Thursday, August 1, 2013

Wildfires, Smoke, and Air Quality

Smoke from neighboring wildfires has severely impacted folks in Ashland and Medford, Oregon; in fact, several performances at the outdoor theaters at the famous Oregon Shakespeare Festival in Ashland have been cancelled the last few days for fear of endangering the health of actors and theater patrons.

As shown in this map of current major fires, several are located in southwestern Oregon.

Ashland and Medford often have poor air quality (and fog) in the winter because they lie in a topographic "bowl" that allows pollutants to concentrate (see map).   When an inversion builds over the basin, the build up is enhanced since inversions are very stable layers that act as a "lid."

And, in fact, on Thursday morning there was an inversion above Medford, as shown by the radiosonde launch at 5 AM (see graphic, red is temperature, blue is dewpoint).  An inversion is where temperature increases with height.  The numbers at the right are pressure (in hPa):   700 is about 10,000 ft, 850 is about 5000 ft.

A webcam from Oregon DOT along I5 in Ashland shows that the murk continued into this evening.

And the latest National Weather Service forecast for Ashland says it all:

The air quality measurements at Medford shows very high values of small particles in the air, with air quality being described as unhealthy to very unhealthy.

Here in Washington, the Colockum Tarps fire is still growing and spreading west and southward, approaching the wind turbines on Whiskey Dick Mountain east of Ellensburg (see the amazing picture below)

Air quality near this fire and the Mile Marker 28 fire near Satus Pass have declined substantially.  This graph compares the number of fine particles in the air at Seattle to Ellensburg and Toppenish (near Yakima).   You can see the impacts of the fires clearly.

There have been a lot of thunderstorms in eastern Washington and over the eastern slopes of the Cascades, as well as over eastern Oregon.  The winds from the thunderstorms helped reduce the air pollution in some areas, but the massive amount of lightning on Thursday could well have started more fires.  Time will tell.

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