Multi-scale analyses of wildland fire combustion processes: Small-scale field experiments – three-dimensional wind and temperature

The United States Department of Defense (DoD) Strategic Environmental Research and Development Program (SERDP) funded project: "Multi-scale Analyses of Wildland Fire Combustion Processes in Open-canopied Forests using Coupled and Iteratively Informed Laboratory-, Field-, and Model-based Approaches (RC-2641)" small-scale field experiments were designed to investigate how contrasting fuel conditions (e.g., fuel load, particle type, bulk density), fire spread type (e.g., heading vs. backing), and ambient conditions (e.g., seasonality, moisture, flow, air and fuel temperature) influenced physical processes associated with combustion (e.g., heat transfer, flame propagation, flow) and the scale-dependent coupling of these processes. Additionally, these experiments provide 1) a linkage between small-scale laboratory combustion experiments and large-scale operational prescribed fires, and 2) archived datasets for further model development and evaluation. Our experimental design incorporates complementary approaches, methods, and instrumentation employed at these other scales, to quantify critical properties of the experimental fires’ physics domains (e.g., fuels and ambient conditions) and processes associated with combustion (e.g., heat transfer, flame propagation, flow). The small-scale field experiments include a series of highly instrumented, intermediate-scale experiments conducted on 100 square meter plots at the Silas Little Experimental Forest, New Lisbon, New Jersey. This dataset contains data collected from thirty-four burns in 2018 and 2019 from sixteen sonic anemometers (81000v, R.M. Young Inc.) which were mounted on aluminum trusses at 2.5 to 3.0 meter (m) heights (depending on the specific experiment) in a 4 by 4 grid over fuel beds for all experiments except two (burns 7 and 8 conducted in May 2018), when sonics were mounted only on trusses B and C at two heights (1.5 m and 3.5 m). A single sonic was mounted on the plot center tower (CT) approximately 8 m above the ground for all burns. Sonic anemometers were logged at 10 hertz (Hz) using four CR3000 dataloggers (Campbell Scientific). In addition, a single sonic anemometer (81000v, R.M. Young Inc.) was added as a control tower, starting with burn 4. The sonic anemometer was mounted at 3m, directly above a pressure sensor, and were logged at 10 Hz on a single CR1000 datalogger (Campbell Scientific). The control tower was located approximately 50 m south of burn area. The sonic anemometer data were used to explore fine-scale patterns of vertical turbulence above flame fronts. Pre-fire data were used to quantify ambient wind conditions before and after fire front passage, turbulence, sensible (convective) heat fluxes, and momentum fluxes above flame fronts during fires. Data include sampled horizontal and vertical wind speed (meters per second (m/s)) and temperature (degrees Celsius (°C)).
Many DoD facilities utilize low intensity prescribed fire to manage hazardous fuels, restore ecological function and historic fire regimes, and encourage the recovery of threatened and endangered species in the forests they manage. Current predictive models used to simulate fire behavior during low-intensity prescribed fires (and wildfires) are empirically based, simplistic, and fail to adequately predict fire outcomes because they do not account for variability in fuel characteristics and interactions with important meteorological variables. This study used a suite of measurements at the fuel particle, fuel bed, field plot, and stand scales to quantify how variability in fuel characteristics and key meteorological factors interact to drive fire behavior during low intensity prescribed burns. These experiments were designed to inform the development and evaluation of physics-based models that explicitly account for combustion, turbulent transfer, and energy exchange by coupling and scaling individual component processes. These datasets provide measurements to improve the understanding of, and ability to accurately predict, fire behavior under a wide range of management scenarios.
A summary of the SERDP Project RC-2641 can be found at the RC-2641 Project Overview (serdp-estcp.org): https://www.serdp-estcp.org/Program-Areas/Resource-Conservation-and-Resiliency/Air-Quality/Fire-Emissions/RC-2641. Please reference the plot layout and documentation data publication (Gallagher et al. 2022) as these data provide the sensor locations of each burn, a detailed description of data collected and a burn summary.