Composite Wildfire Impact (CWI) rating: Integrating fire intensity and burn severity earth observations

Current wildfire impact assessments at the landscape scale often overlook the complexity of active fire behaviour, focusing only on pre- and post-fire spectral differencing, despite remotely sensed active fire data being readily available. This study integrates high temporal resolution active fire intensity measures from geostationary satellite sensors and high spatial resolution normalised spectral differencing index products from polar-orbiting satellite sensors to produce a new approach for describing wildfire impact. Himawari-8 BRIGHT/AHI Fire Radiative Power (FRP) estimates are combined with Normalised Burn Ratio (NBR) metrics from Sentinel-2, to derive wildfire impact categories over Australia for one year of data, using a clustering approach. The wildfire impact categories summarise fire hotspot commonalities based on their maximum and total FRP, duration, differenced NBR (dNBR), burned area patchiness, and pre-fire NBR, and reveal expected 2019-2020 Australian fire season patterns. Furthermore, land cover emerges as an important factor, with forests and woodlands reflecting higher impact fires compared to grasslands and shrublands. Our wildfire impact categories show a moderate agreement with burn severity assessments conducted by state governments, further stressing the need for more diverse information inclusion in such assessments. The proposed composite wildfire impact rating combines diverse remotely sensed wildfire behaviour information and can assist in a better understanding of wildfire effects on a continental scale. More research, leveraging longer temporal and spatial baselines and fire ecology expertise, is needed to refine the used nomenclature for the improvement of wildfire impact assessments. • Geostationary earth observations contain important fire behaviour information • Fire intensity and burn severity are combined into a new wildfire impact metric • CWI ratings are higher in forests and woodlands than in grasslands • CWI ratings reveal familiar patterns of the 2019-2020 fire season across Australia • CWI enables a comprehensive fire characterisation using earth observations