Meteorological drivers of the eastern Victorian Black Summer (2019–2020) fires
Graham Mills
A * , Owen Salkin B , Matthew Fearon C , Sarah Harris D , Timothy Brown C and Hauss Reinbold C
+ Author Affiliations
- Author Affiliations
A School of Earth, Atmosphere and Environment, Monash University, Clayton, Vic., Australia.
B Natural Systems Analytics, Noojee, Vic., Australia.
C Division of Atmospheric Sciences, Desert Research Institute, Reno, NV, USA.
D Fire and Emergency Management, Country Fire Authority, East Burwood, Vic., Australia.
* Correspondence to: gam4582@gmail.com
Journal of Southern Hemisphere Earth Systems Science 72(2) 139-163 https://doi.org/10.1071/ES22011
Submitted: 30 March 2022 Accepted: 30 July 2022 Published: 8 September 2022
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of BoM. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)
Abstract
The spring and summer of 2019–2020 (Black Summer) saw the largest and most significant bushfire outbreak recorded in eastern Australia. In Victoria, the fires ran from mid-November through early autumn. In this paper, we use a high-spatial and temporal resolution 48-year fire weather re-analysis data set (VicClim5) to describe fire weather and vertical wind and stability profiles for five significant high Forest Fire Danger Index (FFDI) fire events and compare these with detailed fire reconstructions. A feature of several of these fires was very active overnight fire spread driven by topographically enhanced low-level jets and low fine fuel moisture content. The FFDI values on these nights were either the highest or near highest on record in the 48-year data set. We describe cases of lightning ignition, prefrontal fire spread and two cases of post-frontal fire spread – one into Mallacoota on the early morning of 31 December 2019 and the other a northward overnight run down the Buffalo Valley on 4–5 January 2020. On two of the days studied there were complex wind changes associated with the inland penetration of low-level south-easterly winds under the influence of locally generated pressure gradients. An elevated hot, dry mixed layer above these shallow layers also played an important role. On one occasion there is some evidence of possible mountain-wave modulation of surface wind flows. These events demonstrate a range of features of the fire weather and climate in eastern Victoria and the utility of VicClim5 in 3-dimensional climatological analyses.
Keywords: Black Summer bushfires, climatology of extremes, cold fronts, eastern Victorian fire weather, elevated mixed layers, low level jets, overnight fire spread, wind changes.
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