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Taking the Pulse of PyroCumulus CloudsForest fires can burn large areas, but can also inject smoke into the upper troposphere/lower stratosphere (UT/LS), where stakes are even higher for climate, because emissions tend to have a longer lifetime, and can produce significant regional and even global climate effects, as is the case with some volcanoes. Large forest fires are now believed to be more common in summer, especially in the boreal regions, where pyrocumulus (pyroCu), and occasionally pyrocumuionimbus (pyroCb) clouds are formed, which can transport emissions into the UT/LS. A major difficulty in developing realistic fire plume models is the lack of observational data within fire plumes that resolves structure at a few 100 m scales, which can be used to validate these models. Here, we report detailed airborne radiation measurements within strong pyroCu taken over boreal forest fires in Saskatchewan, Canada during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) summer field campaign in 2008. We find that the angular distribution of radiance within the pyroCu is closely related to the diffusion domain in water clouds and can be described by very similar simple cosine functions. We demonstrate with Monte Carlo simulations that radiation transport in pyroCu is inherently a 3D phenomenon and must account for particle absorption. However, the simple cosine function promises to offer an easy solution for climate models. The presence of a prominent smoke core, defined by strong extinction in the UV, VIS and NIR, suggests that the core might be an important pathway for emission transport to the upper troposphere and lower stratosphere. We speculate that this plume injection core is generated and sustained by complex processes not yet well understood, but not necessarily related directly to the intense fires that originally initiated the plume rise.
Document ID
20120009494
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Gatebe, C. K. (Universities Space Research Association Columbia, MD, United States)
Varnai, T. (Maryland Univ. Baltimore County Baltimore, MD, United States)
Poudyal, R. (Science Systems and Applications, Inc. Lanham, MD, United States)
Ichoku, C. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
King, M. D. (Colorado Univ. Boulder, CO, United States)
Date Acquired
August 25, 2013
Publication Date
January 1, 2012
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC.JA.6091.2012
Funding Number(s)
CONTRACT_GRANT: NNX11AQ98G
CONTRACT_GRANT: NNX08A89G
Distribution Limits
Public
Copyright
Public Use Permitted.

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