Fire Intensity Research Articles

Battle of Kalniškės: a Fragment of the Fight for Freedom

The article analyses the structure and composition of the partisan division – the company of Jonas Neifalta-Lakūnas [‘Pilot’] – that fought in the Battle of Kalniškės and its role within the context of the Lithuanian resistance against the second Soviet occupation. The direct causes of the battle, its progress and individual stages are discussed. The study uses narrative, analytical and inductive approaches. Lakūnas’ company was part of the partisan forces of several rural areas under the leadership of Albinas Kisieliauskas- Karvelis [‘Pigeon’]. Neifalta-Lakūnas, commander of the Kalniškės area partisans, was deputy to Kisieliauskas- Karvelis and the head of the command post. The composition and organisational structure of the force was the same as many other Lithuanian partisan forces. The detachment adopted the structural principles of the independent Lithuanian Army and tailored them to the needs of the guerrilla war. In order to ensure confidentiality, separate smaller groups operated in different areas. These smaller groups were usually made from smaller mobile units formed from men of adjacent villages, and were lead by fighters with experience in the army or police service. From the beginning of the Soviet occupation, this partisan company was trying to unite itself into a centralised resistance movement. Initially a relationship was established with the Lithuanian Freedom Army, and 2 new units – Tauras and Dainava Commands – emerged as a result of this centralisation. The creation of centralised underground structures legitimised the activities of the partisan force. The release of proclamations and regulatory documents by the leadership formed the concept of anti-Soviet resistance, regulated its tactics, discipline and behaviour with the civilian population. However, the chain of subordination was on many occasions disrupted and changed, while orders from command headquarters did not always reach the distant Kalniškės Forest. From February 1945 to March 1945, as far as mobility was concerned, the forces under the leadership of Karvelis and Lakūnas stood out from the rest of the partisan divisions operating in the ethnographic area of Užnemunės Dzūkija [south-western part of Lithuania]. The area of operations of this partisan force, which was extremely mobile and frequently changed its campsite, covered as many as seven rural areas. In the winter of 1944–1945 and spring 1945, up until the famous Kalniškės Battle, these fighters participated in many clashes with the occupational forces, but managed to avoid any major losses. Perhaps one of the most significant of these was the attack on the town of Rudamina and the skirmish at Panara. In both cases the partisans won, believed in the power of their weapons, and did not hesitate to initiate the Battle of Kalniškės. The Battle of Kalniškės was one of many defensive combats fought by partisans in 1945. It started when the NKVD Regiment surrounded the company of Neifalta- Lakūnas camping in the forest. The progress of the battle can be divided into four stages. During the battle partisans could not withdraw in an organised fashion and had to fight the enemy attacks on Meškakalnis hill. Some fighters were cut off from the main division and were scattered to the depths of the forest. After intensive fire, partisan resistance weakened. The NKVD assault group tried to push the partisans from their occupied positions and to completely destroy them, but around 20 men managed to break out of the encirclement. Although the Battle of Kalniškės claimed the lives of nearly 50 partisans, their dedication inspired their brothers in arms, kept the movement smouldering in the nation’s consciousness, and lead to the re-establishment of Lithuania’s independence.

The potential of collaborative solutions to improve management of California (United States) wildlands

Across the western United States and elsewhere, the frequency and intensity of wildland fires are projected to increase, posing a challenge to natural‐resource management. While collaborative, multi‐benefit partnerships can provide opportunities to overcome barriers to effective management, in many cases these collaborations have been slow to form. To investigate this issue, we surveyed natural‐resource professionals in California to identify barriers to effective management and potential solutions in the form of collaborations. Analyzing our data using social network analysis, results show that limited financial and human capital were the most salient barriers in our sample, while lack of public support and data were less common concerns. Collaboration networks were dominated by land‐management and other public agencies, as they were the most frequently mentioned as collaborators. Tribes, universities, private‐sector organizations, and watershed‐service providers mentioned other actors as collaborators more often than they were mentioned as collaborators, while the opposite was true for land‐management and other public agencies. Universities, land managers, watershed‐service providers, and private‐sector organizations displayed a strong desire to establish new collaborations, while other public agencies and tribes displayed less of a desire to do so. Overall, this study highlights insufficient financial and human capital as barriers confronting natural‐resource management in California. It also shows that organizations with the capacity and capability to help mitigate these shortcomings, such as the private sector and universities, are among those most positive toward additional collaborations. Our findings suggest that initiatives to expand regional collaborative partnerships could increase the effectiveness of natural‐resource management in California.

Assessing the Role of Forest Grazing in Reducing Fire Severity: A Mitigation Strategy

This study investigates the role of prescribed grazing as a sustainable fire prevention strategy in Mediterranean ecosystems, with a focus on Sardinia, an area highly susceptible to wildfires. Using FlamMap simulation software, we modeled fire behavior across various grazing and environmental conditions to assess the impact of grazing on fire severity indicators such as flame length, rate of spread, and fireline intensity. Results demonstrate that grazing can reduce fire severity by decreasing combustible biomass, achieving reductions of 25.9% in fire extent in wet years, 60.9% in median years, and 45.8% in dry years. Grazed areas exhibited significantly lower fire intensity, particularly under high canopy cover. These findings support the integration of grazing into fire management policies, highlighting its efficacy as a nature-based solution. However, the study’s scope is limited to small biomass fuels (1-h fuels); future research should extend to larger fuel classes to enhance the generalizability of prescribed grazing as a fire mitigation tool.

Exploring the Interactions of Climate Change, Freshwater Supply, and Environmental Balance

Climate change has far-reaching implications for global freshwater availability and environmental balance. The increase in greenhouse gases from the burning of fossil fuels has triggered global climate change, affecting precipitation patterns, glacier melt and sea level rise. Parts of the United States are experiencing significant changes in precipitation patterns, with some areas experiencing frequent storms and others experiencing more prolonged droughts. Accelerated glacier melt is leading to fewer water sources during the dry season, and sea level rise is threatening coastal freshwater resources, triggering saltwater intrusion and a decline in freshwater quality. Wildfires in California are an important consequence of climate change, severely affecting freshwater resources and environmental balance. Wildfires lead to reduced water resources, impacting agricultural water use and irrigation infrastructure, and affecting water quality through increased sediment and pollutant loads. The 2018 Camp Hill Fire contaminated local water sources, and the rebuilding process has increased demand for water resources, exacerbating resource constraints. Global warming has lengthened wildfire seasons and increased fire intensity, leading to increased pressure on freshwater resources. By analyzing the impacts of climate change on freshwater resources, this paper hopes to draw public attention to environmental protection and provide a reference for gradually optimizing ecosystems and creating a healthy living environment.

Projected changes in forest fire season, the number of fires, and burnt area in Fennoscandia by 2100

Abstract. Forest fire dynamics are expected to alter due to climate change. Despite the projected increase in precipitation, rising temperatures will amplify forest fire risk from the present to the end of the century. Here, we analysed changes in fire season, the number of fires, and burnt area in Fennoscandia from 1951 to 2100. Regional simulations from the JSBACH–SPITFIRE ecosystem model (where SPITFIRE stands for SPread and InTensity of FIRE) were performed under two climate change forcing scenarios (Representative Concentration Pathway (RCP) 4.5 and RCP 8.5) and three global climate driver models (CanESM2, CNRM-CM5, and MIROC5) with a 0.5° resolution. Simulations were forced by downscaled and bias-corrected EURO-CORDEX data. Generally, as a consequence of the projected longer fire season and drier fuel, the probability of fires is projected to increase. However, changes in fire season, the number of fires, and burnt area are highly dependent on climate projections and location. The fire season is estimated to increase on average from 20 ± 7 to 52 ± 12 d, starting from 10 ± 9 to 23 ± 11 d earlier and ending from 10 ± 10 to 30 ± 16 d later, compared to the reference period (1981–2010), by the end of the century (2071–2100). The results for Finland indicate a change in the number of fires, ranging from −7 ± 4 % to 98 ± 56 %, and a change in burnt area, ranging from −19 ± 24 % to 87 ± 42 %. These findings contribute to a better understanding of potential changes in the future fire seasons of northern Europe.

Late Glacial and Holocene history of climate, vegetation landscapes and fires in South Taiga of Western Siberia based on radiocarbon dating and multi-proxy palaeoecological research of sediments from Shchuchye Lake

Abstract To investigate long-term relationships between climate, vegetation, landscape geochemistry and fires in the boreal forest zone of Western Siberia, a sediment core of 345 cm was collected from Shchuchye Lake (located in south taiga zone of southeast part of West Siberian plain) and investigated by spore-pollen, radiocarbon, LOI and charcoal analyses. Quantitative palaeoclimate was reconstructed based on pollen data. Investigation revealed 13.2 cal ka history of vegetation, climate, landscapes and fires. In the dry climate of Late Glacial, the landscape was treeless. Continuous permafrost existed in the soil. In the middle of the YD cooling 12.4–12.2 cal ka BP, our data showed warming that caused degradation of permafrost in soils and settlement of spruce in moist places. Later, thawing and accumulation of moisture in a local lowering in relief increased and a lake was formed. With the beginning of the Holocene, the climate sharply changed to warmer and wetter. Intensified surface flow caused accumulation of mineral and carbonate fraction in the lake. Dense birch forests spread on drylands. As a result, the leaching regime initiated the formation of podzols in the soil. At about 10.0 cal ka BP, Scots pine (Pinus sylvestris) quickly spread in the area of investigation. Fires became more frequent and more intense during the dry Late Glacial time, sharply decreasing with increased precipitation in the Early Holocene, and again moderately increasing with spread of pine forests in the mid Holocene. With the transition to Late Holocene (after 6.0 cal ka BP), the intensity of regional background fires and number of local fires decreased.

Characterizing the Wildfire Patterns in the Marromeu Complex Using Remote Sensing Data

Objective: To caraterize the wildfire regime in the Marromeu Complex between 2002 and 2019. Method: Data from the MOD14 Collection 6 sensor, pertaining to thermal anomalies (MCD14ML, MCD64A1) corresponding to hot spots and burned areas, were used on a monthly basis. Only pixels with a reliability of 80% or higher were considered. Patterns of hot spots, burned area, density, intensity, frequency, and seasonality of fires were analyzed. Data processing was conducted using ArcGIS 10.8. Results and Discussion: A total of 12,227 hot spots were identified, covering 73% of the burned area. The annual average burned area was 24%, with densities ranging from moderate to very high. The fires showed low intensity across most of the Complex, with an average fire frequency of 2 to 3 times per year, and the highest fire records were observed in September. These findings are analyzed within the theoretical framework, emphasizing the implications of temporal and spatial variations in fires and their potential causes and environmental impacts. Implications of the Research: This study offers insights into wildfire management and emphasizes the necessity of fire management strategies in the Marromeu Complex. The implications include enhancing management plans and mitigating environmental impacts associated with fires. Originality/Value: This study contributes to the literature by providing a detailed characterization of the fire regime in the Marromeu Complex. The research is relevant as it offers new information on fire dynamics and their variations over time, which could impact management practices and environmental policies.

A novel proxy for energy flux in multi-era wildfire reconstruction

Escalations in wildfire activity are of significant global concern, particularly within vulnerable wetland ecosystems integral to natural carbon sequestration and climate change mitigation. Our understanding and management of future wildfire activity may be better contextualised through the study of historic and ancient fire records, independent of human influence. Methods of study include ‘geothermometry’ - approximating ancient fire intensity from temperature-dependent changes in the chemistry of fossil charcoal. Though well established in their relation to experimental charcoalification, these methods still fail to quantify the true intensity of ancient fires, as a measure of energy release. As a result, their applicability, and contributions to the characterisation of modern fire activity, remain uncertain. Here, we present a novel measure of wildfire energy release, as a proxy for true intensity, through the co-application of cone calorimetry and Raman spectroscopy of charcoal. By applying a range of wildfire heat fluxes to variable peatland fuel mixes, this research demonstrates the complexity in correlating fire behaviour and charcoal microstructure. Further statistical analyses suggest a correlation between spectroscopic results, measures of CO and CO2 release, and fire severity. This offers a principal measure of ancient wildfire intensity, consistent with modern practices in wildfire modelling, monitoring, and management.

Geo-Fenced Aerial Fire Response System

Purpose: We aim to create a prototype of a fire extinguisher drone equipped with advanced geo-fencing technology explicitly designed for use in high-rise buildings. This drone will be capable of both ground movement and flight, allowing it to quickly navigate narrow spaces and difficult-to-reach areas. Methodology: The study involves an in-depth analysis of various drones, features, and geo-fencing to develop a prototype for precise and targeted fire suppression. The aim is to minimize the damage caused by fires and improve overall safety by enabling swift intervention, particularly in confined or elevated locations where traditional firefighting methods may face challenges. Findings: The prototype drone, equipped with geo-fencing capabilities, has demonstrated its ability to be efficiently deployed within specific, pre-defined areas, significantly improving its precision and effectiveness in targeted fire suppression. This feature ensures that the drone operates only within designated zones, reducing the risk of interference or wandering into unsafe areas. The drone is controlled remotely, allowing it to fly freely and access hard-to-reach locations quickly. A small surveillance camera mounted on the drone enhances its effectiveness by providing real-time visuals of the fire's location and intensity. This capability allows operators to assess the situation more accurately and deploy the necessary response measures, making the drone a powerful tool for modern firefighting operations. Unique Contribution to Theory, Practice and Policy: The findings from this prototype provide valuable insights that can shape the future of fire response mechanisms and drone designs. The drones can target fires while minimizing risks to firefighting personnel, and they can potentially revolutionize emergency response strategies. The ability to remotely control drones, equipped with geo-fencing and surveillance capabilities, reduces the need for human intervention in dangerous situations and improves the speed and accuracy of fire suppression efforts. Furthermore, this technology can be applied to detect and combat wildfires, helping to minimize their destructive impact by enabling quicker detection and targeted responses in remote or difficult-to-access areas. These advancements pave the way for safer and more efficient firefighting methods in the future.

Computational analysis of wildland fire resistance for transmission line tower

Finite element (FE) analysis of the transmission towers under a fire event and the accompanying wind is presented. Several key aspects (including temperature-dependent non-linear material properties, geometric non-linearity, member eccentricity due to the single-leg bolted connection, and the temperature-dependent connection behaviour in both the axial and the rotational directions) are considered. A quasi-static analysis is also employed in the FE model using the explicit solver available in Abaqus. The member temperature variation during a realistic fire event is derived analytically based on the fire intensity and the resultant vertical gas temperature distribution so that the effect of the realistic wildland fire can be input as a member temperature profile. First, fire design guidance in terms of the most critical heating and wind pattern, as well as the effect of fire-affected heights are provided based on the case study results. Then, further fire analysis is carried out to investigate the most critical fire scenario and to evaluate the vulnerability of the tower during a realistic fire event. Lastly, an evaluation of a commonly used spray-on thermal insulation and its effectiveness in reducing the member temperature and preserving ultimate strength during a catastrophic wildland fire event are presented. The FE simulations revealed that a 45-degree wind associated with partial side heating leads to a more critical degradation of the overall strength, whereas the effect of fire height is less obvious. In terms of the fire scenario, a longer fire duration associated with a slower wind is more critical for the fire resistance/rating.

Impact of Debris Removal Post-Wildfires on Pavement Fatigue and Rutting Lives: Case Studies of California’s Camp and Carr Fires

Between 2017 and 2018, California experienced a series of four devastating fires, including the Camp and Carr Fires, which ranked among the most destructive fires in U.S. history. During these fires, roads were critical in the evacuation, rescue operations, goods transportation, and access to critical services. Additionally, postfire, road infrastructure became crucial for removing hazardous and nonhazardous waste from fire-affected areas to major landfills and recycling facilities. Despite the significance of pavements in this process, previous studies have not quantitatively assessed the potential damage caused to pavements by the additional trucks used in debris removal operations. This research aimed to address this knowledge gap by collecting precise traffic data for the routes taken to waste management facilities, including data on the number of trips involved in debris transportation. The traffic information was then utilized to calculate changes in equivalent single axle loads and traffic index values for pavement design. Pavement structures were obtained from the available core database. Pavement simulation results showed that of the nine studied highways, only one exhibited a reduction in cracking life of about 2 years. However, Skyway, the main artery in the town of Paradise, demonstrated a significantly accelerated fatigue cracking failure by 14.3 years. A sensitivity analysis of fire intensity showed other highway sections that were structurally adequate could be affected by larger fires. The presented methodology could be used in traffic planning as part of debris management operations to avoid vulnerable pavement sections.

Quantitative Study of Thermal Response of Timber–Concrete Composite Structures Under Traveling Fire Using Energy Equivalence Method

ABSTRACTThe time equivalent method can be used to quantify the fire intensity of a traveling fire into the time of action of the standard fire, which in turn can be used to assess the extent of damage to a structure under a traveling fire. However, an effective time equivalence method for timber structures has not been developed yet. Therefore, this paper proposed an energy‐based time equivalent method, referred to as the “energy equivalence method (EEM)”, for evaluating the fire resistance of timber structures under traveling fire, and validates its effectiveness through a series of fire tests. The results demonstrate that the EEM effectively quantifies the fire intensity endured by glulam under traveling fire as the equivalent exposure time under the standard fire. Furthermore, the EEM was utilized to investigate the damage behavior of a single‐layer Timber‐Concrete Composite (TCC) frame under traveling fire. The results reveal variations in the fire intensity experienced by the structure at different locations under the same traveling fire scenario, with the most severe damage occurring at a position 40% relative to the ignition end. The fire scale determines the non‐uniformity of the fire intensity and the extent of structural damage, as smaller‐scale fires (fire sizes between 10% and 40%) not only result in significant variations in damage levels at different locations but also have a more adverse impact on the structure. In fire safety design, the selection of standard and traveling fire design methods should be based on the fire scale.

Early-successional species show higher tolerance of drought than late-successional species across Europe

Climate change is exacerbating forest disturbances through more frequent and more intense droughts and fires, undermining their ability to recover from such disturbances. The response of fast-growing early-successional species to drought is poorly understood, despite their key role in ecological succession and their ability to enhance ecosystem resilience. Here, we compared the growth responses to drought events of three early-successional species (silver birch, black poplar, and Scots pine) with that of one late-successional species (European beech) across their natural distribution ranges in Europe. We used tree-ring widths of 6340 trees from 109 forest sites to establish species-specific tree-ring chronologies. We then used multiple linear regression to analyze which climatic or growth variables (pre-drought growth and growth during drought) best explained the tree responses to drought. Silver birch, Scots pine, and black poplar showed superior drought tolerance, with a slight, non-significant growth reduction under drought, whereas European beech showed a significant decrease in growth. The variables that influenced growth during and after the drought were species-specific. Annual precipitation and growth variables were key predictors of post-drought growth for Scots pine, black poplar, and European beech. Scots pine and silver birch grew better with increasing latitude, i.e., in Northern Europe than in Central Europe, while European beech and black poplar showed more growth at sites with high precipitation during the vegetation and dormant period, respectively. This study provides insights into the drought tolerance of early-successional species and highlights their ability to promote ecological succession and facilitate the transition to drought-resistant, late-successional forest ecosystems.

Comparison of different geometry trees in fire simulation

AbstractWildfire simulations can help to better understand the dynamics and effects of forest fires. The basis of wildfire simulation is the tree-burning simulation. In this paper, the fire simulation of 7 different geometry Hungarian trees in the case of arson is presented. It was observed that the trees were burned down fast. The maximum mass loss rate and maximum heat release rate were larger as the tree was larger. The largest intensity fire could be observed in the case of the smallest tree. The maximum temperature was higher in the case of a large crown diameter. The maximum aerosol reached high pollutant concentrations. In the case of large crown height, the maximum CO2 concentration was higher. The results presented in this paper can be the basis of the following forest fire simulations.

Quantifying global warming potential variations from greenhouse gas emission sources in forest ecosystems

Forest ecosystems play a crucial role in regulating greenhouse gas (GHG) emissions and mitigating climate change. This research aimed to evaluate the GHG emissions of various sources within forested ecosystems and assess their respective contributions to global warming potential (GWP), vital for developing more targeted strategies to mitigate climate change, shaping climate policies, carbon accounting, sustainable forest management, and advancing scientific comprehension of ecosystem-climate dynamics. The study comprehensively analysed carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions EDGAR data of deforestation, fires, and natural processes such as organic soil decomposition within forested ecosystems. The assessment quantified the CO2 equivalent emissions for each category from 1990 to 2022 and forecasted till 2030. Our forecast shows that CO2 emissions from deforestation could reach between 3,990 and 4,529 metric ton (Mt) by 2030, with forest fires contributing an additional 750 Mt. Forestland CO2 absorption is expected to decline to -5134.80 Mt by 2030. There is uncertainty surrounding the forecasts for Organic soil CO2 (829.78 Mt) and Other land CO2 (-764.53 Mt). In addition, deforestation was a significant contributor to CO2 emissions, with a GWP ranging from 4000 to 4500, highlighting the complex interplay between natural processes and human activities in shaping atmospheric warming patterns. Additionally, forest fires emit a complex mix of GHGs. The potency of these gases in warming the planet varies considerably, with CH4 exhibiting a GWP range of 500 to 700 Mt CO2 equivalent, and CO2 ranging from 900 and 1350 Mt. These variations depend on fire intensity and its overall impact on the climate system. Forestland acts as powerful carbon sink, capturing atmospheric CO2 with negative GWP values between -7000 and -6000. Researchers suggest a multifaceted strategy such as stricter enforcement of sustainable forestry regulations, investing in projects that promote carbon sequestration, and reforestation. Additionally, advancements in drone technology, satellite imagery, remote sensing and advanced data analytics can aid in detecting and mitigating climate change impacts, ultimately paving the way for carbon neutrality.Graphical

Spatiotemporal variation of polycyclic aromatic hydrocarbons in Tibetan lake sediment cores reveals the influence of forest fires

Despite declining anthropogenic emissions of polycyclic aromatic hydrocarbons (PAHs) due to global control strategies, forest fire emissions have been increasing, significantly affecting PAH dynamics in global sinks. This study investigated the spatiotemporal variations of sedimentary PAHs in three Tibetan lakes—Yiong Tso, Yamdrok Yumtso, and Urru Tso—to determine the influence of forest fires on PAH levels and historical trends. Yiong Tso Lake, located in a fire-affected watershed, exhibited the highest PAH concentrations (average of 43.4 ± 25.7 ng/g) with significant fluctuations since the 1920s, peaking in the 1960s (46.3 ng/g) and 1980s (91.3 ng/g), corresponding to periods of intense forest fires. This pattern aligned with source contribution estimates using the modified Cohen's d (mcd), indicating the dominance of forest fires as a PAH source until the 1990s. PAH concentrations decreased with increasing distance from the southeastern Tibetan Forest, as observed in Yamdrok Yumtso (average of 36.1 ± 19.9 ng/g) and Urru Tso (average of 16.4 ± 6.9 ng/g). Temporal variations in PAH concentrations and mcd values from these lakes also reflected a response to forest fires during the 1960s, suggesting a widespread influence of forest-fire-derived PAHs across the plateau. The impact of forest fires on sedimentary PAHs was expected to persist for decades, with an estimated half-life of approximately 11–12 years. These findings highlight significant emissions of PAHs from forest fires in the Tibetan Plateau, potentially transforming regional PAH dynamics and influencing global cycling.

Dual-agent intelligent fire detection method for large commercial spaces based on numerical databases and artificial intelligence

Fires in commercial buildings can lead to significant casualties and property damage. Thus, rapidly and accurately identifying the source of a fire and its intensity is crucial for guiding rescue operations. This study aims to explore the use of distributed fiber optic temperature sensing systems, combined with deep learning algorithms, to predict key information about fires in commercial buildings, including the location of the fire source, the intensity of fire development, and the critical planar distribution of carbon monoxide. Based on the Fire Dynamic Simulation (FDS) data, a dual-agent model was developed, and with a sensor sampling interval of 3 s, 30 s of historical data achieved prediction accuracies of 94.23 % for fire intensity and 99.28 % for fire location. Upon reducing the intervals for fire location, the accuracy reached 93.56 %. Additionally, the Random Forest algorithm for mapping carbon monoxide distribution demonstrated an overall Mean Absolute Percentage Error (MAPE) of 5.87 %. Within the 0–150 ppm range, the MAPE was 2.46 %, far below the error levels of existing CO sensors. The database configurations and the sensors' spatiotemporal arrangement were also optimized to rapid and reliable fire prediction. This research demonstrates the feasibility of using artificial intelligence for critical fire scene information detection.

When do contemporary wildfires restore forest structures in the Sierra Nevada?

BackgroundFollowing a century of fire suppression in western North America, managers use forest restoration treatments to reduce fuel loads and reintroduce key processes like fire. However, annual area burned by wildfire frequently outpaces the application of restoration treatments. As this trend continues under climate change, it is essential that we understand the effects of contemporary wildfires on forest ecosystems and the extent to which post-fire structures are meeting common forest restoration objectives. In this study, we used airborne lidar to evaluate fire effects across yellow pine and mixed conifer (YPMC) forests of California’s Sierra Nevada. We quantified the degree to which forest structures in first-entry burned areas (previously unburned since ~ 1900s) and unburned controls aligned with restoration targets derived from contemporary reference sites. We also identified environmental conditions that contributed to more restorative fire effects.ResultsRelative to unburned controls, structural patterns in first-entry burned areas aligned more closely with reference sites. Yet, across all burn severities, first-entry wildfires were only moderately successful at meeting targets for canopy cover (48% total area) and ladder fuels (54% total area), and achieving these targets while also producing tree clump and opening patterns aligning with reference sites was less common (16% total area). Moderate-severity patches had the highest proportion of restorative fire effects (55–64% total area), while low- and high-severity patches were either too dense or too open, respectively. Our models (and publicly-available mapped predictions) indicated a higher probability of restorative effects within 1 km of previous fires, within the mid-upper climate range of the YPMC zone, and under moderate fire intensities (~ 1–2 m flame lengths).ConclusionsFirst-entry wildfires can sometimes restore structural conditions by reducing canopy cover and ladder fuels and increasing structural heterogeneity, especially within moderate-severity patches. However, these initial fires represent just one step toward restoring dry forest ecosystems. Post-fire landscapes will require additional low- to moderate-intensity fires and/or strategic management interventions to fully restore structural conditions. In yet unburned forests, managers could prioritize mechanical treatments at lower elevations, early-season burning at mid to high elevations, and resource objective wildfires in landscapes with mosaics of past wildfires.

Enhancing Global Simulation of Smoke Injection Height for Intense Pyro‐Convection Through Coupling an Improved One‐Dimensional Plume Rise Model in CAM‐chem

AbstractThe impact of wildfire smoke is largely determined by the height where they are injected into the atmosphere. Current plume rise models tend to underestimate the high smoke injection heights because the previous models and configurations were mainly constrained and validated by the plume height observation from Multi‐angle Imaging SpectroRadiometer (MISR), of which most cases inject low within the planetary boundary layer (PBL). Here we retrieve smoke injection heights from intense pyro‐convections based on pyrocumulonimbus satellite images in PYROCAST data set alongside meteorological reanalysis. It largely augments the MISR data set with smoke injection heights up to the upper troposphere and lower stratosphere (UTLS). Constrained by both MISR and PYROCAST, we show that a scaling down of factor 0.2 to the entrainment efficiency parameterized in the one‐dimensional plume‐rise model (1‐D PRM, Freitas et al. (2010, https://doi.org/10.5194/acp‐10‐585‐2010)) significantly improves the model performance for high injection cases without compromising the accuracy of low injection cases. We also found that the fire intensity input can be obtained through a simplified dependence on the biome and biomass burning emission flux. While being unable to represent high cases before, the improved 1‐D PRM model predicts similarly well in injection heights both low near the PBL height and high into the UTLS. The improved 1‐D PRM is then coupled into Community Atmosphere Model with Chemistry (CAM‐chem). The coupled CAM‐chem‐PRM, when predicting injection heights in tests imitating real BB emission, exhibited consistent predictive capabilities with the standalone 1‐D PRM while saw a mere 15% increase of computation time.

Characterizing firebrands and their kinematics during lofting

Spot fires pose a major risk and add to the already complex physics, which makes fire spread so hard to predict, especially in the wildland urban interface. Firebrands can not only cross fuel breaks and thwart other suppression efforts but also directly damage infrastructure and block evacuation routes. Transport models and computational fluid dynamics tools often make simplifications when predicting spot fire risk, but there is a relative lack of experimental data to validate such parameterizations. To this end, we present a field experiment performed at the University of California Berkeley Blodgett Research Forest in California where we recorded the flame and firebrands emanating from a nighttime hand-drawn pile fire using high-frequency imaging. We used image-processing to characterize the fire intensity and turbulence as well as particle tracking velocimetry to measure ejected firebrand kinematics as they are lofted by the plume. We further collected embers that settled around the fire at varying distances and measured their size, shape, density, and settling distributions. We also examine existing physics-based time-averaged models of firebrand lofting and note discrepancies between such models, often used due to their speed and simplicity, and our experimental observations. Finally, we discuss some implications our observations could have on future modeling efforts by considering the time-dependent fire dynamics, intermittency in the plume turbulence, and in the firebrand generation rate. To the best of our knowledge, these are the first in situ observations of firebrand generation and lofting from representative fuels, addressing a major source of data gap and uncertainty in the wildland fire literature.