First observations of turbulence generated by grass fires

Abstract

Wildland fires radically modify the atmospheric boundary layer by inducing strong fire‐atmosphere interactions. These interactions lead to intense turbulence production in and around the fire front. Two field experiments were conducted in tall‐grass fuels to quantify turbulence generation during the passage of wind‐driven fire fronts. Observations showed that the measured turbulence generated by the fires was five times greater than the turbulence in the ambient environment. The production of the turbulence at the surface near the fire front was caused by increased variance of the ambient wind, while the buoyancy was strongest at higher levels within the fire plume. Immediately after the fire front passage, turbulence kinetic energy decreased to ambient levels and was associated with strong downdrafts that occurred behind the fire front.