Observations of atmospheric canopy layer turbulence generated by a low-Intensity prescribed fire

Low-intensity prescribed fires (LIPF) can be a viable tool for managing forest ecosystems. However, LIPF may radically modify the atmospheric environment within canopy layers by inducing strong fire-atmosphere interactions. These interactions can lead to intense turbulence production in and around the fire front. As part of a broad Joint Fire Science Program project to develop modeling tools for predicting smoke dispersion from low-intensity fires, the USDA Forest Service - Northern Researth Station conducted a LIPF on a forested plot in the New Jersey Pine Barrens to collect meteorological and air-quality data that can be used for model validation. Included in the suite of meteorological observations during the LIPF are high-frequency (10 Hz) wind data for assessing the ambient and fire-induced atmospheric turbulence regimes within and in the vicinity of the LIPF. This study is focused on an assessment of the production and dissipation of turbulent kinetic energy (TKE) at and in the vicinity of the fire front during the LIPF experiment. Observations showed that the measured turbulence generated by the LIPF was much greater than the turbulence in the ambient atmospheric canopy layer (ACL) environment. The production of turbulence at the surface near the fire front was associated with increased variance in the three-dimesional (3D) winds, specially in vertical direction, while buoyancy was strongest at higher levels within the fire plume. Immediately after the fire front passage,TKE decreased to ambient ACL levels and was associated with strong downdrafts that occurred behind the fire front.