Coupled atmosphere/topography effects on fire behavior

Topographic features affect fire behavior in a variety of ways, including changing ambient winds patterns as well as potentially changing how fires interact with local winds. Topographic features have the ability to amplify the fire-induced flow patterns that are typically expected in the absence of topography or induce flow fields that are entirely scenario specific. The effects of homogenous slope on fire behavior is at least qualitatively understood for scenarios with quiescent conditions or light winds parallel to the slope, but there is much less understanding of the phenomena that occur in more complex scenarios. To improve our capability to anticipate wildfire behavior in rugged topography and provide insights for the development of future operational models, a variety of question arise. For example: how does the acceleration of a fire and potential of a steady state fire spread rate depend on the incident wind angle with respect to slope? How might upwind topography influence the heat transfer and ignition to unburned fuel through their affects on such incident angles? What are the dynamics associated with drainage flows or density currents interacting with fires in narrow canyons? In order to explore potential answers to such questions, we use a coupled fire atmosphere model, FIRETEC, to perform simulations in different configurations. These numerical investigations include both the investigations of continuous spread as well as spotting potential. The results of these simulations highlight the nonlinearly coupled effects of topography and winds on fire behavior and suggest the need for experimental or field observations in various topographic setting to test models driven hypothesis.