Fire Rate of Spread and Growth Rate in a Set of 30 Global Wildfires: New Evidence of Extreme Fire Behavior

Abstract

Wildfire science needs new methods to evaluate and predict wildfire behavior and impacts. In this study, we present a new algorithm that calculates the maximum fire rate of spread resulting from a fire progression map made of isochrones, according to 1) the shape of the isochrones, and/or 2) prevailing atmospheric wind direction. We have applied the algorithm to a set of 30 fires, differentiated according to the way the isochrone map was surveyed: by firefighters’ GPS positioning (in Europe, ~ 1-hour frequency), or by satellite data (North and South America, and Australia, ~ 12-hour frequency). The rate of spread was also related to the growth rate in hectares, and with the morphology of the fire scar. Our results reveal maximum speeds of 8.62 and 6.79 km/h for the GPS and satellite datasets respectively. In general, the GPS dataset shows faster runs that burn smaller extensions than the satellite dataset. Runs following wind direction are more elongated than the ones driven by other factors, which show more expansive runs. The algorithm presented here can be useful for the study of the factors influencing fire propagation.

Keywords: algorithm, burnt area, extreme wildfire events, fire progression, rate of spread, remote sensing, wildfire