Investigating the Effect of Fuel Moisture and Atmospheric Instability on PyroCb Occurrence over Southeast Australia

The incidence of pyro-cumulonimbus (pyroCb) caused by extreme wildfires has increased markedly in Australia over the last several decades. This increase can be associated with a dangerous escalation of wildfire risk and severe stratospheric pollution events. Atmospheric and fuel conditions are impor...

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Bibliographic Details
Published in:Atmosphere 2023-07, Vol.14 (7), p.1087
Main Authors: Ma, Wenyuan, Wilson, Caleb S., Sharples, Jason J., Jovanoski, Zlatko
Format: Article
Language:English
Subjects:
Aerosols
Air temperature
Atmospheric effects
atmospheric instability
Clouds
Environmental aspects
Environmental risk
extreme wildfire
Forest & brush fires
fuel moisture
Fuels
Humidity
Investigations
Lapse rate
logistic regression
Logit models
Moisture
Moisture content
Moisture effects
Moisture index
Ozone
Pollution
Probability theory
pyroCb
Statistical analysis
Stratosphere
Summer
Wildfires
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Summary:The incidence of pyro-cumulonimbus (pyroCb) caused by extreme wildfires has increased markedly in Australia over the last several decades. This increase can be associated with a dangerous escalation of wildfire risk and severe stratospheric pollution events. Atmospheric and fuel conditions are important influences on pyroCb occurrence, but the exact causal relationships are still not well understood. We used the Continuous Haines Index (C-Haines) to represent atmospheric instability and the Fuel Moisture Index (FMI) to represent fuel moisture to provide better insight into the effects of atmospheric and fuel conditions on pyroCb occurrence over southeast Australia. C-Haines and FMI were related to the probability of pyroCb occurrence by employing a logistic regression on data gathered between 1980 and 2020. Emphasis is placed on investigating the independent effects and combined effects of FMI and C-Haines, as well as assessing their potential to predict whether a pyroCb develops over a fire. The main findings of this study are: (1) high C-Haines and low FMI values are representative of favorable conditions for pyroCb occurrence, but C-Haines can offset the effect of FMI—the addition of C-Haines to the logistic model muted the significance of FMI; (2) among the components of C-Haines, air temperature lapse rate (CA) is a better predictor of pyroCb occurrence than the dryness component (CB); (3) there are important regional differences in the effect of C-Haines and FMI on pyroCb occurrence, as they have better predictive potential in New South Wales than in Victoria.
ISSN:2073-4433
2073-4433
DOI:10.3390/atmos14071087