Laboratory and numerical modeling of the formation of superfog from wildland fires
Document Type: Journal
Author(s): Christian Bartolome ; Marko Princevac ; David R. Weise ; Shankar M. Mahalingam ; Masoud Ghasemian ; Akula Venkatram ; Henry Vu ; Guillermo Aguilar
Publication Year: 2019

Cataloging Information

  • CCN - cloud condensation nuclei
  • liquid water content
  • superfog
  • visibility
Record Maintained By:
Record Last Modified: April 23, 2019
FRAMES Record Number: 57724


Smoke from human-induced fires such as prescribed fires can occasionally cause significant reduction in visibility on highways in the southern United States. Visibility reduction to less than three meters has been termed 'superfog' and environmental conditions that lead to its formation have been proposed previously. Accurate characterization and prediction of precursor conditions for superfog is needed to prevent dangerous low visibility situations when planning prescribed fires. It is hypothesized that extremely hygroscopic cloud condensation nuclei from the smoldering phase of a fire can produce a large number of droplets smaller in size than in naturally occurring fog. This large number of small droplets can produce superfog conditions with relatively low liquid water content. A thermodynamics-based model for fog formation was developed. Laboratory generated superfog measured by a Phase Doppler Particle Analyzer determined that mean droplet radius was 1.5 μm and the size distribution could be modeled with a lognormal distribution. Experiments in an environmentally-conditioned wind tunnel using longleaf pine (Pinus palustris Mill.) needle fuel beds provided visibility, heat flux, temperature, humidity, and particle data for model validation. Numerical modeling was used to approximate the growth of a superfog boundary-layer with liquid water content values of 2 g m−3 or greater. The model successfully predicted previous superfog events.

Online Link(s):
Bartolome, Christian; Princevac, Marko; Weise, David R.; Mahalingam, Shankar M.; Ghasemian, Masoud; Venkatram, Akula; Vu, Henry; Aguilar, Guillermo. 2019. Laboratory and numerical modeling of the formation of superfog from wildland fires. Fire Safety Journal online early.