Fire Behavior
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We examined the hourly diurnal cycle of 23,557 fires and identified 1,095 overnight burning events (OBEs, each defined as a night when a fire burned through the night) in North America during 2017–2020 using geostationary satellite data and terrestrial fire records. A total of 99% of OBEs were associated with large fires (>1,000 ha) and at least one OBE was identified in 20% of these large fires. OBEs were early onset after ignition and OBE frequency was positively correlated with fire size. Although warming is weakening the climatological barrier to night-time fires6, we found that the main driver of recent OBEs in large fires was the accumulated fuel dryness and availability (that is, drought conditions), which tended to lead to consecutive OBEs in a single wildfire for several days and even weeks. Critically, we show that daytime drought indicators can predict whether an OBE will occur the following night, which could facilitate early detection and management of night-time fires. We also observed increases in fire weather conditions conducive to OBEs over recent decades, suggesting an accelerated disruption of the diurnal fire cycle.
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Join us in the field to discuss prescription burn planning, treatments, monitoring, and results with Duncan Leao, Steve Howell, and Ali Paulson, USFS. This is an informal discussion open to all.
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Fuel-treatments targeting shrubs and fire-prone exotic annual grasses (EAGs) are increasingly used to mitigate increased wildfire risks in arid and semiarid environments, and understanding their response to natural factors is needed for effective landscape management. Using field-data collected over four years from fuel-break treatments in semiarid sagebrush-steppe, we asked 1) how the outcomes of EAG and sagebrush fuel treatments varied with site biophysical properties, climate, and weather, and 2) how predictions of fire behavior using the Fuel Characteristic Classification System fire model related to land-management objectives of maintaining fire behavior expected of low-load, dry-climate grasslands. Generalized linear mixed effect modeling with build-up model selection was used to determine best-fit models, and marginal effects plots to assess responses for each fuel type. EAG cover decreased as antecedent-fall precipitation increased and increased as antecedent-spring temperatures and surface soil clay contents increased. Herbicides targeting EAGs were less effective where pre-treatment EAG cover was >40 % and antecedent spring temperatures were >9.5 °C. Sagebrush cover was inversely related to soil clay content, especially where clay contents were >17 %. Predicted fire behavior exceeded management objectives under 1) average fire weather conditions when EAG or sagebrush cover was >50 % or >26 %, respectively, or 2) extreme fire weather conditions when EAG or sagebrush cover was >10 % or >8 %, respectively. Consideration of the strong effects of natural variability in site properties and antecedent weather can help in justifying, planning and implementing fuel-treatments.
In 2024, there were five Thursdays in February. To celebrate this rare event, the Fire Lab is hosting a series of five seminars that highlight new tools and research for managers. The “February Five” will occur during our regularly scheduled seminar series timeslot – Thursdays at 11am Mountain Time. Please join us on Teams. Select the titles below for connection information and to view recordings after the event.
FastFuels and QUIC-Fire: 3D fuel and fire modeling systems supporting prescribed fire
Feb 1, 2024: Russell Parsons, Research Ecologist
The Fire Weather Alert System
Feb 8, 2024: Jason Forthofer, Research Mechanical Engineer; Natalie Wagenbrenner, Research Meteorologist
Estimating forest characteristics such as carbon and tree growth over space and time using TreeMap, FIADB, and FVS
Feb 15, 2024: Karin Riley, Research Ecologist and John Shaw, Forest Inventory and Analysis
Behave7 Fire Modeling System: A Long Time Coming
Feb 22, 2024: Faith Ann Heinsch, Physical Scientist; LaWen Hollingsworth, Fire Behavior Specialist; Greg Dillon, Director, Fire Modeling Institute
Wildfire risk and mitigation opportunities in the US sagebrush biome
Feb 29, 2024: Karen Short, Research Ecologist
Webinar recording.
The complex interactions between atmospheric and fire-induced winds are a persistent obstacle to accurately predicting wildfire front behavior. There are a multitude of wildfire spread models, with one primary distinction being the level of fire-atmosphere coupling in each. Coupling of fire-induced winds and ambient winds in numerical models is carried out through linking the heat and mass fluxes from the wildfire with the surface energy fluxes in the atmospheric model. The challenge in this coupling is increased with the introduction of heterogenous surface conditions, e.g., terrain, canopies, buildings. To better understand the dynamic coupling of fire-induced winds and atmospheric winds at microscales, the fast-response wildfire model QES-Fire was used to study the effects of fire-induced winds near structures, and the relative importance of the momentum deficits caused by canopies and structures on fire-induced winds.
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While prescribed fire and mechanical treatments in shrublands experiencing tree expansion restored understory vegetation and prevented continued juniper and pinyon infilling and growth, these fuel treatments also increased modeled surface fire behavior. Thus, management tradeoffs occur between desired future vegetation and wildfire risk after fuel treatments.
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The story of how fire managers slowed a fire and benefited the ecosystem. This was accomplished thanks to previous fires that were managed for resource benefit. This is the story of the 2021 Rafael Fire that started just 20 miles outside of Flagstaff, AZ. On day 2 the fire ran 12 miles towards town, causing evacuations and worry. Things changed on day 3, watch the video to learn more. This video contains beautiful drone footage of unhealthy forests and the benefits of fire. Thanks to a shift in fire management, a bad situation was transformed into a beneficial one.
Webinar recording.
Fires of Unusual Size (FOUS) are large fires that exhibit at least one rapid growth event, and keep growing after that. While “megafire” is widely used and has no specific definition, FOUS are defined by specific characteristics. We can count how many happen each year, and we can ask scientific questions about how they differ from other fires. What makes them so big? What triggered the big growth event(s)? Are they increasing each year? Brian Potter, Research Meteorologist with the Pacific Northwest Research Station, will talk about the trends, look at how weather influences their growth, and give some examples of unanswered questions about them.
Webinar recording.
In an effort to address key capability gaps, the NOAA National Environmental Satellite, Data, and Information Service (NESDIS) has established a Wildland Fire Program focused on impactful service delivery. NESDIS Wildland Fire Program projects, aimed at addressing critical active fire capability gaps, are underway, with product and service demonstrations expected to begin by July 2023. The improved products are generated using the Next Generation Fire System (NGFS), which consists of a sensor agnostic (applicable to geostationary or low earth orbit satellites) active fire algorithm and higher order capabilities, including alerting, incident situational awareness tools that are highly tolerant of cloud cover, and an event-based data model that combines time-resolved satellite fire detections with complementary geospatial data layers. Terrain corrected GOES-R ABI imagery and fire detections have also been developed. In addition, a lightning prediction model, customized for incident management, is under development. With Alaska wildland fire applications in mind, this presentation will introduce the NESDIS Wildland Fire Program, highlight product development and demonstration activities, and facilitate continued dialogue with stakeholders.