146 Radar Observations of a Prescribed Fire

Thursday, 31 August 2023
Boundary Waters (Hyatt Regency Minneapolis)
Jie Sun, Florida State Univ., Tallahassee, FL; and S. M. Loria-Salazar, K. Speer, M. D. Williams, D. Schvartzman, T. Y. Yu, and M. A. Nelson

Understanding fire and smoke spread is essential to inform the public about exposure and improve mitigation risk strategies as wildfires intensify and fire seasons increase in the U.S. With the above in mind, a DoD prescribed fire was conducted in March 2023 at Eglin AFB and heavily instrumented with in-situ and remote measurement platforms. Here we report on the initial results from Advanced Radar Research Center’s (ARRC) Rapid X-band Polarimetric (RaXPol) radar that sampled the fire plume at high resolution. Data were primarily collected in the range-heigh indicator (RHI) mode, scanning the fire plume through its core for approximately one hour. The large-scale structure of the plume is consistent with a turbulent buoyant plume rising to an equilibrium level some 1.5 km above ground in a moderate background wind.

Horizontal and vertical cross-sections indicate small and larger scale eddy structures associated with entrainment, inflow, and a plume wake in a cross-flow. Vertical sections along the axis of the plume suggest that axial eddies are essential components of the plume development and responsible for the vertical transport of smoke and potential embers near the surface. Horizontal vorticity estimates suggest strong downstream shear at the base of the plume is associated with the growth of these eddies with distance from the base of the plume. Other vorticity patterns at the top of the plume may be consistent with overshoot and buoyant billows near the equilibrium level.

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