bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyrocumulonimbus Firepower Threshold: Selected learnings from the ‘Black Summer’ real-time trial
Authors: Tory Kevin , Peace Mika
Published: October 2022

Pyrocumulonimbus (pyroCb) clouds are difficult to predict and can produce extreme and unexpected wildfire behavior that can be hazardous to fire crews. Many forecasters modify conventional thunderstorm diagnostics to predict pyroCb potential, by adding temperature and moisture increments to represent smoke plume thermodynamics near the expected plume condensation level. An alternative approach is to anticipate the minimum firepower required to generate pyroCb for a given atmospheric environment.This concept, termed the pyroCb firepower threshold (PFT), requires only atmospheric information, removing the need for subjective estimates of the fire contribution. A simple approach to calculating PFT was presented by Tory and Kepert (2021) that incorporates only basic plume-rise physics, and yields an analytic solution for the minimum heat flux required to enter the base of the plume for pyroCb to form. This version takes into consideration the magnitude of any inversion or stable layer the smoke plume must penetrate, the height the smoke plume must rise before sufficiently buoyant cumulus clouds form in the smoke plume, and it incorporates the impact of wind on plume rise via the Briggs plume-rise model. This PFT also offers important insight into plume behavior and pyroCb formation. Many assumptions are made to close the equations and to maximise simplicity. Two of these assumptions are questioned in this paper following the investigation of two deep, moist pyro-convection cases that occurred during â€˜Black Summerâ€™ (southern Australia, September 2019â€”March 2020). The first assumption, consistent with many thunderstorm diagnostics, is that the moist (cloudy) plume is non-entraining, and the second assumption is that the plume is positively buoyant when it saturates and remains buoyant until it rises beyond the -20 â„ƒ level of the atmosphere. The first assumption underpredicts the fire-power required and the second assumption can overpredict the necessary firepower, since a vigorous plume may have sufficient kinetic energy to penetrate stable layers or capping inversions. Procedures are introduced to address these limitations.
Spatiotemporal analysis of fire danger extremes in Europe between 1980 and 2019: Preliminary results
Authors: Giannaros Theodore M. , Papavasileiou Georgios
Published: October 2022

This work summarizes preliminary results of a spatiotemporal analysis focusing on changes in the occurrence of fire danger extremes in Europe between 1980 and 2019. Extreme danger days were defined based on the daily severity rating exceeding the locally defined 95th percentile. For the 2001 â€“ 2019 period, we show that extreme fire danger days and total burnt area have a positive relationship across Europe, albeit stronger in the eastern half of it. Trend analysis results indicate that extreme fire danger days have overall increased in Europe, with the largest increases found in the north-eastern regions. Further, we illustrate that these increases may be related to abrupt shifts in the means, especially over the south-west Mediterranean, and central and north-eastern Europe. These shifts took place primarily during the 1990s, marking large increases in the mean annual number of extreme fire danger days before and after the years of change.
The geography of forest fires in Greece: fire resilience vis-à-vis management crises
Authors: Kalabokidis Kostas , Palaiologou Palaiologos
Published: October 2022

Greece has an ever-increasing appeal for establishment of new and/or expansion of existing human settlements that in turn cause pressures on the natural environment, increasing the fire risk and resilience at a landscape level. A multitude of Mediterranean-type of ecosystems exist in the country, ranging from low shrubs and coniferous woodlands on coastal sites to high-elevation conifer and broadleaf forests. Fire plays a critical role on how these ecosystems were formed and function. Due to the topography, land uses, numerous islands, extensive coastlines and local microclimates, we find either broad zones with similar fire-related characteristics or enclaves where unique interactions with landscape fires prevail. We described the fuel and fire schemes in Greece as formed by different combinations of topography, weather, vegetation and human activity. A geographical context for this analysis was provided by examples of recent wildfires occurred in Greece during the 21st century, which re-shaped the landscape and affected in multiple ways the natural environment and human settlements from severe fire effects. In addition, we showed how these wildfires created crises that drove fire management policies; and we illustrated how fuels and wildfires should be managed based on their respective fire regimes and expected fire effects. Finally, we briefly reviewed future implications for wildfire management from the cumulative effects of climate change, urban sprawl and unmanaged forest growth.
Validation of the Small World Network Model on a prescribed burning
Authors: Hamamousse Nadjet , Zekri Nouredine , Kaiss Ahmed , Mosbah Omar
Published: October 2022

This work aims to validate the Small World Network Model by comparing the numerical predicted rate of spread results to those obtained from a prescribed burning in the city of Oran in Algeria using Pinus Halepensis needles. In the first part of the experimental tests pine needles partially dried using microwave oven and climatic chamber were used. Fire propagation tests were then realized at different fuel moisture contents. In the second part of the tests, dead Pinus Halepensis needles were used in order to evaluate the effect of the terrain slope on fire spread. This model may be used to simulate the fire patterns both in homogeneous and heterogeneous landscapes. This model takes into account both the deterministic effects induced by the flame, and the probabilistic long range effects due to the spotting process of firebrands. Therefore, it combines as well the advantages of network models and those of macroscopic semi-physical models.
A mechanistic live fuel moisture model
Authors: Jolly W. Matt , Conrad Elliott T.
Published: October 2022

Wildland fires are a common global disturbance and many of these fires burn through mixtures of living and dead vegetation. Live fuels are unique because they regulate biomass and water content actively through processes such as photosynthesis or transpiration. The main goal of these processes is to maintain the growth and maintenance demands of the plants while minimising water loss. Historically, live fuel dynamics were assumed to be only driven by evaporative or drying processes and little attention was paid to the interplay between carbon and water dynamics. Here we present a mechanistic model of live fuel moisture (LFM) which is a critical component of live fuel flammability. The model decouples LFM into metrics that are easy to measure such as particle density, surface-area-to-volume ratio, leaf mass area and relative water content. Each metric serves as a proxy for important components of the seasonal water and carbon cycle or to capture inter-species variations in physical properties.We evaluate this model using field measurements of physical and chemical characteristics for a Douglas Fir (Pseudotsuga menziesii), a common intermountain US tree species that commonly burns in crown fires. This simple, mechanistic model was effective at characterising the seasonal variations in LFM across both new and old foliage as a simple function of foliar density and relative water content (r2=0.984,p < 0.05) . Finally, we show how this decoupled model can be used to more appropriately parameterize a 3-dimensional computational fluid dynamics based fire behaviour model to represent an appropriate live fuel moisture as the combined effects of biomass and moisture variations on canopy flammability.
Fire Weather Warnings in Croatia
Authors: Kozarić Tomislav , Hojsak Tomislava , Mokorić Marija
Published: October 2022

Vegetation fires are among the most dangerous natural hazards. In Croatia, they are most common on the Adriatic coast and in the areas near the Adriatic, especially in summer when the peak of the fire season occurs. Meteorological risk of vegetation fires in Croatia is primarily assessed with the Canadian Forest Fire Weather Index and derived fire danger. However, due to the rare spatial and temporal availability of these data as well as the effects of climate change resulting in frequent enhanced fire danger during the summer, the need for additional risk assessment tool has emerged. In that sense, the fire weather warnings were introduced ten years ago and since then have been constantly improved and adapted to the needs of the firefighting community. The aim is to warn of weather conditions that can lead to the rapid spread and unpredictable behavior of the vegetation fires. As a basic condition, fire weather warnings are issued when the fire danger classes from the Canadian Forest Fire Weather Index are high and very high. Except the meteorological parameters of the Fire Weather Index, the most important of which is wind, the behavior and spread of vegetation fires can be further influenced by atmospheric turbulence and instability in the dry air near the ground and in the lower atmosphere. These parameters also depend on the orography of the terrain and are not included in the Fire Weather Index. Two years ago, three levels of warnings were defined, the thresholds of which depend on the values and duration of wind, turbulence and instability. In addition to the detailed explanation of the method for issuing fire weather warnings, the paper presents textual and graphical warning examples, describes five critical fire weather patterns when conditions for issuing warning are the most common, and in the end gives a brief overview of warnings statistics and the most recent evaluation. According to the feedback from the firefighting community, the warnings proved to be important in the organization of supervisory and preventive activities, as well as fire suppression activities in case of vegetation fire ignition. The evaluation also shows that most of the significant vegetation fires burned in the days and at the locations for which warnings were issued.
From fire danger to fire risk: an integrative framework for near-term wildfire risk forecasting
Authors: Jolly W. Matt , Freeborn Patrick
Published: October 2022

Wildfires are a common global disturbance. Many of these fires fill important ecosystem roles but others must be suppressed to prevent loss of life or property. Decision support tools can provide critical information to support effective wildfire management but the many components of these tools lack a supporting framework to integrate risk components to produce effective and useful wildfire risk forecasts. Here we present a framework to support wildfire preparedness and response decision making that incorporates both static and dynamic components of wildfire hazard to produce risk forecasting. Static model components provide a time-invariant ignition probability for both human and natural caused ignitions and are developed using topographic and fuel quantity metrics. Dynamic model components are evaluated using a combination of fire danger rating indices from the new US National Fire Danger Rating System Version 4.0 released in 2016 and the newly derived Severe Fire Danger Index. When combined together, we demonstrate the effectiveness of this model forecast system to predict the spatial and temporal locations of new wildfire ignitions across large areas using a blend of high, moderate and low resolution spatial terrain, fuels and weather forecast data. We demonstrate components of this framework across the United States and Northern South America specifically across Colombia, Ecuador and Peru. This work will improve our ability to leverage modern fire danger rating systems with over conventional wildfire risk assessments to provide better decision support products throughout the world and these products have the potential to reduce wildfire impacts to firefighters and communities.
Fuel Moisture Content in Croatian wildfire spread simulator AdriaFirePropagator
Authors: Stipaničev Darko , Bugarić Marin , Bakšić Nera , Bakšić Darko
Published: October 2022

Fuel moisture content (FMC) is the mass of water contained within vegetation in relation to the dry mass. It is one of the most important variables in all wildfire prediction and spread simulation models. FMC has great influence on wildfire ignition and combustion. For accurate wildfire spread simulations and wildfire risk index estimations, fuel moisture is a very important input variable. Since 2016, Croatian firefighters in everyday practice use Web based System for wildfire behaviour modelling and wildfire spread simulation named AdriaFirePropagator. The simulator is based on semi-empirical Rothermelâ€™s surface fire spread model for wildfire behaviour modelling and cellular automata for wildfire spread simulation. Fuel moisture, both live and dead is a very sensitive parameter in wildfire behaviour modelling. Live fuel moisture defines the moisture content of live fuels and dead fuel moisture is defined as moisture of dead fuels with time-lag of 1 hour, 10 hour and 100 hours. In Croatia there is no organised service for daily measurement of fuel moisture content, so values of these variables has to be estimated from meteorological parameters. This paper compares three approaches to fine dead fuel estimation, all implemented in AdriaFirePropagator. The first one, used in most wildfire simulation software, was based on standard mathematical models that relate air temperature, air humidity, 24-hours rainfall and wind speed with fine dead fuel moisture (FFMC). The second one was based on standard Fire Behavior Analysis Tables (FBA Tables) and the third one was based on intensive experimental research of dead fine fuel moisture content of Aleppo pine (Pinus halepenses Mill.). After intensive experimental research new Croatian fine dead fuel models PhFFMC was developed, tested in selected pine species stand and applied in AdriaFirePropagator for fuel regions where this pine species dominate. Croatian model is much better correlated with experimental data, therefore for more accurate wildfire simulations, similar models have to be developed also for other typical vegetation fuel types.
Generic burning rate curve for porous fuel beds
Authors: McAllister Sara , Grenfell Isaac , Finney Mark
Published: October 2022

A new wildfire spread model is being developed to alleviate many of the limitations of current operational models. This new model consists of sub-models for ignition, burning and heat release rate, and heat transfer. Unfortunately, the factors that control the burning rate of wildland fuels are not well understood. In this work, we use an extensive database of experimental data with wood cribs to examine curve forms that can be used to describe the time-dependent nature of the burning rate of porous fuel beds. Fifty crib designs and 148 individual mass data curves of cribs burned with unrestricted airflow were available for analysis. Both a power law and a Weibull-distribution-like curve are shown to capture the main shape of the experimental data. Further work will incorporate data with restricted airflow, wind, and moisture content.
Improved prediction of drought for wildland fire danger rating in Canada
Authors: Hanes Chelene C. , Wotton Mike , Woolford Douglas G. , Bourgeau-Chavez Laura , Bélair Stéphane , Martell David , Flannigan Mike
Published: October 2022

Canadian fire management agencies track drought conditions using the Drought Code (DC). The DC is one of three fuel moisture codes in the Fire Weather Index System, which is part of the Canadian Forest Fire Danger Rating System. The DC represents the moisture of deep organic layers (15-18 cm nominal depth) and is used operationally to assess potential lightning ignition holdover, persistent deep smoldering, and mop-up problems. As the climate changes and drought conditions arise more frequently, our understanding of drought and how to measure it become more important. Determining what the DC means in areas without deep organic soils is a question commonly proposed by fire operations personnel. Recent studies have indicated that some more complex models (e.g. the Canadian Land Data Assimilation System â€“ CaLDAS) may provide added intelligence about the fire environment and drought conditions, something that has not been explored in Canada. To shed light on these questions we carried out field studies in the provinces of Alberta and Ontario. Four field sites were included in our study, two in Alberta near Edson and Red Earth Creek, and two in Ontario near Dryden and Chapleau. At each of the seven plots within these four sites, we installed 8-12 water content reflectometry (WCR) probes at two different depths. The probes were installed from the surface through the organic layers, and in some cases, into the mineral soil. Overall, our results indicated that the simple DC model predicted the moisture content of the deeper organic layers (10-18 cm depths) well, even compared to the more complex CaLDAS model. The WCR probes at these depths, exhibited good agreement with how the DC model estimated moisture changes. The DC may therefore be representative of changes in moisture content in a wide range of depths and soil horizons. Issues with model inputs, particularly missed precipitation events and incorrect DC spring starting values, had a greater influence on DC model fit than other factors. Calibration and validation of the CaLDAS model to mineral soils may be the cause of its consistent under prediction of organic layer moisture.
Lidar Instrumentation for the California Fire Dynamics Study
Authors: Makowiecki Amanda , Strobach Edward , Baidar Sunil , Lareau Neil , Clementsu Craig , Brewer W. Alan
Published: October 2022

The California Fire Dynamics Study (CalFiDE) is a collaborative effort between the Chemical Sciences Laboratory (CSL) at National Oceanic and Atmospheric Administration (NOAA), Wildfire Interdisciplinary Research Center (WIRC) at San Jose State University (SJSU) and the University of Nevada Reno (UNR), to investigate wildfire dynamics in Northern California in late Summer and Fall 2022. Further information on the instrumentation and scope of this study can be found in the Valero et al. short paper. During CalFiDE, the contributing organizations plan to deploy four Doppler lidar systems in addition to infrared imaging and chemical measurements to quantify the fire dynamics and atmospheric coupling of large scale wildfires. These systems will be installed on a range of mobile platforms including; a Twin Otter aircraft, pickup trucks, and trailers. The mobile ground based installations allow researchers to rapidly deploy the systems to areas of interest during the study, while the aircraft installation will cover a larger range of spatial scales. Systems will operate in scanning modes to quantify 3D winds, vertical stares to resolve fine scale vertical velocities, and coordinated scans where the measurement volumes of nearby systems are overlapped to provide high resolution measurements of 3D winds. The coordinated scanning technique will be used to target fine scale features within fire plumes such as helical updrafts, counter-rotating vortices, and inflow/outflow dynamics. Collectively these lidar observations will provide validation data sets for simulated fire-generated winds.
Prediction of soil properties immediately after fire using SAR backscatter data
Authors: Fernández-Guisuraga José Manuel , Marcos Elena , Suárez-Seoane Susana , Beltrán-Marcos David , Fernández-Manso Alfonso , Quintano Carmen , Calvo Leonor
Published: October 2022

The physical sense of synthetic aperture radar (SAR) backscatter data is of particular interest for characterizing soil spatial variability in burned areas. The objective of this study was to evaluate the potential of SAR backscatter data in L-band (Advanced Land Observing Satellite-2; ALOS-2) for assessing fire effects on soil organic carbon, total nitrogen and available phosphorous immediately after wildfire in a burned landscape of the western Mediterranean Basin. ALOS-2 backscatter coefficients were used to estimate soil properties measured in the field in immediate post-fire situation through generalized linear models. The retrieval of soil properties from ALOS-2 L-band SAR backscatter data featured a high overall fit (R2 = 0.37-0.59) and low error (nRMSE = 12.7%-22.5%). ALOS-2 co-polarized channel showed the highest sensitivity to spatial variation in soil properties, and there were no noticeable under and overestimation effects. These results support the applicability of SAR sensors operating at long wavelengths for monitoring fire effects on soil properties, reducing data gathering costs within large burned landscapes.
Remote characterization of fire behavior during the FireFlux II experiment
Authors: Valero Mario M. , Kochanski Adam K. , Clements Craig B.
Published: October 2022

The FireFlux II field experiment was conducted on January 30th, 2013 in south-east Texas, USA, under high fire danger conditions. The experiment was designed to study the behavior of a head fire progressing through a flat, tall grass prairie, and it was informed by the use of a coupled fire-atmosphere model. Vegetation properties and fuel moisture were measured shortly before the experiment. Near-surface atmospheric conditions were monitored during the experiment using an elaborate meteorological instrumentation array. Fire behavior was observed through a combination of remote and in-situ sensors. Clements et al. (2019) presented the analysis of the experiment micrometeorology and in-situ fire behavior observations acquired using a thermocouple array. In this paper, we extend the study of fire behavior during the FireFlux II experiment with the analysis of remote sensing observations. Two thermal infrared and two visible cameras were deployed during the experiment. One thermal and one visible camera were mounted on a helicopter, whereas the other two cameras were installed on a 40-m-height tower next to the burn unit. The tower infrared camera covered a reduced area of interest coincident with the thermocouple array and it allowed monitoring the fire spread as well as measuring the spatially-resolved evolution of brightness temperature. Imagery collected from the helicopter allowed extending fire behavior measurements to the complete burn unit. While airborne IR footage was saturated and did not allow estimation of emitted radiant heat, its analysis allowed tracking fire progression through the plot and therefore estimating rate of spread and fire time of arrival. The existence of in-situ temperature observations provides an outstanding opportunity to validate remote sensing methodologies. In addition, the combination of remote observations with in-situ temperature measurements allows a comprehensive characterization of fire behavior, including spatially-resolved fire rate of spread and fire time of arrival, fire radiative power, Byramâ€™s fire line intensity, and air temperature during fire front passage. The current version of this paper presents preliminary results from this analysis. Such results demonstrate the usefulness of the selected datasets and the potential of the proposed methodology, encouraging further work. Possible applications of the resulting dataset include (i) the validation of existing fire behavior models that are able to predict any of the measured variables, (ii) the development of data-driven fire behavior models, and (iii) the investigation of the relative contribution of radiative and convective heat transfer mechanisms to fire spread.
Remotely sensed time series reveal varying levels of association between burned area and severity across regions in mainland Portugal
Authors: Gonçalves João , Marcos Bruno , Honrado João P.
Published: October 2022

Wildfires can pose severe threats to human lives and assets as well as for biodiversity at a global scale. Due to climate, land-use changes, and often inadequate forest management, wildfire regimes are also in transition, causing modifications in these disturbance events' spatial distribution, timing, size, frequency, and severity. In particular, increasing fire severity causes slower post-fire recovery times and a depletion in the resistance and resilience capacities which potentially trigger regime shifts in the state of ecosystems. Satellite remote sensing (SRS) Earth Observations (EO) allow us to characterize the ecological impacts of wildfires and assess spatiotemporal trends in fire severity. The SeverusPT project is currently pursuing the objective of harnessing SRS/EO time series to characterize wildfire severity and assess its impacts on ecosystems and human activities. Our primary objectives of this exploratory research paper are two-fold: (i) assess national and regional spatiotemporal trends in fire severity and burnt area, and (ii) evaluate if fire severity regionally scales up with the total burnt area. Satellite image time series (SITS) from Terra/MODIS were obtained to calculate fire severity through the Normalized Burn Ratio (NBR) and the difference between pre- and post-fire (Î”NBR). Trend analyses were employed to quantify fire severity and burned area spatiotemporal patterns. Linear regression assessed the association level between total burnt area by year/region (predictor) and fire severity (response). Preliminary results show that at a national level from 2001 until ca. 2008 - 2009 there was a general decrease in fire severity, followed by a reversal of this trend. This turning point has led to a general increase with new severity highs formed in 2017 and 2020. We also found wide variation in fire severity at the regional level (NUTS-III), and trend analysis display that most regions increased both in burned area and severity. Linear regression showed that burned area and fire severity are correlated despite this association being highly structured at the regional level, forming a continuous spectrum from highly area-severity coupled regions (e.g., AM Porto, MÃ©dio Tejo, Viseu, Coimbra, Alto-Minho) to less coupled ones (e.g., CÃ¡vado, TrÃ¡s-os-Montes, Alentejo). These results may support that the increasing amount and size of burnt area will scale up into higher fire severity for specific regions. These preliminary results from the SeverusPT project show that MODIS image time series allow assessing the spatial variation and the temporal trends of fire severity in a standardized and synoptic fashion. Mapping fire severity, its spatiotemporal variation and addressing its environmental drivers are now more crucial than ever to understand its dynamics and support fire management and prevention.
Simple firefighting demand modelling and its use for estimation of the potential influence of fuel treatment scenarios on the number of required firetrucks on the island of Kythira, Greece
Authors: Xanthopoulos Gavriil , Athanasiou Miltiadis , Varela Vassiliki , Kaoukis Konstantinos , Xanthopoulos Panagiotis
Published: October 2022

The island of Kythira, in Greece, suffered a devastating forest fire that started on August 4, 2017. After that, it became evident that the location of the island, away from aerial fire suppression resources bases and with limited capacity for quick arrival of significant ground firefighting reinforcements, necessitates careful fire prevention and presuppression planning to avoid repetition of the disaster. The study presented here aimed to examine the adequacy of the available 13 firetrucks on the island to successfully carry out initial attack under similar conditions to those of 2017 and to evaluate what could be the effect of four alternative fuel treatment scenarios on reducing the potential of a future disaster. A map of the forest fuels on the island, a weather scenario similar to the conditions at the start of the 2017 fire, and the Digital Elevation Model (DEM) of the island were used with a fire spread simulator (G-FMIS) first to simulate the actual fire and to examine if it matches the observed fire spread in 2017. Once good agreement was verified, four fuel treatment scenarios were applied on the fuels. The accordingly adjusted fuel map was used for further simulations. The resulting fire perimeter growth, taking flame length into consideration, was examined against the capacity of ground forces (firetrucks) to control lengths of the perimeter using a simple but effective fire suppression model, that is based on an equation developed earlier for assessment of the effectiveness of such forces in Greece. The results showed that under broadcast grazing on the island the risk of escaped fires can be minimized, reducing the need for heavy aerial support in case of a fire.
Simulating wildland surface fire behaviour to support emergency management
Authors: Voltolina Debora , Cappellini Giacomo , Apuani Tiziana , Sterlacchini Simone
Published: October 2022

The recent upsurge in the incidence of extreme wildfire events, the expected impact of climate change on the frequency and severity of fires, and the progressive expansion of wildland-urban interface areas highlight the tangible need for improvement in our ability to predict, mitigate and manage the growing risk to which communities are exposed. The aim of this research is to contribute to deepen the knowledge on the spatial simulation of complex dynamics of wildland surface fire behaviour through the development and validation of a spatially distributed predictive model for the simulation of wildland surface fire spread intended for operational purposes. Given the position of one or more ignition points, the developed model allows to (i) obtain near real time dynamic estimates of the geo-environmental variables that control the fire spread, (ii) compute the direction and intensity of the maximum rate of fire spread in heterogeneous environments, and (iii) simulate the surface fire spread using agent-based models. The final aim is to provide competent authorities with timely information on the expected evolution of the flame front to optimise decision-making processes. The model, developed under synthetic conditions, is then applied to case studies recorded in the territory of the Autonomous Region of Sardinia, that offers institutional information on the ignition location, the evolution of the flame front, and the completed fire suppression activities, which are implemented in the model as well. Overall, the model showed a promising predictive capacity evaluated in quantitative terms of morphological matching between the observed and predicted fire spread patterns, returning more accurate results in areas with less complex morphologies and dominated by herbaceous rather than shrubby fuels. The model also made it possible to obtain accurate simulations in rapid processing times, compatible with its operational application as a tool for optimising and planning fire risk prevention and mitigation strategies and policies as well as fire management activities. Future research will be addressed at improving the predictive capacity of the model and estimating the propagation of the parametric uncertainty of the geo-environmental variables within the model.
Simulation of induced-wind-dominated fire on sloping terrain
Authors: Accary Gilbert , Fayad Jacky , Chatelon François-Joseph , Frangieh Nicolas , Awad Carmen , Meradji Sofiane , Marcelli Thierry , Rossi Jean-Louis , Morvan Dominique , Rossi Lucile
Published: October 2022

Using the fully physical model FireStar3D, a numerical simulation of an eruptive fire was carried out for a grassland on a slopping terrain (30Â° inclination) and a 10 m-open wind speed of 2 m/s. To reproduce the behaviour of a quasi-infinite fire front, periodic conditions were considered in the fireline direction. The simulation highlights the role played by the additional wind induced by the fire (that reaches about 5.8 m/s at 10 m above ground) and its feedback action on fire behaviour. This interaction results in the transition of the fire behaviour from a plume-dominated fire to a wind-dominated fire, and this goes along with a substantial increase of the rate of spread (from 0.454 m/s to 0.714 m/s) and of the fireline heat release rate (from 4.8 MW/m to 14 MW/m). The fire regime was characterized by Byramâ€™s convection number, based on the effective crosswind speed, that drops from 46.8 to about 3.8 once fire-induced wind takes effect on fire behaviour.
Spectral monitoring of a system for the rehabilitation of burned soils based on inoculation with cyanobacteria and microalgae
Authors: Gonçalves João , Marcos Bruno , Silva Márcia Bessa da , Conceição Inês , Pissarra João , Roque Jéssica , Tamagnini Paula , Melo Paula , Pereira Ruth , Honrado João
Published: October 2022

Inocula containing photosynthetic microorganisms such as cyanobacteria and microalgae can promote the formation of biocrusts, improving the soil properties and allowing ecosystem recovery. The GreenRehab project aims to develop a low-cost, eco-friendly, and easy-to-implement system to rehabilitate burned soils and protocols to evaluate the success of an ecosystem after-fire recovery. For this purpose, native cyanobacteria and microalgae were isolated from soil/biocrusts and tested, with selected strains being cultivated on a large scale. To evaluate the performance of the proposed rehabilitation system (based on the inoculation of native cyanobacteria and microalgae), we analyzed spectral data scanned from a portable visible/near-infrared spectrometer that indirectly estimates top-soil photosynthetic activity. Several spectral indices based on the normalized difference combination of spectral bands were calculated and compared for their ability to assess photosynthetic activity over time. Results showed that treatments with microalgae and cyanobacteria effectively enhanced photosynthetic activity, with Trichocoleus stimulating soil rehabilitation the most. Moreover, the best performing normalized difference index was the one combining the 660 nm and 860 nm wavelengths. Parallelly, very-high resolution imagery obtained from a UAV equipped with a multispectral camera is currently being tested to assess the performance of different inocula previously selected from microcosm experiments in environmental conditions closer to real ones found in post-fire scenarios. Preliminary results led us to develop an integrated protocol for image acquisition, radiometric calibration and photogrammetric post-processing. This allowed us to characterize baseline conditions in the test area, including geomorphology, vegetation and portray fine-scale patterns in greenness and photosynthetic activity. Overall, spectral measurements and indices from portable spectrometers and UAVs open the possibility of assessing which treatments exploited in the GreenRehab project effectively enhance soil rehabilitation and recovery from frequent fires. Such innovation may translate into other 'real-world' applications in ecology, forestry, and agronomy fields.
Structure characterization on Mediterranean forest stand using terrestrial laser scanning
Authors: Ferrara Roberto , Arrizza Stefano , Ventura Andrea , Arca Bachisio , Salis Michele , Arca Angelo , Masia Pierpaolo , Duce Pierpaolo , Pellizzaro Grazia
Published: October 2022

Forest stands plays an important role in Western Mediterranean ecosystems, their characterization it is needed for a whole comprehension of natural dynamics and for an efficient forestry management. The definition of the structural parameters of forest vegetation is a useful information for different environmental applications, such as studies on carbon dynamics, sustainable forest management, ecological studies, forest fuel studies and fire risk management. A precise description of the forest is particularly important for fire hazard mitigation planning because allows predictions of the potential fire behavior and its destructive effects. Obtaining detailed information on forest stand and canopy variables requires extensive, difficult, and laborious field campaigns. Remote and proximal sensing techniques for forest monitoring have become popular in recent decades. Specifically, Terrestrial Laser Scanner (TLS), based on Lidar technology, has demonstrated its potential to overcome the limitations of the conventional ground-based forest inventory techniques, but the accuracy and applicability of TLS techniques for estimation of tree attributes and canopy characterization, presupposes a correct separation between points representing shrubs, woody material, leaves and small branches and needs further investigations. In this work we developed and tested an automatic procedure based on the point density algorithms DBSCAN, to correctly separate points representing shrubs, woody material, leaves, and small branches at plot level, in order to identify woody material volumes, tree density and canopy cover on a forest stand. The study was carried out in several areas located in Sardinia, Italy, mainly covered by pine forest, mixed forest, and oak forest with different understory types. Destructive and non-destructive measurements were done inside circular plots of 10 m radius. TLS data sets were collected in field by multiple scanning of the plots. The 3D point clouds were processed for isolating trees, ground and understory and subsequently for separating wood from foliage. Cloud points were partitioned in cubic volumes (voxels) that were used as input to separate stand components (by applying principal component analysis) and to generate wood and no-wood clusters (by applying the point density algorithm DBSCAN). The first results obtained show that the proposed method allows to correctly identify foliage, trunk and main branches especially when the underlying layer is dominated by low herbaceous vegetation. However, further studies are needed to assess the ability of this method in forest stands characterized by high and dense undergrowth and with different species of trees.
The Impact of Terrain and Fire Duration on Boreal Fires in the LPJmL-SPITFIRE Fire-Enabled Dynamic Global Vegetation Model
Authors: Oberhagemann Luke , Drüke Markus , Bloh Werner von , Billing Maik , Sakschewski Boris , Rust Henning , Thonicke Kirsten
Published: October 2022

Fire-enabled Dynamic Global Vegetation Models (DGVMs) are used to model fire-vegetation interactions and their impacts on global vegetation dynamics. The challenge of modelling fires in boreal zones has been addressed by several DGVMs by allowing for longer modelled fire durations. However, DGVMs generally do not account for the impact of slope on increasing fire spread and only a few account for terrain-related landscape fragmentation. We investigate improvements to modelling boreal fires in the LPJmL-SPITFIRE DGVM by accounting for the impacts of terrain and incorporating longer fire durations. Our work is conducted in two parts: first, we investigate the impact of slope and terrain ruggedness on burnt area at the 0.5Â° by 0.5Â° resolution typical of DGVMs using satellite data, and with a particular focus on boreal regions. We demonstrate that terrain fragmentation acts as a limit on burnt area for the largest fires in a grid cell and that slope-driven wildfire spread can increase burnt area up to this limit. Therefore, these terrain effects are important for inclusion in fire modelling in general, and in boreal regions in particular. The second part of our work consists of the development of a function based on these results for implementation in LPJmL SPITFIRE and the evaluation of model improvements in boreal regions when this function is combined with longer fire durations. The results of this work represent a useful addition to LPJmL-SPITFIRE as well as DGVMs in general that do not incorporate the effects of terrain-based landscape fragmentation and slope-driven wildfire spread.
Vegetation Mapping with Random Forest using Sentinel 2- A case study for Lousã region, Portugal
Authors: Mohammadpour Pegah , Isbaex Crismeire , Chuvieco Emilio , Viegas Domingos Xavier , Viegas Carlos
Published: October 2022

Vegetation mapping requires accurate information to allow its use in applications such as sustainable forest management against the effects of climate change and the threat of wildfires. Remote sensing provides a powerful resource of fundamental data at different spatial resolutions and spectral regions, making it an essential tool for vegetation mapping and biomass management. Due to the ever-increasing availability of free data and software, satellites have been predominantly used to map, analyze, and monitor natural resources for conservation purposes. This study aimed to map vegetation from Sentinel-2 (S2) data in a complex and mixed vegetation cover of the Lousa district in Portugal. We used 10 multispectral bands with a spatial resolution of 10m, four vegetation indices including Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), Enhanced Vegetation Index (EVI), and Soil Adjusted Vegetation Index (SAVI). After applying Principal Component Analysis (PCA) on the 10 S2A bands, four texture features including Mean (ME), Homogeneity (HO), Correlation (COR), and Entropy (EN)were derived for the first three Principal Components. After defining the land use classes by object-based, the Random Forest (RF) classifier was applied. The map accuracy will be evaluated by the confusion matrix, using the metrics of Overall Accuracy (OA), Producer Accuracy (PA), User Accuracy (UA), and Kappa Coefficient (K). The described classification methodology is expected to show a high overall accuracy for vegetation mapping.
A comparison of two methods to measure pyrolysis gases in a wind tunnel and in prescribed burns
Authors: Weise David R. , Johnson Timothy J. , Myers Tanya L. , Hao Wei Min , Baker Stephen , Palarea-Albaladejo Javier
Published: October 2022

Pyrolysis products from wildland fuels are typically measured under tightly controlled conditions using fuels which have been processed to remove water content and physical shape. Different instruments can be used to identify and quantify the composition of these gases. Measurement of pyrolysis gases under conditions typical of wildland fires has seldom occurred. We used FTIR spectroscopy and GC/FID analysis to measure pyrolysis gases produced in wind tunnel experiments and small prescribed burns in longleaf pine needle fuel beds with live shrubs. Use of compositional data techniques on the 8 common gases measured by both methods showed that the compositions were affected by the measurement method and interaction between method and location was significant.
A Study of FDS Computational Performance in Heterogeneous Hardware Architectures -Applied for grassland fires
Authors: Kim Donghyun , Shin Jae-Ryul , Jeong Hwang-Hui
Published: October 2022

Fire Dynamic Simulator (FDS), a fire simulation program, applies Message Passing Interface (MPI) and Open Multi Processing (OpenMP) libraries for large-scale simulation. FDS can be executed by dividing simulation problems in a computing cluster using MPI. The main point is to divide the entire domain to be interpreted into several sub-domains and allow each sub-domain to be calculated by an individual computer with an individual processor. When performing parallel computation, FDS first decomposes each sub-domain, then supports two-step parallelization in which multi-threading is applied within each sub-domain, and uses the OpenMP library to implement multi-threading. In this study, OpenACC, a parallelization technique capable of using heterogeneous hardware architectures, was partially applied to FDS. As an application problem, the calculation performance is evaluated through CSIRO Grassland Fires, a verification case of FDS. The hardware for evaluation was a personal computer consisting of dual Xeon 2678-V3 and GeForce GTX 1070. The FDS source code applies OpenACC using PGI Fortran as a compiler in Linux environments. In calculation performance, calculations using CPU and GPU together show 1.89 times faster performance than calculations using a single CPU. In case of using 1 GPU and 16 CPUs (MPP + OpenACC), the analysis result is 21 times faster. In this regard, analysis of grassland fire of WFDS was performed.
A Study of the Ignition Mechanism for Dead Pinus Palustris Needles
Authors: Gong Weixuan , Cuevas Juan , Simeoni Albert
Published: October 2022

Combinations of cumulative impacts of drought, invasive species, climate variability, and ever-expanding wildland-urban interface make landscapes more susceptible to devastating wildland fires. To treat the increasing risks of wildland fires, one of the ways is to mitigate the risk of ignition, which requires a solid understanding of the ignition mechanism of vegetation fuels. This can be achieved mainly through discerning the degradation stage and the ignition criteria. Scaling up the experiments for the degradation stage and evaluating the suitability of existing ignition criteria are two of the primary challenges for ignition studies on vegetation fuels. Motivated by the challenges, two series of experiments were conducted using a modified Cone Calorimeter to understand the mechanisms driving the ignition of dead Pinus palustris needles. In the first set of experiments, the ignition of pine needles was studied for varied incident heat fluxes (20-35 kW/m2) and air flow rates (buoyancy-induced - 100 l/min forced flow). In the second set of experiments, Fourier transform infrared (FTIR) spectroscopy was used to characterize the composition of the pyrolysis gases generated from the thermal degradation of pine needles when exposed to various incident heat fluxes (20-35 kW/m2) under an inert atmosphere obtained using a flow of pure nitrogen (50-100 l/min). The results for the first series of experiments show that critical mass loss rate at ignition increase with both flow rates and heat flux, while the heat release rate at ignition was only influenced by the flow conditions. From the second set of experiments, it was found that methane (CH4), carbon monoxide (CO), carbon dioxide (CO2), and water vapor (H2O) are the main constituents of the pyrolysis gases. The predominance of these compounds was found to be independent of the external heat flux while their individual concentrations are sensitive to it. The flammability of pyrolysis gas was found to increase with external heat flux. The average content of flammable species, CH4 and CO, in the pyrolysis gas account for more than 31% at 20 kW/m2 and more than 40% at 30 kW/m2.
An Equivalent Fuel Model for Wildland Urban Interface – Application to Risk Management
Authors: Karzar-Jeddi Mehdi
Published: October 2022

Wildfires are imposing increasingly greater risk to people and insured properties. The frequency and intensity of destructive wildfires has increased significantly in past decades. Most wildfire damage to properties occurs in the wildland-urban interface (WUI), where properties are either exposed to wildfire directly and burn or are ignited by firebrands. Many wildfire models are focused on modelling the spread of fires in wildland; however, the studies of the spread of wildfires into urban areas is limited. This paper presents a new model for fuel load in urban area using an equivalent fuel load as wildland fuel to simulate wildfire spread when they approach wildland and urban interface/intermix. The model is to estimate the heat release rate from a typical single house and determine the combination of different fuel sizes. Then, according to the density of structures based on satellite imagery the fuel from LANDFIRE fuel is updated with the model urban fuel. A similar method of equivalent fuel load for agriculture area is developed and the LANDFIRE fuel is updated with the agriculture fuel. Using the updated landscape fuel and terrain, Rothermel-based simulation of wildfire is performed in FARSITE. This simulation is helpful in determining the risk of wildfires for properties and communities.