TY - JOUR
T1 - Soot superaggregates from flaming wildfires and their direct radiative forcing
AU - Chakrabarty, Rajan K.
AU - Beres, Nicholas D.
AU - Moosmüller, Hans
AU - China, Swarup
AU - Mazzoleni, Claudio
AU - Dubey, Manvendra K.
AU - Liu, Li
AU - Mishchenko, Michael I.
PY - 2014/7/1
Y1 - 2014/7/1
N2 - Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimensionD f ≈1.8 mobility diameterD m ≤1 μm, and aerodynamic diameterD a ≤ 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic D f ≈ 2.6,D m .>1 μm, andD a ≤300 nmthat form via the cluster-dense aggregation mechanism.Wepresent additional observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (D f ≈ 1.8) aggregates, and ≈90% more warming than the volume-equivalent spherical soot particles simulated in climate models.
AB - Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimensionD f ≈1.8 mobility diameterD m ≤1 μm, and aerodynamic diameterD a ≤ 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic D f ≈ 2.6,D m .>1 μm, andD a ≤300 nmthat form via the cluster-dense aggregation mechanism.Wepresent additional observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (D f ≈ 1.8) aggregates, and ≈90% more warming than the volume-equivalent spherical soot particles simulated in climate models.
UR - https://www.scopus.com/pages/publications/84903707515
U2 - 10.1038/srep05508
DO - 10.1038/srep05508
M3 - Article
AN - SCOPUS:84903707515
SN - 2045-2322
VL - 4
JO - Scientific reports
JF - Scientific reports
M1 - 5508
ER -