September 18, 2011
As we move into fall, air quality events quiet down over the US
Today, few areas of the US are in the moderate AQI range (left) with the predominance of them having ozone reaching the yellow or moderate range in California (right image, RGB with AQI and Fire Locations overlaid). Otherwise, air quality is good across the nation with spot fires continuing to generate localized smoke.
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While it may look like there is haze in the midwest in the US RGB, this is actually an artifact in the Terra MODIS imagery. As we pointed out over a year ago, MODIS is now that old car that you love but doesn't quite work the way it did when it came out of the showroom. The right side of the image swath is much "bluer" than it used to be and this looks like haze when it is just an artifact of the radiometry. To show how dramatic it can be, I took a part of the image over California where the two passes are 1.5 hours apart. Clearly, the left (westernmost) side of the swath has truer colors than the right side of the swath (which is at the top left in this image).
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The largest fires (Pagami Creek in Minnesota, 41 Complex (Ravalli County) in Montana, and Dollar Lake (Hood River County) in Oregon) are still burning over tens of thousands of acres with less than 15% containment. Pagami has generated spectacular plumes of smoke and we were given data from Patrick Seifert in Leipzig, Germany (below) on September 16, which has shown that the Pagami plume has reached that continent. It started at over 12 kilometers altitude and was seen to penetrate the stratosphere. These "pyroCb" plumes are regularly observed and are the subject of the Yahoo pyroCb Listserve Group (you can follow the group on Yahoo Groups. Mike Fromm of NRL has found a CALIPSO cross-section over Europe which has caught the Pagami fire plume.
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Image courtesy Patrick Seifert, IfT, rights reserved.
And not to forget Texas, the three major fires there continue to burn although they are nearing containment (all are >90% contained).
Posted by Ray Hoff at September 18, 2011 6:14 PMSunrise here north of New York City seemed a bit rosy for a clear sky morning - caused by smoke aloft?
Posted by: Bob Kelly at September 19, 2011 8:50 AMPossibly, Bob. We will have to check lidar data from City College of New York. However, the GASP product doesn't show smoke. With the clouds moving in from the west, recall the old adage "Red sky at morning, sailors take warning. Red sky at night, sailors delight". That comes from overrunning cirrus to the east of large storms to your west.
Posted by: Ray Hoff at September 19, 2011 7:36 PM