And we have had a good demonstration of this long-range transport during the past few days, as smoke from huge fires over southern Siberia have wafted across the North Pacific, producing hazy skies and enhanced sunsets/sunrises over the U.S. West Coast and western Canada.
We don't think about it very much, but the air we breath in Seattle today was over Asia 3-7 days ago.
Yesterday morning , I was walking with a friend along the Sound and the reduced visibility of Rainier and other features was striking. An image from the UW web cam yesterday afternoon illustrates this. Sunrises and sunsets have been accentuated with enhanced red colors--a good sign of smoke.
Western Asia has been an environmental problem zone the past week. The initiator of the problems was a strong low center that moved eastward over Siberia, producing strong winds over the region (see weather map with sea level pressure and 5000 ft above sea level wind speeds for 1200 UTC April 15th). The colors show wind speed and greens are winds about 40 knots.
Some farmers in Siberia prepare their fields by burning debris from the previous year and unfortunately the winds caused the fires to burn out of control, causing a massive conflagration that has killed at least 30 people, destroyed thousands of homes, and created a huge smoke plume.
The same strong winds have picked up dust and sand in Mongolia and northern China, resulting in one of the worst dust /sand storms around Beijing in years.
NASA satellites have documented both the fires and the smoke/dust rising up over Asia and have tracked it crossing the Pacific. This image from April 14th shows the fires and if you look closely you will see the smoke plumes (greyish shading in contrast to the clouds, which are more white).
Here are a sequence of NASA images showing clouds and the smoke (colored), starting over Asia and moving our way. You can see the substantial value of NASA satellites that observe our atmosphere at many wavelengths, showing everything from clouds and precipitation particles to aerosols and pollution.
Not convinced of the Asian origin of our air the last few days? Well, to confirm the above hypothesis I ran an air trajectory model (NOAA Hysplit) to see where the air over us come from.
Specifically, I found the origin of the air at 11 AM Saturday ending over Seattle at three levels: 1000, 2000, and 3000 meters above sea level (shown by red, blue, and green lines in the figure). Our air came from Asia, with the air ending at 3000 meters above us (roughly 10,000 ft) starting OVER SOUTHERN SIBERIA.
Air quality data at the surface over our region has shown little impact, suggesting most of the Asian smoke has stayed aloft.