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Variation of annual precipitation versus annual average fire size during 1984–2014. The vertical dashed lines associate the largest fires with annual precipitation
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Warming temperatures and severe droughts have contributed to increasing fire activity in California. Decadal average summer temperature in California has increased by 0.8 °C during 1984–2014, while the decadal total size of large fires has expanded by a factor of 2.5. This study proposes a multivariate probabilistic approach for quantifying changes...
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Citations
... However, the larger fires (> 1000 acres) are responsible for most of the dollar losses (> 90%) actually account for less than 0.2% of the total number of fires. Due to global warming the propensity of such wildfire incidents have been predicted to increase over time (Singo et al. 2023;Madadgar et al. 2020). ...
The frequency and the magnitude of the environmental hazards are going to be impacted by the changing climate. The non-stationary hazards can be effectively modelled using a Non-Homogeneous Poisson process (NHPP) with time-dependent rates and damages/losses associated with each hazard event. For risk analysis over a finite time, the compounded version of this process can give the net damages/losses with or without discounting. Panjer’s recursion mainly applicable to the Homogeneous Poisson process (HPP) can be slightly generalized to obtain the distribution of the net losses for an NHPP as well, that can only accommodate the time-dependent rates but there is no way to account for time-dependent losses or discounted losses for that matter. To address this limitation, this paper proposes a method to estimate the mean, variance and other higher-order moments of the compound NHPP under the most generalized condition i.e., both the rate and the losses, being time-dependent. This estimation is achieved by developing simple differential equations from the definition of the process, which can be solved easily using any suitable differential equation solver and the formulations are validated using Monte Carlo Simulations. This analysis can prove to be useful for estimating the risk in non-stationary climatic conditions and help provide a strong economic basis for investment decisions pertaining to climate action.
... This is likely due to the considerable regional variation exhibited by drivers of fire activity (Mees and Chase 1991;Stavros et al. 2014). For example, in southern California it was found that simple weather parameters such as temperature, relative humidity and wind alone were better predictors of fire size than more complex burn indices (Schoenberg et al. 2007;Madadgar et al. 2020). Furthermore, linear models demonstrate that autumn precipitation is significantly tied to the number of autumn fires, but the prior year spring precipitation is a better predictor of area burned (Keeley 2004). ...
Background Autumn and winter Santa Ana Winds (SAW) are responsible for the largest and most destructive wildfires in southern California. Aims (1) To contrast fires ignited on SAW days vs non-SAW days, (2) evaluate the predictive ability of the Canadian Fire Weather Index (CFWI) for these two fire types, and (3) determine climate and weather factors responsible for the largest wildfires. Methods CAL FIRE (California Department of Forestry and Fire Protection) FRAP (Fire and Resource Assessment Program) fire data were coupled with hourly climate data from four stations, and with regional indices of SAW wind speed, and with seasonal drought data from the Palmer Drought Severity Index. Key results Fires on non-SAW days were more numerous and burned more area, and were substantial from May to October. CFWI indices were tied to fire occurrence and size for both non-SAW and SAW days, and in the days following ignition. Multiple regression models for months with the greatest area burned explained up to a quarter of variation in area burned. Conclusions The drivers of fire size differ between non-SAW and SAW fires. The best predictor of fire size for non-SAW fires was drought during the prior 5 years, followed by a current year vapour pressure deficit. For SAW fires, wind speed followed by drought were most important.
... Fire weather is also a function of other prevailing meteorological conditions, such as wind speed and direction and lightning activity [31]. The complex interaction of these conditions with topographic features can either suppress or enhance the potential for wildfire ignition and spread [32][33][34][35]. Elevated land-based temperatures combined with low relative humidity (RH) imply drier air [2]. ...
California has experienced a surge in wildfires, prompting research into contributing factors, including weather and climate conditions. This study investigates the complex, multiscale interactions between large-scale climate patterns, such as the Boreal Summer Intraseasonal Oscillation (BSISO), El Niño Southern Oscillation (ENSO), and the Pacific Decadal Oscillation (PDO) and their influence on moisture and temperature fluctuations, and wildfire dynamics in California. The combined impacts of PDO and BSISO on intraseasonal fire weather changes; the interplay between fire weather index (FWI), relative humidity, vapor pressure deficit (VPD), and temperature in assessing wildfire risks; and geographical variations in the relationship between the FWI and climatic factors within California are examined. The study employs a multi-pronged approach, analyzing wildfire frequency and burned areas alongside climate patterns and atmospheric conditions. The findings reveal significant variability in wildfire activity across different climate conditions, with heightened risks during specific BSISO phases, La-Niña, and cool PDO. The influence of BSISO varies depending on its interaction with PDO. Temperature, relative humidity, and VPD show strong predictive significance for wildfire risks, with significant relationships between FWI and temperature in elevated regions (correlation, r > 0.7, p ≤ 0.05) and FWI and relative humidity along the Sierra Nevada Mountains (r ≤ −0.7, p ≤ 0.05).
... It is important to note, in this pilot study we are investigating risk for vulnerable populations in relation to the potential for negative consequences resulting from PSPS apart from losses or impacts from wildfires per se. Risk of exposure to wildfires [45,53] in the western U.S. is well studied, and vulnerable populations typically exhibit a concentration of vulnerable sociodemographic characteristics when compared to the population at large. Because PSPS zones are defined largely based on the potential for large wind-driven wildfires, those findings cannot be totally decoupled from ours. ...
Extreme events such as wildfires and winter storms result in disruptions to grid-based electricity delivery.Electricity supply disruptions are both reactive, whereby specific events cause damage to physical infrastructure,or anticipatory where electricity suppliers—namely electric utility companies—preemptively de-energize sections of an electrical grid or distribution network based on elevated potential of extreme conditions that may cause wildfire ignition. De-energization has been promoted as a strategy to mitigate risk of wildfire ignition and spread when active fires may encounter distribution/transmission lines. Provision of basic energy services such as electricity are necessary for maintaining a range of essential functions such as communication, which become critical during extreme events. In recent years, Public Safety Power Shutoffs (PSPS) have increasingly been deployed by utility companies in Western U.S states as wildfire risk increases due to combined impacts of anthropogenic climate change, fuel accumulation, and expansion of development in fire prone lands. While thePSPS policy was designed to reduce liability of utilities in igniting fires, there is a dearth of research critically analyzing how the policy affects social vulnerability for populations subjected to periods of de-energization during high-risk fire conditions. This article aims to deepen current understandings of the way scale can be deployed to illustrate the highly spatial nature of relationships coupling electricity supply outages with demographic data to advance limited knowledge on social vulnerability characteristics for specific communities subjected to PSPS. The research engages scale to compare social vulnerability to outages experienced both in Butte County, located in northern California and the state as a whole.
... Fire weather is also a function of other prevailing meteorological conditions, such as wind speed and direction, and lightning activity [31]. The complex interaction of these conditions with the topographic features can either suppress or enhance the potential for wildfire ignition and spread [32][33][34][35]. Elevated land-based temperatures combined with low relative humidity (RH) imply drier air [2]. ...
California has experienced a surge in wildfires, prompting research into contributing factors, including weather and climate conditions. This study investigates the complex, multiscale interactions between large-scale climate patterns, such as the Boreal Summer Intraseasonal Oscillation (BSISO), El Niño Southern Oscillation (ENSO), and the Pacific Decadal Oscillation (PDO), and their influence on moisture and temperature fluctuations, and wildfire dynamics in California. The combined impacts of PDO and BSISO on intraseasonal fire weather changes, the interplay between Fire Weather Index (FWI), relative humidity, vapor pressure deficit (VPD), and temperature in assessing wildfire risks, and geographical variations in the relationship between FWI and climatic factors within California are examined. The study employs a multi-pronged approach, analyzing wildfire frequency and burned areas alongside climate patterns and atmospheric conditions. Findings reveal significant variability in wildfire activity across different climate conditions, with heightened risks during specific BSISO phases, La-Niña, and cool PDO. The influence of BSISO varies depending on its interaction with PDO. Temperature, relative humidity, and VPD show strong predictive significance for wildfire risks, with significant relationships between FWI and temperature in elevated regions (correlation, r > 0.7, p ≤ 0.05) and FWI and relative humidity along the Sierra Nevada Mountains (r ≤ -0.7, p ≤ 0.05).
... Climate is commonly considered a determining factor in the size of fires, and historically, drought has been a significant factor (Madadgar et al.,2020;Ruffault et al.,2018). The effects of fires on forests are exacerbated by drought (Brando et al.,2014), leading to long-term changes in forest structure and biomass. ...
Forest fires have been a major concern for many countries over an extended period of time due to natural and human induced factors. In recent years, detection of forest fires has progressively shifted toward advanced technologies where the remote sensing approaches are fully operational. To enhance fire management strategies, it is crucial to gain a comprehensive understanding of the fire dynamics and its consequences on the environment, operational sources, and economic sectors. Therefore, this chapter develops an integrated framework to predict and analyze the effects of forest fires by using system dynamics approach and remote sensing technology, ultimately leading to the establishment of a conceptual model and conclusive insights.
... An increase in the temperature causes the quick drying of wildland fuel, and the drier fuels are easy to ignite and endure a faster rate of fire spread. Finally, Madadgar et al. [84] asserted that increased temperatures in the summer significantly influence forest vegetation flammability. ...
... Madadgar et al. [84] Temperature Increased temperature increased the vegetation's flammability. ...
Wildfire causes environmental, economic, and human problems or losses. This study reviewed wildfires induced by lightning strikes. This review focuses on the investigations of lightning mechanisms in the laboratory. Also, the paper aims to discuss some of the modeling studies on lightning-induced wildfires at different geographical locations using satellite-recorded lightning data and different statistical analyses. This review established that irrespective of the different models used to predict lightning wildfires, there is still a lack of understanding of the lightning-strike ignition mechanism; few experiments have been modeled to establish the dynamics of lightning-strike ignition. Therefore, further research needs to be carried out in this area to understand lightning ignition. It was ascertained from the various statistical modeling that lightning-induced wildfires are exacerbated by the abundant availability of fuel with a lower moisture content and high lightning efficiency. Moreover, because of changes in the climate and weather conditions, i.e., harsh weather and climate conditions due to anthropogenic activities, lightning-induced ignition wildfires have increased over the years, and they are expected to increase in the future if the climate and weather conditions continue to aggravate. Although various modeling studies have identified that lightning-induced wildfires have increased recently, no preventive measures have been conclusively proposed to reduce lightning-caused wildfires. Hence, this aspect of research has to be given critical attention. This review presents information that gives a profound understanding of lightning-induced wildfires, especially factors that influence lightning wildfires, and the state-of-the-art research that has been completed to understand lightning-induced wildfires.
... Moreover, the occurrence of sequential or simultaneous extreme climate events, often designated compound events, can have more severe impacts, compared to isolated events [11,15]. In particular, compound drought and hot events have been identified as drivers of large fires, such as during the extremely severe bushfire season of 2019-2020 in Australia [16,17], in the Mediterranean basin [18][19][20], in California [21], and in Brazil [22] but are also related to increased yield losses [11,[23][24][25]. ...
The occurrence of compound drought and hot events has been shown to cause stronger socio-economic, environmental and health impacts than the isolated events. Moreover, the frequency of these compound events has increased unevenly throughout and is expected to keep increasing in several regions of the world. In this work, an assessment of compound drought and hot events in the summer months in Australia was made, using copula functions. Drought and hot conditions were identified by the Standardized Precipitation Evapotranspiration Index (SPEI) and the indices Number of Hot Days (NHD) and Number of Hot Nights (NHN) for the summer months, respectively. We analysed drought conditions in the current and the previous 1 to 3 months and the periods 1950-1978 and 1979-2020. The results show that the conditional probability of the occurrence of hot events given drought conditions is very high for the concurrent month in most of the study area, reaching 0.9 in some cases. Considering previous drought conditions, the higher probabilities are obtained in the southeastern region in December and in the north in February, but on most of the study area these values are higher than for the case of non-drought conditions, pointing to an effect of previous drought conditions on hot events of up to 3 months. Moreover, an increased frequency of compound drought and hot events from the first to the second period was identified in more than half of the study area for lags 1 and 2.We show that, although the conditional probabilities are mostly higher when computed with NHD, NHN is also affected by drought conditions, and should also be considered in this analysis, since nights can have a relieving contribution when impacts in health and wildfires are being analysed.
... Rising temperatures, increasingly hot and lengthy droughts, and land use changes have contributed to intensifying wildfire activity around the world (Abatzoglou & Williams, 2016;Donovan et al., 2023;Keeley, 2004;Littell et al., 2009;Madadgar et al., 2020;Miller et al., 2009;Turco et al., 2014;Westerling et al., 2006) with substantial repercussions on the natural and built environment (Moftakhari & AghaKouchak, 2019;Thompson et al., 2011) and human health (Bowman & Johnston, 2005). For instance, the average annual area burned in the United States in the 1990s was 3.3 million acres, which more than doubled between 2013 and 2022, reaching an annual average of 7.2 million acres (CRS, Congressional Research Services, 2022). ...
The frequency, severity, and spatial extent of destructive wildfires have increased in several regions globally over the past decades. While direct impacts from wildfires are devastating, the hazardous legacy of wildfires affects nearby communities long after the flames have been extinguished. Post‐wildfire soil conditions control the persistence, severity, and timing of cascading geohazards in burned landscapes. The interplay and feedback between geohazards and wildfire‐induced changes to soil properties, land cover conditions, and near‐surface and surface processes are still poorly understood. Here, we synthesize wildfire‐induced processes that can affect the critical attributes of burned soils and their conditioning of subsequent geohazards. More specifically, we discuss the state of knowledge pertaining to changes in mineralogical, hydraulic, mechanical, and thermal properties of soil due to wildfire with a focus on advances in the past decade. We identify how these changes in soil properties alter evapotranspiration, interception, sediment transport, infiltration, and runoff. We then link these alterations to the evolution of different geohazards, including dry raveling, erosion, rockfalls, landslides, debris flows, and land subsidence. Finally, we identify research gaps and future directions to advance knowledge on how wildfires control the evolution of various earth surface processes and geohazards over time.
... Many of the largest fires are driven by Santa Ana winds, and occur in the fall ). Several statistical studies have projected future increases in fire size and frequency in this region (Barbero et al. 2015;Madadgar et al. 2020;Brey et al. 2021;Brown et al. 2021;Gao et al. 2021), and it has experienced several large, high-consequence contemporary wildfires (Keeley et al. 2009;Nauslar et al. 2018;. ...
Background
Wildfire is a major contemporary socio-ecological issue facing the people and natural resources of Southern California, and the prospect that a warming climate could lead to a higher probability of fire in the future is cause for concern. However, connecting climate change to projected burn probability is complex. While most models generally show temperature increasing in the future, changes in humidity and precipitation are less certain, and these changes interact to generate projections of future climates that are sometimes, but not always, more conducive to wildfire. We ran FSim, a stochastic, high-resolution spatial (270 m) and temporal (daily) fire spread model, with projected Energy Release Component (ERC) derived from multiple global climate models (GCMs) under RCP8.5 climate change scenario to explore the impact of a range of future climate trajectories on simulated burn probability and to quantify the uncertainty arising from multiple GCMs.
Results
We observed considerable uncertainty in the future direction of change for burn probability. Future changes were more certain in the Southern Coast region of California, where 75% of simulations projected an increase in burn probability. In the Central Coast region, five out of eight GCM-based simulations projected increased burn probability. Less than 1% of the total burnable study area had unanimous agreement on the projected direction of change. Simulated changes in burn probability were directly correlated to annual projections of changes in ERC, but were also affected by the seasonality of ERC change, as well as interactions between humidity, precipitation, and temperature.
Conclusions
The observed variability offers insights into why, and under what climate conditions, burn probability may increase or decrease in the future. Our study is novel in its examination of a wide range of potential future burn probability projections for Southern California using a regional application of a high-resolution stochastic fire spread model, and the complexity that we demonstrated for Southern California suggests that simple correlations of increasing fire with increasing temperature are likely underestimating the range of plausible future fire scenarios.
