Chapter 6 Airborne Remote Sensing of Wildland Fires [chapter]

Philip J. Riggan, Robert G. Tissell
2008 Developments in Environmental Science  
In wildland fire management, reliable fire intelligence is needed to direct suppression resources, maintain firefighter safety, predict fire behavior, mitigate fire effects in the environment, and justify and evaluate the effectiveness of fuel management. Fire intelligence needs to be synoptic, quantitative, consistent, and timely. Airborne remote sensing with specialized infrared radiometers is now providing an unprecedented level of information on fire behavior and effects. The temperature,
more » ... diant intensity, carbon and sensible heat fluxes, and fuel consumption associated with the flaming front of a wildland fire have been estimated by remotely measuring its radiance at short-and mid-wave infrared wavelengths. Measurements of upwelling longwave or thermal-infrared radiation provide estimates primarily of ground-surface temperatures, even beneath flaming fronts, that reflect a local time course of energy release and fuel consumption. Characteristics of flames and hot ground can be discriminated from radiances measured at wavelengths near 1.6, 3.9, and 11.9 mm. Fire radiance at 3.9 mm appears to be a good estimator of radiant-flux density, which integrates across wavelengths. There are strong temperature gradients along and within flaming fronts, and although their temperatures are high-commonly exceeding 10001C along the line of a savanna fire, for instance-flames may not be bright when compared with a blackbody radiator. The combination of that low bulk emissivity and uncertainty as to the composition and radiance of nonfire background within the sensor's instantaneous field of view dictates that fire properties are best estimated from measurements of high spatial resolution in comparison with the scale of a fire front. The USDA Forest Service is now applying a FireMappert thermalimaging radiometer for fire research and support of incident command teams over high-priority wildland fires, especially those threatening cities and communities in southern California. Resulting data are providing insight into fire behavior in complex and changing fuels, fire interactions with the atmosphere and a changing climate, and large-scale fire processes. Introduction Large wildland fires burning under high winds in highly flammable fuels and with high values at risk-such as during the October 2007 fire emergency in southern California-demand sophisticated monitoring and communication of fire activity and spread. For tactical firefighting in such situations, reliable fire intelligence and an ability to understand and predict fire behavior are needed to effectively deploy resources-engines, personnel, and aircraft; to keep firefighters safe; and to tailor the allocation of resources to the fire, reducing the need to commit more resources than necessary and reducing costs of suppression. After the emergency, data on fire severity are needed to mitigate fire effects in the environment. On a strategic level, an ability to accurately predict fire behavior is requisite to design, justify, and evaluate approaches for fire management, including landscape-scale fuel treatments. Modern remote sensing can supply the intelligence needed for fire management and the data required for understanding and modeling fire behavior and effects in the environment. Frequent, high-resolution remote sensing at infrared wavelengths can track fire-line rate of spread and acceleration, the location and rates of spotting ahead of a fire front, and structure ignition in residential communities. Together with global positioning system (GPS)-based asset tracking, remote sensing could improve firefighter safety by showing incident commanders the spatial relation of firefighters and equipment to the fire, and especially to regions of high fire intensity or activity. High-resolution imaging also has the potential to accurately quantify large-fire energy release or intensity, residence time, fuel consumption rate, carbon emissions, and soil heating Riggan et al., 2004) . The challenge is to deduce meaningful and useful fire properties based on measurements of upwelling infrared radiation, which will penetrate smoke, with some attenuation depending on wavelength, but not condensed-water clouds. At present in the United States, national airborne infrared mapping operations collect fire imagery at night with fire-perimeter maps made available for early morning briefings of the incident-management team.
doi:10.1016/s1474-8177(08)00006-5 fatcat:bm5dk2rt5nazloxhbm6qvnnnmi