The Chisholm firestorm: observed microstructure, precipitation and lightning activity of a pyro-cumulonimbus

By Daniel Rosenfeld, M. Fromm, Jörg Trentmann, Gunnar Luderer, M. Andreae, R. Servranckx. 2006

162 citations recorded by the source corpus.

A fire storm that occurred on 28 May 2001 and devastated the town of Chisholm, ~150 km north of Edmonton, Alberta, induced a violent fire-invigorated cumulonimbus cloud. This pyro-cumulonimbus (pyro-Cb) had overshooting tops of 2.5–3 km above the tropopause, and injected massive amounts of smoke into the lower stratosphere. Fortunately, this event occurred under good coverage of radar, rain gauge, lightning and satellite measurements, which allowed in-depth documentation of the event, and gave us an opportunity to study the cloud top morphology and microstructure, precipitation and cloud electrification of the pyro-Cb. The combination of heat and smoke created a cloud with extremely small drops, which ascended rapidly in violent updrafts. There appeared to be little freezing up to the homogeneous freezing isotherm level of −38°C. A cloud with such small and short-lived highly supercooled drops is incapable of producing precipitation except for few large graupel and hail, which produced the observed radar echoes and charged the cloud with positive lightning. The small cloud drops froze homogeneously to equally small ice particles, for which there is no mechanism to aggregate into precipitation particles, and which hence remain in the anvil. The lack of significant precipitation implies that only a small fraction of the smoke is scavenged, so that most of it is exhausted through the anvil to the upper troposphere and lower stratosphere. Comparisons with other cases suggest that a pyro-Cb does not have to be as violent as the Chisholm case for precipitation to be strongly suppressed. However, this level of convective vigor is necessary to create the overshooting updraft that injects the smoke into the lower stratosphere.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/87f5ebf54345275cbac67b7b8d40ce9c415cce07

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In Astronomy and Astrophysics

M. Andreae

In Global and Planetary Change

Citations in the corpus

Aerosol- and updraft-limited regimes of cloud droplet formation: influence of particle number, size and hygroscopicity on the activation of cloud condensation nuclei (CCN) (2009, background): “…the extraordinary dynamical and microphysical properties of deep pyro-clouds (e.g. Fromm and Servranckx, 2003; Fromm et al., 2005; Trentmann et al., 2006; Rosenfeld et al., 2007) and their ability to transport substantial amounts of aerosol into the UT/LS (Fromm et al., 2005; Luderer et al., 2007).”
Depolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke (2018, background): “Within cumulus towers, enormous amounts of smoke can be injected into the upper troposphere and lower stratosphere (Fromm and Servranckx, 2003; Fromm et al., 2010; Rosenfeld et al., 2007; Peterson et al., 2017).”