Smoke from fires can travel thousands of miles impacting weather, climate, and air quality

Prior posts have noted the impact of fires in Southeast Asia on air pollution throughout the region.

While it has been known for decades that large wildfires can create or enhance thunderstorm clouds, leading to what are called pyrocumulonimbus clouds ("pyroCbs"), only recently have researchers discovered that the clouds can boost smoke into the stratosphere.  Once in this layer of the atmosphere - immediately above the troposphere, where most of Earth's weather happens - the smoke can be caught by jet stream winds and carried long distances, impacting air quality thousands of miles from the origin of the smoke.

Along with aerosols, these plumes carry a heavy load of the chemically active gases that are produced in substantial quantities during a fire, especially in the smoldering phase.  While their chemical and climatic effects are not fully known, the plumes' dark particles tend to absorb sunlight, warming themselves and the atmosphere around them while cooling Earth's surface slightly.  A fuller understanding will help scientists fine-tune climate models, adjusting contributions from various aerosol sources.

Where pyroCbs differ from standard storm clouds in their source of convection.  While it's the heat produced by condensing water vapor that drives the updrafts in the towering thunderheads of cumulonimbus clouds, those in pyroCbs are largely driven by the intense heat of the wildfire at ground level.  That gives pyroCbs an extra push: The momentum from particularly strong updrafts enables the fire-fueled clouds to routinely make it to the lower reaches of the stratosphere.  Even the tops of typical cumulonimbus clouds, in contrast, rarely rise out of the troposphere.  Further, in addition to aerosols (such as smoke and soot), fire-fueled clouds inject unusually large quantities of chemically reactive gases such as carbon monoxide, methyl cyanide and hydrogen cyanide into upper layers of the atmosphere.  The effects and fate of these aerosols and gases is not well understood.

As a column of smoke rises from a wildfire, it pulls in surrounding humid air.  The moisture in that air condenses to form the pyroCb cloud as the plume reaches high altitudes.  It is unknown what happens inside these clouds, but satellite images clearly show that smoke carried upward inside the clouds emerges from the top as if from a chimney.

Data on this phenomenon needs to be better developed so that weather, air quality, and climate models can take them into account.

Further information on this phenomenon can be found at http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=table&application=ja10&convert=&converthl=&refinequery=&formintern=&formextern=&transquery=fromm&_lines=&multiple=0&descriptor=/data/epubs/wais/indexes/ja10/ja10|532|4449|The%20Untold%20Story%20of%20Pyrocumulonimbus%20(%3Ci%3EInvited%3C/i%3E)|HTML|localhost:0|/data/epubs/wais/indexes/ja10/ja10|31469%2035918%20/data2/epubs/wais/data/ja10/ja10.txt, http://journals.ametsoc.org/doi/abs/10.1175/2010BAMS3004.1. and http://adsabs.harvard.edu/abs/2009AGUFM.A51B0111L.