Variability, trends, and drivers of regional fluctuations in Australian fire activity

Abstract

Throughout the world fire regimes are determined by climate, vegetation, and anthropogenic factors, and they have great spatial and temporal variability. The availability of high‐quality satellite data has revolutionized fire monitoring, allowing for a more consistent and comprehensive evaluation of temporal and spatial patterns. Here we utilize a satellite based “active fire” (AF) product to statistically analyze 2001–2015 variability and trends in Australian fire activity and link this to precipitation and large‐scale atmospheric structures (namely, the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD)) known to have potential for predicting fire activity in different regions. It is found that Australian fire activity is decreasing (during summer (December–February)) or stable, with high temporal and spatial variability. Eastern New South Wales (NSW) has the strongest decreasing trend (to the 1% confidence level), especially during the winter (JJA) season. Other significantly decreasing areas are Victoria/NSW, Tasmania, and South‐east Queensland. These decreasing fire regions are relatively highly populated, so we suggest that the declining trends are due to improved fire management, reducing the size and duration of bush fires. Almost half of all Australian AFs occur during spring (September–November). We show that there is considerable potential throughout Australia for a skillful forecast for future season fire activity based on current and previous precipitation activity, ENSO phase, and to a lesser degree, the IOD phase. This is highly variable, depending on location, e.g., the IOD phase is for more indicative of fire activity in southwest Western Australia than for Queensland.

Changes in Fire Activity in Africa from 2002 to 2016 and Their Potential Drivers

“…Recent trends in terrestrial moisture may be the result of internal climate variability including El Niño–Southern Oscillation (ENSO) and sea surface temperatures in the tropical Pacific and Indian Oceans (Andela & van der Werf, ; Earl & Simmonds, ; Rocha & Simmonds, , ). However, looking at the regional scale, Hulme et al () established strong forcing of ENSO only in southeastern and eastern equatorial Africa, while Western Africa region with the strongest decline in BA showed little or no rainfall sensitivity to ENSO.…”

Spatial and Temporal Variability and Trends in 2001–2016 Global Fire Activity

“…Studies utilizing different fire level measures can arrive at different conclusions when investigating fire variability and trends (e.g., Doerr & Santín, 2016;Hantson et al, 2013;North et al, 2015;San-Miguel-Ayanz et al, 2013). BA and AF products are most commonly used for measuring fire levels of a region, and they have both advantages and disadvantages (see Earl & Simmonds, 2017). BA products are, by their nature, less sensitive to changes in smoke and cloud cover as they draw upon multiple satellite Journal of Geophysical Research: Atmospheres 10.1002/2017JD027749 overpasses, collecting data after the fire event, whereas the AF daily product is based on passes from individual days (Randerson et al, 2012).…”

“…As part of the Collection 6 land product reprocessing (commenced in May 2015), advancements have been made to the fire detection algorithm and swath-level product, which has reduced some of the limitations of Collection 5, including fires obscured by smoke (Giglio et al, 2016) and false alarms from solar reflection (see He & Li, 2011). Collection 6 MOD14A1 data can still be disrupted by cloud cover, blocking the satellites line of sight, however, Earl and Simmonds (2017) demonstrate that there was no significant impact when correlated with high-quality CALIPSO cloud fraction data. There are other AF products available, for example, from Geostationary Operational Environmental Satellites WF-ABBA (Koltunov et al, 2012), Advanced Very High Resolution Radiometer-based products (see He & Li, 2012;Li et al, 2001), Suomi National Polar-Orbiting Partnership (Hillger et al, 2013), and AF products from the European Space Agency/European Space Research Institute (Arino & Mellinotte, 1998).…”

“…Fires are caused both naturally (mostly by lightning) and anthropogenically (through “prescribed” burning of forests and savannahs for land clearing/management for agricultural and domestic uses). Throughout the world, fire regimes are controlled by climate and vegetation, with precipitation suppressing immediate fire levels, however, encouraging future fires through fuel buildup (Marlon et al, ; Earl & Simmonds, ). Precipitation patterns are strongly influenced by large‐scale atmospheric structures and processes, such as the Intertropical Convergence Zone, the subtropical ridges, the El Niño–Southern Oscillation (Nicholls, ), and the Indian Ocean Dipole (Cai et al, ).…”

“…We stress that many of these studies do not take the important step of conducting statistical tests on diagnosed trends, so it is open to question whether identified trends are above the noise level. In our study we are at pains to conduct such tests, as did Earl and Simmonds (2017) and Andela et al (2017), and point to the importance of ascertaining statistical significance before discussing and interpreting the results. In Australia, fire level trend studies have much discrepancy (see Earl & Simmonds, 2017).…”