Tracking a Rangeland Fire With Infrasound Arrays

Abstract We present the first infrasound analyses of a rangeland fire and demonstrate infrasound's potential in monitoring wildland fires. We recorded a prescribed fire in sagebrush steppe in cool, moist conditions, using eight infrasound arrays of diverse size (3–44 sensors, 10–200 m width) and distance (0–20 km), including four arrays inside the burn area. Infrasound arrays within 2 km of fires detected coherent infrasound between 1 and 10 Hz, both during active ignitions and also while existing fires continued burning during breaks in ignitions. During periods of active ignitions, the direction of arrival estimated by a 44‐sensor array closely tracked the actual locations where the helicopter was igniting vegetation. Despite being farther from the fire than four smaller arrays, the 44‐sensor array performed best at identifying coherent infrasound and yielding consistent directions of arrival. Our results show infrasound's potential for tracking low‐intensity wildland fires in research or hazard monitoring.