Australian fire weather variability using calibrated long-term reanalysis data

Abstract Spatiotemporal variability on multi-decadal time scales can be observed in weather conditions associated with wildfires. The climatic factors that drive this variability in fire weather conditions have been studied using bias-corrected 20th Century Reanalysis data of the mean state and extreme values of the McArthur Forest Fire Danger Index (FFDI) from 1876 to 2014. In particular, the association of this time series with the climate drivers of El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM) are analysed using several techniques. The potential for long-term changes in the relationships between the climate drivers and seasonal FFDI values is also explored by breaking the total time period into two epochs. Composite analysis was performed to separate the phases of ENSO, IOD and SAM (given their interrelationships) and determine which phase combinations influence severe fire weather conditions the most. The most severe fire weather conditions were observed during a specific combination of ENSO, IOD and SAM phases, with results mapped to show spatial and seasonal variations in this over Australia. Long-term changes in the relationships between fire weather conditions and the three climate drivers (ENSO, IOD and SAM) are documented. These findings are based on a longer time period than similar previous studies, intended to help contribute to the range of guidance available for long-range fire weather outlooks and enhanced decision-making for fire agencies.