver.

 Compare today's MODIS image to yesterday's at the same time (around 1 PM).
More smoke over the offshore waters and SW Washington.  Better over NE WA.

Air quality has improved at several locations, but gotten worse at others. Here is the data, showing  a plot of the concentration of small particles (PM2.5).  Seattle (blue) is slightly better, but Aberdeen, Mount Vernon, and Cheeka Peak (NW tip of the Olympics) are almost back to normal.  In contrast, Twisp--in the eastern foothills of the North Cascades--is a disaster, with a huge spike in particles.

A solar radiation measuring device near Twisp indicated a LOSS of 70% of the normal radiation from the sun.  Unbelievable.

Improvement in western Washington is occurring as the thermal trough jumped into eastern WA and an onshore pressure gradient has developed, in turn forcing onshore winds.  You can see this trend from the winds above Seattle (see time0/eight cross section below, time on x axis, height in y).  Both winds (barbs) and temperature--red lines--are shown.  The strong northerly winds of the past few days are gone (which blew in the smoke), but the winds are too light to really mix out our smoky surface layer.

The forecasts model for tomorrow show a continuation of weak onshore flow...this will bring down temperatures (into the upper 80s, but still way above normal), but not enough to clean out the lower atmosphere of western WA.

We are simply not going to cool down much over the weekend.  The reason...an amazingly persistent ridge of high pressure over the West Coast (see map for Saturday afternoon at 500 hPa).  And folks, there is little doubt we are going to break the big record for consecutive dry days (51).