Fig. 4: Southeast Australia fire weather magnitude and frequency variability from 1900-2020 and synoptic conditions the reconstruction is sensitive too.
From: Australia’s 2019/20 Black Summer fire weather exceptionally rare over the last 2000 years
a Late austral spring-summer (November to February) observed FFDI (Dowdy et al.28) and FFDI prediction (this study) over the forested east coast and alpine regions of southeast Australia using the LDsss record (refer to the hatched area in Fig. 5g for reconstruction region). Light grey shading represents 95% prediction interval of the FFDI mean reconstruction. The long-term signal is represented as a 30-year loess filter of the NDJF seasonal mean for observations (dark red; the dashed line includes data to the 2019/20 season, the solid line includes data to 2015/16 season) and LDsss prediction (black). The observed 1960−1990 mean +2σ and predicted 1850-1900 mean +2σ are shown. Note the 1960-1990 FFDI mean (7.13) is equal between the observations and prediction. Red hexagons = notable fire activity reported within or near the reconstruction region (area burned >0.5 M ha and/or properties/lives lost - 1926/27; 1938/39; 1957/58; 1964/65; 1968/69; 1979/80; 1982/83; 1993/94; 1997/98; 2001/02; 2002/03; 2006/07; 2012/13; 2013/14) (see Methods). b Number of 11-year moving periods with November to February seasonal FFDI observations and prediction > 1960–1990 mean (7.13). c Schematic of surface synoptic-scale weather systems (black solid arrows represent wind direction, red lines indicate the location of high-pressure systems, blue lines indicate low pressure/cold fronts) and stratospheric Antarctic polar vortex conditions (strength indicated by width of dashed arrows) over November to February that support the connection between above average fire weather hazard in eastern Australia and decreased Law Dome summer sea-salt aerosol concentration in the East Antarctic ice core. d As for c, favourable conditions for supporting the connection between below-average fire weather hazard in eastern Australia and increased Law Dome summer sea-salt aerosol concentration. Location of Law Dome marked with black dot.
