The Fire and Smoke Model Evaluation Experiment (FASMEE) is designed to collect integrated observations from large wildland fires and provide evaluation datasets for new models and operational systems. Wildland fire, smoke dispersion, and atmospheric chemistry models have become more sophisticated, and next-generation operational models will require evaluation datasets that are coordinated and comprehensive for their evaluation and advancement. Integrated measurements are required, including ground-based observations of fuels and fire behavior, estimates of fire-emitted heat and emissions fluxes, and observations of near-source micrometeorology, plume properties, smoke dispersion, and atmospheric chemistry. To address these requirements the FASMEE campaign design includes a study plan to guide the suite of required measurements in forested sites representative of many prescribed burning programs in the southeastern United States and increasingly common high-intensity fires in the western United States. Here we provide an overview of the proposed experiment and recommendations for key measurements. The FASMEE study provides a template for additional large-scale experimental campaigns to advance fire science and operational fire and smoke models.
The distribution of fuels is recognised as a key driver of wildland fire behaviour. However, our understanding of how fuel density heterogeneity affects fire behaviour is limited because of the challenges associated with experiments that isolate fuel heterogeneity from other factors. Advances in fire behaviour modelling and computational resources provide a means to explore fire behaviour responses to fuel heterogeneity. Using an ensemble approach to simulate fire behaviour in a coupled fire–atmosphere model, we systematically tested how fuel density fidelity and heterogeneity shape effective wind characteristics that ultimately affect fire behaviour. Results showed that with increased fuel density fidelity and heterogeneity, fire spread and area burned decreased owing to a combination of fuel discontinuities and increased fine-scale turbulent wind structures that blocked forward fire spread. However, at large characteristic length scales of spatial fuel density, the fire spread and area burned increased because local fuel discontinuity decreased, and wind entrainment into the forest canopy maintained near-surface wind speeds that drove forward fire spread. These results demonstrate the importance of incorporating high-resolution fuel fidelity and heterogeneity information to capture effective wind conditions that improve fire behaviour forecasts.
17The 'Spring Dip' in conifer live foliar moisture content (LFMC) has been well documented but 18 the actual drivers of these variations have not been fully investigated. Here we span this 19 knowledge gap by measuring LFMC, foliar chemistry, foliar density and foliar flammability on 20 new and old foliage for an entire year from both Pinus resinosa (red pine) and Pinus banksiana 21 (jack pine) at a site in Central Wisconsin. We found that needle dry mass increased by up to 70% 22 in just three weeks and these increases were manifested as strong seasonal variations in foliar 23 moisture content and foliar density. These needle dry mass changes were driven by an 24 accumulation of starch in old foliage, likely resulting from springtime photosynthesis onset, and 25 also by accumulations of sugar and crude fat in new needles as they fully matured. Foliar starch, 26 sugar and crude fat content accounted for 84% of the variation in foliar density across both 27 species. Flammability differences were also strongly related to changes in foliar density, where 28 density accounted for 39% and 25% of the variations in foliar time-to-ignition of jack pine and 29 red pine respectively. Finally, we use the computational fluid dynamics-based wildland fire 30 model FIRETEC to examine how these foliar physio-chemical changes may influence wildland 31 fire behavior. Under the lowest canopy density and windspeed, simulated fires in dormant 32 condition stands did not propagate as crown fires while spring dip stands successfully spread as 33 crown fires as a result of the higher potential energy content of the canopy. Simulated wildland 34 fire spread rates increased by as much as 63%, nominal fireline width increased by as much as 35 89% and active fire area more than doubled relative to dormant season fuel conditions and the 36 most significant changes occurred in areas with low canopy cover and low within-tree bulk 37 density. Our results challenge the assumption that live conifer foliage flammability is limited 38 only by its water content; this study suggests a new theory and an expanded view of the factors 39 that dominate live fuel flammability and that subsequently influence larger scale wildland fire 40 behavior. 41 44 4 1. Introduction 53 54 Jack pine (Pinus banksiana) and red pine (Pinus resinosa) are distributed throughout much of the 55 high latitude and temperate North American forests; collectively they cover parts of eleven US 56 states and eight Canadian provinces. Wildfires are an integral component of their ecology 57 (Ahlgren and Ahlgren , 1960). Fires that occur in these areas can vary from low intensity surface 58 fire to high intensity crown fires. Fire severity significantly affects the ecological succession and 59 subsequent distribution of these trees throughout the boreal region (Arseneault, 2001). It is 60 therefore important to develop a complete understanding of the factors that drive fire severity in 61 these forests. 62Fire behavior in these forests is a crucial component of the development of manage...
A navegação consulta e descarregamento dos títulos inseridos nas Bibliotecas Digitais UC Digitalis, UC Pombalina e UC Impactum, pressupõem a aceitação plena e sem reservas dos Termos e Condições de Uso destas Bibliotecas Digitais, disponíveis em https://digitalis.uc.pt/pt-pt/termos.Conforme exposto nos referidos Termos e Condições de Uso, o descarregamento de títulos de acesso restrito requer uma licença válida de autorização devendo o utilizador aceder ao(s) documento(s) a partir de um endereço de IP da instituição detentora da supramencionada licença.Ao utilizador é apenas permitido o descarregamento para uso pessoal, pelo que o emprego do(s) título(s) descarregado(s) para outro fim, designadamente comercial, carece de autorização do respetivo autor ou editor da obra. Na medida em que todas as obras da UC Digitalis se encontram protegidas pelo Código do Direito de Autor e Direitos Conexos e demais legislação aplicável, toda a cópia, parcial ou total, deste documento, nos casos em que é legalmente admitida, deverá conter ou fazer-se acompanhar por este aviso.Fire effects on the physical environment in the WUI using FIRETEC Autor(es):Pimont, F.; Dupuy, J-L.; Linn, R. R. AbstractIn France, the clearing distance between buildings and forest edge is 50 m, to allow fire fighters to protect those buildings. Current building recommendations in the wildland-urban interface derive from fire-safety tests on building materials using heat exposures (duration and magnitude) that are expected to be different from those produced by wildfires. Beyond a few experimental data released after the International Crown Fire Modelling Experiment, there is a lack of characterisation of the physical environment of a building or human target within a cleared area, that receives hot gases and radiant fluxes from a crown fire. In the present study, we evaluate FIRETEC's ability to simulate heat fluxes based on some available experimental data and subsequently use it to characterize the radiant fluxes, gas temperatures and velocities around a human or building target.Simulations have been performed in a mature Aleppo pine forest within a 600 by 400 m domain. The conditions of the fire spread were severe (30°C, wind up to 50 km/h, slope until 30%). Radiant fluxes and gas temperatures were computed for several distances between the forest tailing edge and a target that represents either a building or a fire fighter. Peak radiant heat flux magnitudes decreased by about 80% when the target was at 50 m compared to a target at 10 m. This is between 90 and 95% reduction o0f radiant flux reduction observed at 50 m compared to the forest edge. For the purpose of comparison with reference acceptable thresholds for both materials and fire fighters, the peak values of the average over one minute of the instantaneous radiant fluxes and gas temperatures were computed. These values support the notion that a clearing distance of 50 m is appropriate in the tested conditions for both thermal radiation and gas temperature, even if radiant fluxes remain high ...
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