Modeling wildland fires : A description of the Coupled Atmosphere-Wildland Fire Environment model (CAWFE) by Janice L. Coen

2013-02-04

Technical Report

This work describes the Coupled Atmosphere Wildland Fire Environment (CAWFE) model, which is used to simulate wildland fires. CAWFE is comprised of a numerical weather prediction model and a fire behavior module, two-way coupled such that atmospheric conditions, along with fuel properties and terrain slope, determine how fast and in what direction a fire spreads. The heat released by the fire in turn affects the wind in its vicinity, notably producing fire winds. The atmospheric model is a nonhydrostatic numerical weather prediction model designed to work at high resolutions (hundreds of meters) in complex terrain. At the surface, each atmospheric grid cell is further divided into two-dimensional fuel cells. The fire module represents a surface fire and a crown fire traveling through tree canopies. It is comprised of a tracer method for defining and tracking a subgrid-scale interface and a combination of empirical, semi-empirical, and other methods for representing processes such as the rate of spread of the flaming front, post-frontal heat release, calculation of sensible and latent heat fluxes released by the fire, crown fire ignition and heat release, smoke production, and the upscaling and reintroduction of heat fluxes into the atmospheric model. We describe the input data and experiment design, and describe the model output and visualization of the atmospheric dynamics, fire behavior, and smoke.