A few days ago, I posted a few comments about a new article [de Laat et al. (2012)] on the spread of the smoke plume generated by the 2009 Black Saturday Bushfires in Australia. Now, there is a relatively new article on the long-range transport of smoke from boreal forest fires in western Canada into the eastern United States.
In a recent issue of Journal of Geophysical Research — Atmospheres, David Miller of Princeton University and colleagues from Princeton, Université de Lille, NASA, and NOAA tracked the eastward migration and subsequent air quality effects of smoke emanating from the 4 July 2006 forest fires in British Columbia, Yukon Territory, Alberta, and Saskatchewan. The authors analyzed a trove of satellite-based and ground-based observations and determined that the plumes from those moderate-intensity fires escaped from the atmospheric mixed layer and, once aloft, encountered the much stronger winds of the free troposphere, which eventually ferried them far to the east. They concluded that the remnants of the smoke plumes reached the east coast of the United States within days and then encountered downwelling air currents associated with a high pressure system that had blanketed the region. The subsiding air pushed the smoke back down into the lower troposphere, effectively fumigating the eastern seaboard with aerosols and chemically reactive gases that were originally belched out by the fires thousands of kilometers away.
Why is this important? When the particle-laden smoke plumes descended on the eastern seaboard, they increased the atmospheric concentration of fine particulates with diameters less than 2.5μm. Inhalation of fine particulates can have deleterious effects on human health. Furthermore, the researchers note that although the strongest, most intensely pyroconvective forest fires — say, those occurring once per decade or so — have been reasonably well-studied and are known to dump their combustion products thousands of kilometers away, there is a severe shortage of data on more modest-sized fires. Miller et al. (2011) show that modest size fires, like their larger cousins, can affect air quality even thousands of kilometers away and are thus worthy of more intensive study.
1. Miller, D. J., K. Sun, M. A. Zondlo, D. Kanter, O. Dubovik, E. J. Welton, D. M. Winker, and P. Ginoux, 2011: Assessing boreal forest fire smoke aerosol impacts on U.S. air quality: A case study using multiple data sets, J. Geophys. Res., 116, D22209, doi: 10.1029/2011JD016170 .