- Title
- Statistical assessment of Australian bushfire conditions : long-term changes and variability
- Creator
- Biswas, Soubhik
- Date
- 2023
- Type
- Text; Thesis; PhD
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/194055
- Identifier
- vital:18293
- Abstract
- In the wake of increasing bushfire impacts in recent decades across the Australian landscape, questions arise regarding the role played by weather conditions, climate variability and long-term climate change. This thesis seeks to quantify the following components that can influence fire risk: (1) the effects of weather and mean climate conditions, (2) large-scale drivers of natural climate variability, (3) the influence of extreme weather events and (4) the contribution of long-term anthropogenic climate change. Bushfire risks associated with weather and climate factors in Australia are generally assessed using indices such as the Forest Fire Danger Index (FFDI). The FFDI is used in this study, calculated from daily values of rainfall, relative humidity, temperature and wind speed, providing a generalised approach for combining those four weather factors known to influence fire behaviour. This study also aims to fill several knowledge gaps in the literature. For example, a comprehensive study of climatology, variability and trends in Australia's fire weather conditions was never attempted before using a high-resolution and a very long-term fire weather dataset. The fire weather conditions were analysed using a long-term FFDI dataset constructed from 20th Century reanalysis climatic data with bias correction applied because reconstructed weather datasets like 20th Century reanalysis products often show systemic biases. Various statistical bias correction approaches based on quantile-quantile matching were compared, and a spline-based method was selected due to its higher precision in correcting a distribution for the purposes of this study. The relationship of this calibrated FFDI dataset with the climate drivers of El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Southern Annular Mode (SAM) and Interdecadal Pacific Oscillation (IPO) was analysed. Results are mapped to show the regional and seasonal fluctuations in the severe fire weather across Australia during different combinations of ENSO, IOD, and SAM phases. During the austral spring and summer seasons, the highest frequency of severe fire weather conditions occurred for the combination of positive ENSO (i.e., El Nino), positive IOD and negative SAM. The calibrated FFDI dataset derived from bias-corrected Twentieth Century Reanalysis data was further used to study the long-term climate change trends in Australian fire weather conditions. A general positive trend in the number of extreme FFDI days was reported across Australia, except for New South Wales in Spring where a statistically non-significant negative trend was observed. Temperature and relative humidity were found to be the most critical climatic variables influencing fire weather trends across the country, noting that relative humidity is partly based on temperature. The applications of this work range from being useful for various stakeholders in framing new climate change adaptation policies to being used for seasonal outlooks and planning by fire management teams.; Doctor of Philosophy
- Publisher
- Federation University Australia
- Rights
- All metadata describing materials held in, or linked to, the repository is freely available under a CC0 licence
- Rights
- Copyright Soubhik Biswas
- Rights
- Open Access
- Subject
- Bushfire; Forest fire; FFDI; ENSO; IOD; SAM; IPO; Trend,; Variability
- Full Text
- Thesis Supervisor
- Chand, Savin
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