The impact of atmospheric boundary layer flow on wildfire behavior

A coupled wildfire-atmosphere LES (Large Eddy Simulation), gives us the ability to examine the sensitivity and impact that different wildfire-atmosphere interactions have on wildfire behavior. Coupled wildfire-atmosphere LES has been slowly gaining legitimacy over the past 20 years, in both the wildfire science and atmospheric science communities, as a valuable tool with which to investigate the importance of the ABL on wildfire, and here, using this modeling approach, we demonstrate the effects of different atmospheric boundary layer (ABL) wind fields on wildfire propagation. Time permitting, we propose to discuss three LES ABL-wildfire scenarios.

In the first scenario, we examine the impact of a turbulent, convectively-driven ABL flow on fire spread.

In the second, we examine the impact of the same turbulent ABL flow on fire brand transport.

In the third, we examine the impact on fire propagation of vertical wind shear in a non-turbulent ABL flow field.

The study will show that, for each scenario, the fire behavior and propagation are sensitive and responsive to ABL winds, and interaction or coupling between ABL flow and the fire plume is critical to how the wildfire behaves and spreads.

Each scenario illustrates: the importance of a coupled wildfire-atmosphere LES to accurate wildfire forecasting; the necessity of an accurate ABL wind forecast for coupled wildfire-atmosphere interactions; the importance of upper-level ABL flow, as opposed to surface flow alone, to the accuracy and uncertainty of any wildfire spread forecast; the fact that no wildfire forecast is deterministic, and that an operational fire-spread and fire-behavior forecast must contain a range of predictions assessed from a statistical or probabilistic point of view.