Why isn't the Seattle area more polluted? (Vancouver, Everett: bars, air pollution)

[TheTimidBlueBars]

Seems like pollution is mostly a western US thing (LA, Bay Area, SLC, Las Vegas etc.) due to mountain ranges trapping clouds of particulate matter. Seattle is also hemmed in by the Olympics and the Cascades; why isn't it more polluted?

I moved down to the Bay Area in July, and I've been noticing myself coughing more the past couple months. I typically wear a mask outside now and that really helps.

[Ruth4Truth]

Originally Posted by TheTimidBlueBars

Seems like pollution is mostly a western US thing (LA, Bay Area, SLC, Las Vegas etc.) due to mountain ranges trapping clouds of particulate matter. Seattle is also hemmed in by the Olympics and the Cascades; why isn't it more polluted?

I moved down to the Bay Area in July, and I've been noticing myself coughing more the past couple months. I typically wear a mask outside now and that really helps.

Puget Sound actually is fairly polluted, but it's an invisible type of pollution (some of it--illegal), so it's not well known. You're talking about air pollution, though. Seattle isn't that hemmed in. The Cascades are farther away than LA's mountains are from LA. Plus, there are no mountains to Seattle's north; it's free and clear northward into British Columbia. There's also air circulation coming in from the ocean via the Straight of Juan de Fuca, and there's open water to Seattle's west/northwest over to Vancouver Island, which does have a mountain ridge, but not of the magnitude or elevation of the Olympics or Cascades.

Also, I don't think the Seattle area has that much industry spewing pollution into the air. At this point, I would think vehicle exhaust may be the main air pollutant.

I also question how polluted the Bay Area air is. It's never been comparable to LA's air pollution, especially back before the state instituted burning bans of various types to improve LA's air. But the Bay Area also has no mountain range to its north, and only a ridge of hills on its east side. The pollution blows eastward over the Central Valley and gets hung up on the Sierra Mountains, affecting the air quality in the foothills.

LA is fairly unique on the W Coast in how its mountains are closer in, and tend more to encircle it.

[homesinseattle]

Originally Posted by TheTimidBlueBars

Seems like pollution is mostly a western US thing (LA, Bay Area, SLC, Las Vegas etc.) due to mountain ranges trapping clouds of particulate matter. Seattle is also hemmed in by the Olympics and the Cascades; why isn't it more polluted?

I moved down to the Bay Area in July, and I've been noticing myself coughing more the past couple months. I typically wear a mask outside now and that really helps.

You are right Timid, the air quality in the Seattle area is pretty good for the size city it is, except of course during summer fire season. First, we aren't a very "industry heavy" city. Though we certainly have some auto pollution, weather systems usually come in with clean air from the west (Pacific Ocean) and prevailing winds wash the city accumulated pollution to the east, over and around the Cascade Mountains. Unlike LA, it certainly helps that our mountains don't start for awhile east of Seattle.

[rjshae]

The air here used to be more polluted during the summer months, but the vehicle emissions requirements have cleaned a lot of that up. I suspect that has also helped some of the wildlife around here recover as well. The biggest pollutant now seems to be the wildfires, which are getting worse on average.

[CrazyDonkey]

Puget Sound and the Salish Sea do form a "basin" of sorts, but with multiple passages, in and out, for air. Typically, we might have colder air coming down from the north, through the Strait of Juan de Fuca or the Frazer River Valley, meeting warmer air flowing in from the Pacific, around the Olympics, and up from the south, forming the Puget Sound Convergence Zone roughly between Seattle and Everett, creating a band of precipitation, cleaning the air.

Where we can get stagnant air is when hot (often "smokey") air flows through the passes from Eastern Washington and into the Puget Sound Basin, where it can be trapped by cooler marine flows from the Pacific.

[grega94]

I think it has to do the Seattle’s long rainy season, the particulates get washed out. During long dry periods the air can get pretty stagnant and accumulate pollution.

[Ruth4Truth]

Originally Posted by CrazyDonkey

Puget Sound and the Salish Sea do form a "basin" of sorts, but with multiple passages, in and out, for air. Typically, we might have colder air coming down from the north, through the Strait of Juan de Fuca or the Frazer River Valley, meeting warmer air flowing in from the Pacific, around the Olympics, and up from the south, forming the Puget Sound Convergence Zone roughly between Seattle and Everett, creating a band of precipitation, cleaning the air.

Where we can get stagnant air is when hot (often "smokey") air flows through the passes from Eastern Washington and into the Puget Sound Basin, where it can be trapped by cooler marine flows from the Pacific.

It's the Straight of Georgia that brings the cold air from the north, and the Straight of Juan de Fuca that brings it in from the Pacific.

[CrazyDonkey]

Originally Posted by Ruth4Truth

It's the Straight of Georgia that brings the cold air from the north, and the Straight of Juan de Fuca that brings it in from the Pacific.

By tonight at 10 PM, much colder air moves into southern BC (while shades), and cooler air pushes through the Fraser River valley north of BC and into NW Washington.

https://cliffmass.blogspot.com/2022/...push-into.html

https://cliffmass.blogspot.com/2009/...-gap-wind.html

[Thealpinist]

Originally Posted by TheTimidBlueBars

Seems like pollution is mostly a western US thing (LA, Bay Area, SLC, Las Vegas etc.) due to mountain ranges trapping clouds of particulate matter. Seattle is also hemmed in by the Olympics and the Cascades; why isn't it more polluted?

I moved down to the Bay Area in July, and I've been noticing myself coughing more the past couple months. I typically wear a mask outside now and that really helps.

Vigorous Progressive weather systems off the North Pacific keeps the air cleaner. Also keep in mind Seattle doesn’t really sit in a bowl. Although Seattle has the Olympics to the west and Cascades to the east. Storm systems are able to split around the Olympic mountains which in turn leads to less stagnation. Seattle is also not immediately down wind of any significant sources of air pollution.

San Francisco does not have the benefit of storm systems circulating out of the Gulf of Alaska. Salt Lake City is practically a desert and doesn’t get much precipitation. It also sits in a giant bowl that doesn’t allow any particulate matter to escape.

Seattle is fortunate indeed.

[NW4me]

Originally Posted by grega94

I think it has to do the Seattle’s long rainy season, the particulates get washed out.
During long dry periods the air can get pretty stagnant and accumulate pollution.

Also, Seattle doesn't get as much sunshine as most Western cities,
and sunlight actually plays a part in creating some air pollutants:
http://www.sciencedirect.com/topics/...ochemical-smog