A Super-Inversion Leads to Poor Air Quality over the Region

A number of locations around the Northwest are experiencing poor air quality.....with some locations rivaling the particle concentrations experienced during the recent wildfire events.

But it isn't wildfires this time.   It is woodsmoke plus a SuperInversion.  Puget Sound Clean Air Agency has a Stage 1 Burn Ban in place.

Let's start by looking at the air quality information from the PurpleAir network (below) this morning.  Green is good air quality, yellow is declining, orange is of concern, and red/purple is unhealthy.

Mediocre air quality in the south Sound, but seriously degrading air quality around Spokane, northeast WA, and around Bend Oregon.


The origin of the smoke is clear: mainly smoke from burning wood for warmth.  Parenthetically, a highly renewable energy source.  

Traditionally, the main air quality problem in the Northwest has been from wood smoke, not summer wildfires.  But woodsmoke has declined as an issue as more folks use natural gas fireplaces/heaters and air quality agencies (such as Puget Sound Clean Air Agency) promulgate and enforce burn bans during threatening situations.   More extensive use of natural gas has helped clean our winter atmosphere. And increasing costs of oil and gas have also stimulated the use of wood.

We are in a threatening situation now, as a strong inversion, with temperature increasing with height, has developed over our region.  Inversions are very stable features that act as lids on the lower atmosphere.

Above SeaTac Airport this morning at 7 AM, temperatures increased from 38-39F just above the surface (and even lower at the ground) to 49-50F around 2000 ft.  A strong low-level inversion.


At Quillayute, on the Washington coast, temperatures increased from 1 to 13C over a similar layer near the surface (see plot below).  That is about 22F warming in a few thousand feet.  Wow.  Mama Mia...that is a strong inversion!


So we have cold weather that stimulates folks to rev up the wood burning and an inversion that caps the lower atmosphere, allowing pollution levels to rise.

Why do we have such a strong inversion?    Blame the strong, persistent high-pressure indicates ridge over us (see upper-level map for this morning below).


A high produces sinking air aloft that prevents clouds from forming.  Without clouds, the surface can effectively emit infrared to space, cooling the surface.  Like having a refrigerator coil at the surface.

The sinking from the high aloft causes the air to compress and warm at middle elevations.  This helps rev up the inversion even more!

And our nights now are very long as well, allowing more surface cooling.

The future outlook?  Expect poor air quality conditions to continue (or even worsen) this week.



Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more