Simulating Meteorological Conditions in Forest Gaps using a Coupled Fire-Atmosphere Model

Simulations from a numerical weather prediction model with a 1-way fire parameterization have established that gaps in an otherwise homogeneous forest can modulate meteorological conditions in the vicinity of a surface-based, low-intensity wildland fire. These simulations have shown that forest gaps affect the vertical and horizontal transport of heat away from the fire and produce heterogeneities in sub-canopy wind and turbulence. It is hypothesized that the influence of forest gaps on heat, wind, and turbulence characteristics can affect the potential for a sub-canopy fire to damage the forest overstory, even during low-intensity wildland fires.

Vertical and horizontal heat transport and horizontal heterogeneities in wind and overstory conditions can alter fire characteristics across a range of spatial and temporal scales. To investigate the effect of heat, wind, and overstory on a fire, a 2-way interactive fire-atmosphere model is used to simulate conditions in forest gaps at temporal and spatial scales consistent with fire-induced temperature and vapor pressure deficit variations that are known to cause tree damage. This study employs the Wildland-Urban Interface Fire Dynamics Simulator (WFDS) model to produce a series of idealized simulations of fire and meteorological conditions consistent with a low-intensity surface fire beneath a forest overstory. Sensitivity studies using the WFDS simulations demonstrate the potential for gaps in the overstory to contribute to the production of temperature and vapor pressure deficit perturbations that can cause tree damage during a surface-based, low-intensity wildland fire.