The smoky skies over Seattle are likely from Asia and not Western fires, says Cliff Mass, KPLU weather forecaster and University of Washington professor.
In his blog post on the smoke, he said the air over us can be traced back to Asia at low levels.
"This smoke is above the surface in the middle troposphere and is coming from the southwest. Examining the flow aloft it really appears unlikely to be coming from any of the western U.S. fires. ... In fact, some other modeling systems, such as one using output from ECMWF global model were suggesting the same thing – there are large areas of smoke over Asia that are moving our way."
Phil Swartzendruber with the Puget Sound Clean Air Agency says the Asian smoke is not posing any problems for human health.
“The conditions are really good for stuff making it over to us, but it tends to stay in the middle atmosphere and doesn’t really come down – and gets diluted as it comes down, so we never really get the full strength of it down at the ground.”
He says it can be seen though as haze on the horizon that decreases visibility and can cause the sun to appear redder than normal during sunrise and sunset. It can also affect ozone levels, which often become elevated during long stretches of sunny summer weather, but is not a concern in this current episode.
European Center for Medium Range Forecast biomass burning smoke prediction model is suggesting the same thing – there are large areas of smoke over Asia that are moving our way:
NASA video explaining how smoke from Asian fires reach us the Northwest:
http://www.youtube.com/watch?v=LE2vf7XVmKY&feature=youtube_gdata_player
About the above video: Research scientist Colin Seftor talks about images from the OMPS instrument on the Suomi NPP satellite. Suomi (NPP) launched in the fall of 2011. These images show smoke from Asia that migrates to North America. Seftor explains the importance of aerosols to the studies of climate as well as how critical it is to collect long term data records.
From a NASA press release in June:
Colin Seftor, an atmospheric physicist working for Science Systems and Applications, Inc. at NASA Goddard Space Flight Center, in Greenbelt, Md. studies aerosols using OMPS data and created images from them. "This smoke event is one example that shows that what happens over one area of the earth can easily affect another area thousands of miles away, whether it’s from Asia to North America or North America to Europe, and so on. Not only smoke and dust can get carried long distance. Pollutants, and even disease-carrying spores can be carried by the prevailing winds. For this event, I found out that the smoke plumes were lofted up to at least 12 kilometers (or about 7.5 miles) from the intense heat of the fires. At that point the smoke got picked up by higher level winds," Seftor says. Seftor false-colored the images to make the data stand out. He said," The colors on the image are artificial, but what they convey is a sense of the density of the smoke." In the images, he used blue and green colors to represent less smoke. Yellows and pink represent more smoke. Seftor showed smoke density by the level of transparency in the coloration. The less dense the smoke is the more you can see through it, and the more dense it is, the less you can see through it.
NASA photo(below): Hundreds of fires continued to burn in central Russia in early July, 2012, belching tremendous quantities of smoke across the region. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image of the smoke-laden skies on July 3.
Of course, the Asian smoke has made for some amazing sunsets:
