Local and regional smoke impacts from prescribed fires
Other literature type
Price, Owen F.
(issn: 1684-9981, eissn: 1684-9981)
Smoke from wildfires poses a significant threat to affected communities.
Prescribed burning is conducted to reduce the extent and potential damage of
wildfires, but produces its own smoke threat. Planners of prescribed fires
model the likely dispersion of smoke to help manage the impacts on local
communities. Significant uncertainty remains about the actual smoke impact
from prescribed fires, especially near the fire, and the accuracy of smoke
To address this uncertainty, a detailed study of smoke dispersal was
conducted for one small (52 ha) and one large (700 ha)
prescribed fire near Appin in New South Wales, Australia, through the use of
stationary and handheld pollution monitors, visual observations and rain
radar data, and by comparing observations to predictions from an atmospheric
dispersion model. The 52 ha fire produced a smoke plume about 800 m
high and 9 km long. Particle concentrations (PM<sub>2.5</sub>) reached very
high peak values (> 400 µg m<sup>−3</sup>) and high 24 h average
values (> 100 µg m<sup>−3</sup>) at several locations next to or within ∼ 500 m downwind from the fire, but low levels
elsewhere. The 700 ha fire produced a much larger plume, peaking at
∼ 2000 m altitude and affecting downwind areas up to 14 km
away. Both peak and 24 h average PM<sub>2.5</sub> values near the fire were lower than for the 52 ha fire, but this may be because the monitoring locations
were further away from the fire. Some lofted smoke spread north against the
ground-level wind direction. Smoke from this fire collapsed to the ground
during the night at different times in different locations. Although it is
hard to attribute particle concentrations definitively to smoke, it seems
that the collapsed plume affected a huge area including the towns of
Wollongong, Bargo, Oakdale, Camden and Campbelltown
(∼ 1200 km<sup>2</sup>). PM<sub>2.5</sub> concentrations up to
169 µg m<sup>−3</sup> were recorded on the morning following the fire.
The atmospheric dispersion model accurately predicted the general behaviour
of both plumes in the early phases of the fires, but was poor at predicting
fine-scale variation in particulate concentrations (e.g. places 500 m
from the fire). The correlation between predicted and observed varied between
0 and 0.87 depending on location. The model also completely failed to predict
the night-time collapse of the plume from the 700 ha fire.
This study provides a preliminary insight into the potential for large
impacts from prescribed fire smoke to NSW communities and the need for
increased accuracy in smoke dispersion modelling. More research is needed to
better understand when and why such impacts might occur and provide better
predictions of pollution risk.