Search Results (13)

Studies on estimating cumulative fire intensity from spreading wildland fires based on fire radiative energy density (FRED) have primarily been conducted through controlled experiments. The objective of this study was to assess the potential for estimating FRED for freely-burning wildfires at landscape scales. Airborne thermal infrared image sequences collected 8 and 9 December 2017 during the Thomas Fire were used for surface temperature derivation and FRED estimation. Sensitivity of varying ambient temperatures, and a newly developed method that adjusts for ash radiances on fire radiative flux density (FRFD) and FRED estimates were tested. Pixel-level image classification was run to identify FRFD time sequences that were complete or incomplete because of cloud obscuration and provided the basis for an obscuration gap filling technique. Variations in estimated ambient temperature used to estimate FRFD had little impact on FRED estimates, while our ash adjustment led to notable differences. An exponential decay model characterized FRFD time sequences well, providing a basis for gap filling irregular sequences caused by atmospheric obscuration. FRED estimates were regressed on rate of spread (ROS) magnitudes and found to be positively and significantly correlated. FRED magnitudes were higher on 9 December when the Thomas Fire burned under higher wind speeds and lower relative humidity levels (Santa Ana weather conditions) than on 8 December. Full article

Geovisualization tools can supplement the statistical analyses of landscape-level wildfire behavior by enabling the discovery of nuanced information regarding the relationships between fire spread, topography, fuels, and weather. The objectives of this study were to develop and evaluate the effectiveness of geovisualization tools for analyzing wildfire behavior and specifically to apply those tools to study portions of the Thomas and Detwiler wildfire events that occurred in California in 2017. Fire features such as active fire fronts and rate of spread (ROS) vectors derived from repetitive airborne thermal infrared (ATIR) imagery sequences were incorporated into geovisualization tools hosted in a web geographic information systems application. This geovisualization application included ATIR imagery, fire features derived from ATIR imagery (rate of spread vectors and fire front delineations), growth form maps derived from NAIP imagery, and enhanced topographic rasters for visualizing changes in local topography. These tools aided in visualizing and analyzing landscape-level wildfire behavior for study portions of the Thomas and Detwiler fires. The primary components or processes of fire behavior analyzed in this study were ROS, spotting, fire spread impedance, and fire spread over multidirectional slopes. Professionals and researchers specializing in wildfire-related topics provided feedback on the effectiveness and utility of the geovisualization tools. The geovisualization tools were generally effective for visualizing and analyzing (1) fire spread over multidirectional slopes; (2) differences in spread magnitudes within and between sequences over time; and (3) the relative contributions of fuels, slope, and weather at any given point within the sequences. Survey respondents found the tools to be moderately effective, with an average effectiveness score of 6.6 (n = 5) for the visualization tools on a scale of 1 (ineffective) to 10 (effective) for postfire spread analysis and visualizing fire spread over multidirectional slopes. The results of the descriptive analysis indicate that medium- and fine-scale topographic features, roads, and riparian fuels coincided with cases of fire spread impedance and exerted control over fire behavior. Major topographic features such as ridges and valleys slowed, or halted, fire spread consistently between study areas. The relationships between spotting, fuels, and topography were inconclusive. Full article

Wildfires have a strong influence on various geotechnical and hydraulic properties of soils and sediments, which may become more vulnerable to landslides or debris flows. In the present study, a case investigation of the 2018 post-wildfire debris flows in Montecito, California, USA, was conducted, with a focus on the wildfire-affected areas and debris volume estimation. Significant debris were deposited around four major creeks, i.e., Montecito Creek, San Ysidro Creek, Buena Vista Creek, and Romero Creek in January, 2018, one month after the Thomas fire. Satellite images utilizing remote sensing techniques and geographic information system (GIS) data were analyzed to identify areas affected by the wildfire. Relevant data, including the slope, catchment area, and rainfall were used in two empirical models to estimate the debris volumes around the four creeks. As compared with field observation, each debris volume estimated with these empirical models was within the same order of magnitude. The debris volumes were generally underestimated when using the rainfall recorded at the Montecito Weather Station; the estimates considerably improved with the rainfall record from the Doulton Tunnel Station. The results showed that, overall, such empirical approaches are still of benefit for engineering practice, as they are capable of offering first-order approximations. The accuracy and availability of rainfall data are critical factors; the rainfall data in mountainous areas are generally higher than in the low lands, and consequently were more suitable for debris volume estimation in the present study, where the debris flows typically occurred in areas with steep slopes and at higher elevations. Full article

Capacité de discernement, traitement de l’hypertension chez les personnes âgées et COVID long. Le Prof. Dr Andreas Schoenenberger de Münsterlingen s’est penché sur ces thèmes pertinents pour la pratique générale lors du 5e Congrès d’automne de la SSMIG «Medicine on Fire» à Interlaken. Tout à fait en accord avec le titre du congrès, les présentations des intervenants de cette année ont également porté sur les sujets brûlants de la médecine. La question d’actualité de la corticophobie, la dermatite atopique et le psoriasis, lorsque les atteintes ne se limitent pas à la peau – ces thèmes fréquents dans la pratique générale ont été abordés à la lumière des études récentes par le Prof. Dr Thomas Kündig (Zurich) dans sa présentation consacrée à la dermatologie. Full article

The objectives of this study were to evaluate spatial sampling and statistical aspects of landscape-level wildfire rate of spread (ROS) estimates derived from airborne thermal infrared imagery (ATIR). Wildfire progression maps and ROS estimates were derived from repetitive ATIR image sequences collected during the 2017 Thomas and Detwiler wildfire events in California. Three separate landscape sampling unit (LSU) sizes were used to extract remotely sensed environmental covariates known to influence fire behavior. Statistical relationships between fire spread rates and landscape covariates were analyzed using (1) bivariate regression, (2) multiple stepwise regression, (3) geographically weighted regression (GWR), (4) eigenvector spatial filtering (ESF) regression, (5) regression trees (RT), and (6) and random forest (RF) regression. GWR and ESF regressions reveal that relationships between covariates and ROS estimates are substantially non-stationary and suggest that the global association of fire spread controls are locally differentiated on landscape scales. Directional slope is by far the most strongly associated covariate of ROS for the imaging sequences analyzed and the size of LSUs has little influence on any of the covariate relationships. Full article

The objectives of this study are to evaluate landscape-scale fuel and terrain controls on fire rate of spread (ROS) estimates derived from repetitive airborne thermal infrared (ATIR) imagery sequences collected during the 2017 Thomas and Detwiler extreme wildfire events in California. Environmental covariate data were derived from prefire National Agriculture Imagery Program (NAIP) orthoimagery and USGS digital elevation models (DEMs). Active fronts and spread vectors of the expanding fires were delineated from ATIR imagery. Then, statistical relationships between fire spread rates and landscape covariates were analyzed using bivariate and multivariate regression. Directional slope is found to be the most statistically significant covariate with ROS for the five fire imagery sequences that were analyzed and its relationship with ROS is best characterized as an exponential growth function (adj. R² max = 0.548, min = 0.075). Imaged-derived fuel covariates alone are statistically weak predictors of ROS (adj. R² max = 0.363, min = 0.002) but, when included in multivariate models, increased ROS predictability and variance explanation (+14%) compared to models with directional slope alone. Full article

Understanding the mechanisms underlying tree spatial arrangements may provide significant insights into the processes in the maintenance of species coexistence. We examined the potential role of habitat heterogeneity, dispersal limitation, negative density dependence, fire history, and unilateral intraspecific and interspecific interactions of adults on juveniles in shaping the spatial patterns of four dominant tree species (Abies concolor, Pinus lambertiana, Calocedrus decurrens, and Quercus kelloggii) after fire in the Yosemite Forest Dynamic Plot, California, USA. We used the univariate pair correlation function and implemented three point pattern processes (homogeneous Poisson process, inhomogeneous Poisson process, and homogeneous Thomas process) to evaluate the potential contributions of habitat filtering and dispersal limitation. We used a bivariate null model to evaluate unilateral intraspecific and interspecific interactions of adults on juveniles. We also used the pairwise correlation function to investigate the spatial patterns of density dependence. To understand the effect of fire, we used the univariate pair correlation function to investigate pattern changes during the six years following fire. We compared spatial pattern changes in both sprouting species (Quercus kelloggii) and seeding species (Abies concolor), and also examined the changes in patterns of large-diameter individuals of Abies concolor, Pinus lambertiana, and Calocedrus decurrens in 2013 (pre-fire), 2016 (two years post-fire), and 2019. Comparing the contributions of the homogeneous Thomas process and the inhomogeneous Poisson process at different spatial scales showed the importance of dispersal limitation and habitat heterogeneity at finer scales (0 m to 5 m) and coarser scales (5 m to 60 m), respectively, which suggests that the joint effects of dispersal limitation and habitat heterogeneity contribute to the spatial patterns of these three dominant tree species. Furthermore, the results showed that the young individuals of Abies concolor and Pinus lambertiana were more commonly found around the conspecific adults. Juvenile regeneration to the 1 cm diameter threshold was highly aggregated following the fire. Large-diameter trees of Abies concolor, Pinus lambertiana, and Calocedrus decurrens generally did not exhibit patterns different from complete spatial randomness (Calocedrus decurrens), or displayed only slight aggregation (Abies concolor and Pinus lambertiana). In addition, Abies concolor and Pinus lambertiana showed positive and negative conspecific density dependence in the immediate post-fire period, respectively. Full article

Wildfire disasters are one of the many consequences of increasing wildfire activities globally, and much effort has been made to identify strategies and actions for reducing human vulnerability to wildfire. While many individual homeowners and communities have enacted such strategies, the number subjected to a subsequent wildfire is considerably lower. Furthermore, there has been limited documentation on how mitigation strategies impact wildfire outcomes across the socio-ecological spectrum. Here we present a case report documenting wildfire vulnerability mitigation strategies undertaken by the community of Montecito, California, and how such strategies addressed exposure, sensitivity, and adaptive capacity. We utilize geospatial data, recorded interviews, and program documentation to synthesize how those strategies subsequently impacted the advance of the 2017 Thomas Fire on the community of Montecito under extreme fire danger conditions. Despite the extreme wind conditions and interviewee estimates of potentially hundreds of homes being consumed, only seven primary residences were destroyed by the Thomas Fire, and firefighters indicated that pre-fire mitigation activities played a clear, central role in the outcomes observed. This supports prior findings that community partnerships between agencies and citizens are critical for identifying and implementing place-based solutions to reducing wildfire vulnerability. Full article

Debris flows in a burned area, post-fire debris flows, are considered as one of the most dangerous geo-hazards due to their high velocity, long run-out distance, and huge destruction to infrastructures. The rainfall threshold to trigger such hazards is often reduced compared with normal debris flow because ashes generated by mountain fires reduce the permeability of the top soil layer, thus increasing surface runoff. At the same time, burnt material and residual debris have very poor geo-mechanical characteristics, e.g., their internal friction angle and cohesion are typically low, and thus an intense rainfall can easily trigger some debris flows. Studying post-fire debris flow enables us to get a deeper understanding of disaster management. In this paper, the debris flow that occurred in Montecito, California, USA, and was affected by the Thomas Fire was used as a case study. Five major watersheds were extracted based on the digital elevation model (DEM). Remote sensing images were used to analyze the wildfire process, the extent of the burned areas, and the burn severity. The hypsometric integral (HI) and short-duration rainfall records of the watersheds around Montecito when the post-fire debris flows occurred were analyzed. Steep terrain, loose and abundant deposits, and sufficient water supply are the important conditions affecting the formation of debris flows. Taking watersheds as the research objects, HI was used to describe the geomorphic and topographic features, open-access rainfall data was used to represent the water supply, and burn severity represented the abundance of material sources. An occurrence probability model of post-fire debris flow based on HI, short-duration heavy rainfall, and burn severity was developed by using a logistic regression model in post-fire areas. By using this model, the occurrence probability of the post-fire debris flow in different watersheds around Montecito was analyzed based on the precipitation with time. Especially, the change characteristics of occurrence probability of debris flows over time based on the model bring a new perspective to observe the obvious change of the danger of post-fire debris flows and it is very useful for early warning of post-fire debris flows. Full article

We analyze observed and simulated winds and gusts occurring before, during, and immediately after the ignition of the Thomas fire of December 2017. This fire started in Ventura county during a record-long Santa Ana wind event from two closely located but independent ignitions and grew to become (briefly) the largest by area burned in modern California history. Observations placed wind gusts as high as 35 m/s within 40 km of the ignition sites, but stations much closer to them reported much lower speeds. Our analysis of these records indicate these low wind reports (especially from cooperative “CWOP” stations) are neither reliable nor representative of conditions at the fire origin sites. Model simulations verified against available better quality observations indicate downslope wind conditions existed that placed the fastest winds on the lee slope locations where the fires are suspected to have started. A crude gust estimate suggests winds as fast as 32 m/s occurred at the time of the first fire origin, with higher speeds attained later. Full article

Wildfires are a major hazard to humans in the southern California Mediterranean ecosystem and improving our understanding and delineation of different fire regimes is critical to mitigating wildfire-related hazards. Recent research has demonstrated that there are two distinct fire regimes in this region based on the presence or absence of katabatic winds (primarily Santa Ana winds) concurrent with the fire. Here, we expand the katabatic wind category to include Sundowner winds along the Santa Barbara front range and analyze the spatial relationships and difference in ignition sources between fires associated with katabatic and non-katabatic wind events from 1948–2017. We found distinct spatial extents for katabatic versus non-katabatic fires, with areas of the higher number of repeat fires generally associated with one fire type or the other. These spatial delineations were consistent with prior analyses of katabatic wind patterns and were also related to the climatology of marine influences across the region. Finally, we contextualize the burn perimeter of the 2017 Thomas Fire, the largest fire in modern California history, relative to spatial patterns of katabatic and non-katabatic fires. The 2017 Thomas Fire began during the longest Santa Ana event in the last 70 years in an area that has been burned repeatedly by Santa Ana fires. However, the Thomas Fire ultimately burned into a region where there were no prior Santa Ana fires. The spatial delineation of two relatively distinct fire regimes is critical to making management decisions, such as where to locate suppression resources at critical times and where fuel treatments might be most effective. However, the anomalous pattern of the Thomas Fire also points to the potential for changes in anthropogenic and environmental factors to disrupt historical spatial patterns and suggests that spatial patterns of fire regimes are themselves prospective metrics of global change. Full article

The physicians of the Alexandrine school seem to have been able to follow the way of the optic nerves from the retina to the brain. It was very probable that they should discover the thalamus. Sadly, anatomic knowledge, deriving from the first scientific human dissection performed in history, was destroyed in the fire of the Alexandrine Library. When, in the second century A.D., Galen introduced the term thalamus opticus, he was describing the central part of the lateral ventricles of the brain. After Galen, an anatomy with philosophical inferences substituted an anatomy based on direct observation. At that time the purpose was to find the site of the soul. During the thirteen centuries following Galen, including the Byzantine epoch and the High Middle Ages, the knowledge of the anatomy of the central nervous system did not make any substantial progress. The deep location of the thalamus contributed, for a very long time, to make it invisible to the eyes of the anatomists. It was Mondino da Luzzi, during the thirteenth century A.D., who gave the first incontestable description of the thalamus. He named the thalamus anchae (buttocks). Nevertheless, we should also consider the hypothesis that Galen, from whom Mondino always got his inspiration, could already have used the Latin term nates to name the pulvinar of the thalamus. Three centuries later,Andreas Vesalius, the true father of modern anatomy, first illustrated the thalamus in his artwork De humani corporis fabrica (1543). The thalamus was perfectly represented by Vesalio. He provided figures of the thalamus with accurate legends in many brain sections with different perspectives but, strangely, he did not mention it in the text. In the seventeenth century, Jean Riolan and Thomas Willis inaugurated the use of the term “thalamus” in its actual meaning, probably as a consequence of an inaccurate interpretation or the transcription of Galen’s writings. The thalamus has superbly been represented by Willis and Vieussens in their De Cerebri Anatome (1664) and Neuronographia Universalis (1684). These works were the first monographs of the human history to be integrally devoted to the central nervous system. During the eighteenth century the anatomic illustration began to conform itself more to a scientific than an artistic approach. Nevertheless, despite the presence of the thalamus in most atlases, only little scientific progress was made in its understanding. During that century,Alexander Monro (Monro Primus, 1697–1767) described the hypothalamic sulcus and the interventricular foramens clarifying their topography with the thalamic walls. Giovanni Domenico Santorini (1681–1737) accurately reported the link between the optic tracts and the structure he first named as the lateral geniculate body of the thalamus. François Pourfour du Petit (1664–1741), Santorini and then Félix Vicq d’Azyr (1748–1794) described the mammillothalamic tract. The physicians of the Alexandrine school seem to have been able to follow the way of the optic nerves from the retina to the brain. It was very probable that they should discover the thalamus. Sadly, anatomic knowledge, deriving from the first scientific human dissection performed in history, was destroyed in the fire of the Alexandrine Library. When, in the second century A.D., Galen introduced the term thalamus opticus, he was describing the central part of the lateral ventricles of the brain. After Galen, an anatomy with philosophical inferences substituted an anatomy based on direct observation. At that time the purpose was to find the site of the soul. During the thirteen centuries following Galen, including the Byzantine epoch and the High Middle Ages, the knowledge of the anatomy of the central nervous system did not make any substantial progress. The deep location of the thalamus contributed, for a very long time, to make it invisible to the eyes of the anatomists. It was Mondino da Luzzi, during the thirteenth century A.D., who gave the first incontestable description of the thalamus. He named the thalamus anchae (buttocks). Nevertheless, we should also consider the hypothesis that Galen, from whom Mondino always got his inspiration, could already have used the Latin term nates to name the pulvinar of the thalamus. Three centuries later,Andreas Vesalius, the true father of modern anatomy, first illustrated the thalamus in his artwork De humani corporis fabrica (1543). The thalamus was perfectly represented by Vesalio. He provided figures of the thalamus with accurate legends in many brain sections with different perspectives but, strangely, he did not mention it in the text. In the seventeenth century, Jean Riolan and Thomas Willis inaugurated the use of the term “thalamus” in its actual meaning, probably as a consequence of an inaccurate interpretation or the transcription of Galen’s writings. The thalamus has superbly been represented by Willis and Vieussens in their De Cerebri Anatome (1664) and Neuronographia Universalis (1684). These works were the first monographs of the human history to be integrally devoted to the central nervous system. During the eighteenth century the anatomic illustration began to conform itself more to a scientific than an artistic approach. Nevertheless, despite the presence of the thalamus in most atlases, only little scientific progress was made in its understanding. During that century,Alexander Monro (Monro Primus, 1697–1767) described the hypothalamic sulcus and the interventricular foramens clarifying their topography with the thalamic walls. Giovanni Domenico Santorini (1681–1737) accurately reported the link between the optic tracts and the structure he first named as the lateral geniculate body of the thalamus. François Pourfour du Petit (1664–1741), Santorini and then Félix Vicq d’Azyr (1748–1794) described the mammillothalamic tract. Full article