Collection and analysis of infrared observations of fire-atmosphere dynamics

Observations of the dynamics of wildfires are limited, particulary at the fine scales at which fireline vortex dynamics occurs. To address this problem, we have developed a technique that uses infrared videocamera imagery, either mounted on the ground or on an airplane, to investigate the fine-scale dynamics within firelines. This work reviews the observations and analysis of data collected from a tower during the burn of Plot 6 during ICFME (International Crown Fire Modeling Experiment) in 1997, from the National Science Foundation's C130 aircraft during WiFE (WildFire Experiment) in 1998, and from a cherry picker near Australian grass fires in 1998. In these experiments, infrared imagery was collected with an Inframetrics Thermacam and analyzed using image flow analysis to estimate of air velocities and follow features within the fireline. In ICFME, the analysis revealed 10-30 m/s updrafts, 10-20 m/s downdrafts, 5-10 m/s horizontal winds, and pairs of counterrotating towers within the fireline. WiFE demonstrated that these observational and analysis techniques could be used on airplanes, with corrections in analysis for the aircraft motion. One particular flight sequence near Glacier National Park captured a finger of flame shooting approximately 60 m ahead of a fireline over a few seconds. Data from the grass burns in Australia are still being analyzed, but preliminary results show the observed dynamics of the crown fire and the intense grass fires near Darwin are highly similar.