The Atmospheric Response to Heat Release from a Wildland Fire

Wildland fires directly affect the overlying atmosphere through the release of heat and moisture during the combustion of available fuel. Air perturbed by fire-induced processes interacts with the background atmosphere, producing secondary perturbations via a combination of fluid processes. These secondary perturbations can then feedback on the fire to affect ongoing fire activity across a range of spatial and temporal scales. Investigations into fire-atmosphere interactions can be undertaken via the analysis of field measurements and through the use of coupled fire-atmosphere numerical models. Given the inherent difficulty in collecting field measurements during complex and often dangerous wildland fire events, considerable research has been undertaken to develop and test coupled fire-atmosphere models for the purpose of investigating relevant physical processes, with the ultimate goal of implementing the models operationally into real-time fire management decisions.

This presentation first addresses how research undertaken between Daniel Keyser, University at Albany and Joseph Charney, USDA Forest Service, Northern Research Station helped inform our understanding of how fire-induced perturbations contribute to atmospheric responses that can feedback on fire activity. Historically, it was widely assumed in fire management and fire weather communities that the static stability profile above a wildland fire influences the strength of the updraft above the fire and the horizontal winds in the vicinity of the fire, and that both of these factors affect fire intensity. The research helped establish benchmarks for the atmospheric response to a wildland fire in an idealized two-dimensional numerical model, and informed ongoing investigations into fire parameterizations that account for interactions between the fire and the atmosphere.

Considerable research has followed that was informed by the results of the Charney and Keyser study. Coupled fire-atmosphere simulation experiments were devised and executed to explore the sensitivity of atmospheric responses to simulated fires using a number of existing and newly developed models. This presentation will discuss studies that employ FIRETEC, WFDS, CM1, and ARPS-DEVS and relate the results of those studies to the Charney and Keyser study. The development and implementation of QUIC-Fire, a new model designed specifically for operational application, will also be detailed.