Observing Global Spatiotemporal Behaviour in Wildfire Dynamics over the Past Three Decades

Abstract:

Wildfires are intrinsic in the Earth System, influencing land-atmospheric processes in biomes worldwide. While studies have shown a global decrease in fire occurrences, many solely evaluated these trends based on a burn area metric. Therefore, this study seeks to examine additional wildfire behaviour metrics such as fire intensity and spread rate, and analyze the predictor variables that influence wildfire behaviours, such as fuel load and fuel moisture. A 37-year climatology (1981-2017) is conducted to examine the monthly and seasonal spatiotemporal trends and extremes in wildfire behaviour metrics and its predictor variables. Fire behaviour is examined by analyzing the fire weather index, which provides a rating of the fire line intensity; and the initial spread index, which represents the ability of a fire to spread immediately after ignition. The predictor variables analyzed are the buildup index that characterizes the total fuel available for a fire; and the three moisture code components that track the moisture content of litter on the forest floor (fine fuel moisture, duff moisture, and drought). These indices and components are based on the Canadian Fire Weather Index System and are calculated from an array of meteorological and ecological parameters estimated from NASA’s Modern Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) product at 0.5° resolution. Preliminary results indicate that fire intensity increased at a greater rate over the Amazon in South America than any other region worldwide. Areas of higher fire intensity and spread rates are spatially correlated with biomes experiencing extreme drought in both compacted and loosely compacted organic matter. This analysis provides essential information on the dynamic controls influencing the changes in wildfire frequency, intensity, and duration for different fire regimes worldwide. These results can help scientists and policymakers gain a greater understanding of the complex biophysical feedbacks of wildfires on the ambient environment, as well as focus efforts on improving adaptation and mitigation strategies, specifically for fire prone regions.