Research Database
Displaying 21 - 40 of 72
Probabilistic Forecasting of Lightning Strikes over the Continental USA and Alaska: Model Development and Verification
Year: 2024
Lightning is responsible for the most area annually burned by wildfires in the extratropical region of the Northern Hemisphere. Hence, predicting the occurrence of wildfires requires reliable forecasting of the chance of cloud-to-ground lightning strikes during storms. Here, we describe the development and verification of a probabilistic lightning-strike algorithm running on a uniform 20 km grid over the continental USA and Alaska. This is the first and only high-resolution lightning forecasting model for North America derived from 29-year-long data records. The algorithm consists of a large…
Publication Type: Journal Article
Future fire events are likely to be worse than climate projections indicate – these are some of the reasons why
Year: 2024
BackgroundClimate projections signal longer fire seasons and an increase in the number of dangerous fire weather days for much of the world including Australia.AimsHere we argue that heatwaves, dynamic fire–atmosphere interactions and increased fuel availability caused by drought will amplify potential fire behaviour well beyond projections based on calculations of afternoon forest fire danger derived from climate models.MethodsWe review meteorological dynamics contributing to enhanced fire behaviour during heatwaves, drawing on examples of…
Publication Type: Journal Article
Hydrological and Meteorological Controls on Large Wildfire Ignition and Burned Area in Northern California during 2017–2020
Year: 2023
This study examined the hydrological/meteorological controls on large wildfires > 10,000 acres (40.5 km2) during 2017–2020 in Northern California at spatial and temporal scales of the target wildfires’ occurrence or growth. This study used the following simple indices for analysis: Moisture Deficit Index (MDI) computed by dividing vapor pressure deficit by soil moisture, MDIWIND computed by multiplying MDI by horizontal wind speed, and MDIGUST computed by multiplying MDI by wind gust speed. The ignition location MDIWIND and MDIGUST showed larger values on the ignition date in fire-years…
Publication Type: Journal Article
Dry Live Fuels Increase the Likelihood of Lightning-Caused Fires
Year: 2023
Live fuel moisture content (LFMC) is a key determinant of landscape ignition potential, but quantitative estimates of its effects on wildfire are lacking. We present a causal inference framework to isolate the effect of LFMC from other drivers like fuel type, fuel amount, and meteorology. We show that in California when LFMC is below a critical flammability threshold, the likelihood of fires is 1.8 times as high statewide (2.25% vs. 1.27%) and 2.5 times as high in shrubs, compared to when LFMC is greater than the threshold. This risk ratio is >2 times when LFMC is 10% less than the…
Publication Type: Journal Article
Examining the influence of mid-tropospheric conditions and surface wind changes on extremely large fires and fire growth days
Year: 2023
Background: Previous work by the author and others has examined weather associated with growth of exceptionally large fires (‘Fires of Unusual Size’, or FOUS), looking at three of four factors associated with critical fire weather patterns: antecedent drying, high wind and low humidity. However, the authors did not examine atmospheric stability, the fourth factor. Aims: This study examined the relationships of mid-tropospheric stability and dryness used in the Haines Index, and changes in surface wind speed or direction, to growth of FOUS. Methods. Weather measures were paired with daily…
Publication Type: Journal Article
Landscape‑scale fuel treatment effectiveness: lessons learned from wildland fire case studies in forests of the western United States and Great Lakes region
Year: 2023
Background Maximizing the effectiveness of fuel treatments at landscape scales is a key research and management need given the inability to treat all areas at risk from wildfire. We synthesized information from case studies that documented the influence of fuel treatments on wildfire events. We used a systematic review to identify relevant case studies and extracted information through a series of targeted questions to summarize experiential knowledge of landscape fuel treatment effectiveness. Within a larger literature search, we identified 18 case study reports that included (1) manager…
Publication Type: Journal Article
Smoke-weather interaction affects extreme wildfires in diverse coastal regions
Year: 2023
Extreme wildfires threaten human lives, air quality, and ecosystems. Meteorology plays a vital role in wildfire behaviors, and the links between wildfires and climate have been widely studied. However, it is not fully clear how fire-weather feedback affects short-term wildfire variability, which undermines our ability to mitigate fire disasters. Here, we show the primacy of synoptic- scale feedback in driving extreme fires in Mediterranean and monsoon climate regimes in the West Coast of the United States and Southeastern Asia. We found that radiative effects of smoke aerosols can modify near…
Publication Type: Journal Article
Fire needs annual grasses more than annual grasses need fire
Year: 2023
Sagebrush ecosystems of western North America are experiencing widespread loss and degradation by invasive annual grasses. Positive feedbacks between fire and annual grasses are often invoked to explain the rapid pace of these changes, yet annual grasses also appear capable of achieving dominance among vegetation communities that have not burned for many decades. Using a dynamic, remotely-sensed vegetation dataset in tandem with remotely-sensed fire perimeter and burn severity datasets, we examine the role of fire in transitions to and persistence of annual grass dominance in the U.S. Great…
Publication Type: Journal Article
Lightning-Ignited Wildfires in the Western United States: Ignition Precipitation and Associated Environmental Conditions
Year: 2023
Cloud-to-ground lightning with minimal rainfall (“dry” lightning) is a major wildfire ignition source in the western United States (WUS). Although dry lightning is commonly defined as occurring with <2.5 mm of daily-accumulated precipitation, a rigorous quantification of precipitation amounts concurrent with lightning-ignited wildfires (LIWs) is lacking. We combine wildfire, lightning and precipitation data sets to quantify these ignition precipitation amounts across ecoprovinces of the WUS. The median precipitation for all LIWs is 2.8 mm but varies with vegetation and fire characteristics…
Publication Type: Journal Article
Summer and Fall Extreme Fire Weather Projected to Occur More Often and Affect a Growing Portion of California throughout the 21st Century
Year: 2022
Annual burned area has increased in California over the past three decades as a result of rising temperatures and a greater atmospheric demand for moisture, a trend that is projected to continue throughout the 21st century as a result of climate change. Here, we implement a bias-correction and statistical downscaling technique to obtain high resolution, daily meteorological conditions for input into two fire weather indices: vapor pressure deficit (VPD) and the Canadian Fire Weather Index System (FWI). We focus our analysis on 10 ecoregions that together account for the diverse range of…
Publication Type: Journal Article
Extreme Winds Alter Influence of Fuels and Topography on Megafire Burn Severity in Seasonal Temperate Rainforests under Record Fuel Aridity
Year: 2022
Nearly 0.8 million hectares of land were burned in the North American Pacific Northwest (PNW) over two weeks under record-breaking fuel aridity and winds during the extraordinary 2020 fire season, representing a rare example of megafires in forests west of the Cascade Mountains. We quantified the relative influence of weather, vegetation, and topography on patterns of high burn severity (>75% tree mortality) among five synchronous megafires in the western Cascade Mountains. Despite the conventional wisdom in climate-limited fire regimes that regional drivers (e.g., extreme aridity, and…
Publication Type: Journal Article
Episodic occurrence of favourable weather constrains recovery of a cold desert shrubland after fire
Year: 2021
1. Key to the long-term resilience of dryland ecosystems is the recovery of foundation plant species following disturbance. In ecosystems with high interannual weather variability, understanding the influence of short-term environmental conditions on establishment of foundation species is essential for identifying vulnerable landscapes and developing restoration strategies. We asked how annual environmental conditions affect post-fire establishment of Artemisia tridentata, a shrub species that dominates landscapes across much of the western United States, and evaluated the influence of…
Publication Type: Journal Article
Existing Improvements in Simulation of Fire–Wind Interaction and Its Effects on Structures
Year: 2021
This work provides a detailed overview of existing investigations into the fire–wind interaction phenomena. Specifically, it considers: the fanning effect of wind, wind direction and slope angle, and the impact of wind on fire modelling, and the relevant analysis (numerical and experimental) techniques are evaluated. Recently, the impact of fire on buildings has been widely analysed. Most studies paid attention to fire damage evaluation of structures as well as structure fire safety engineering, while the disturbance interactions that influence structures have been neglected in prior studies…
Publication Type: Journal Article
Contrasting the role of human- and lightning-caused wildfires on future fire regimes on a Central Oregon landscape
Year: 2021
Climate change is expected to increase fire activity in many regions of the globe, but the relative role of human vs. lightning-caused ignitions on future fire regimes is unclear. We developed statistical models that account for the spatiotemporal ignition patterns by cause in the eastern slopes of the Cascades in Oregon, USA. Projected changes in energy release component from a suite of climate models were used with our model to quantify changes in frequency and extent of human and lightning-caused fires and record-breaking events based on sizes of individual fires between contemporary (2006…
Publication Type: Journal Article
Weather, Risk, and Resource Orders on Large Wildland Fires in the Western US
Year: 2020
Our results suggest that weather is a primary driver of resource orders over the course of extended attack efforts on large fires. Incident Management Teams (IMTs) synthesize information about weather, fuels, and order resources based on expected fire growth rather than simply reacting to observed fire growth. Background and Objectives: Weather conditions are a well-known determinant of fire behavior and are likely to become more erratic under climate change. Yet, there is little empirical evidence demonstrating how IMTs respond to observed or expected weather conditions. An understanding of…
Publication Type: Journal Article
Repeated fire altered succession and increased fire behavior in basin big sagebrush–native perennial grasslands
Year: 2020
The structure and composition of sagebrush-dominated ecosystems have been altered by changes in fire regimes, land use, invasive species, and climate change. This often decreases resilience to disturbance and degrades critical habitat for species of conservation concern. Basin big sagebrush (Artemisia tridentata ssp. tridentata) ecosystems, in particular, are greatly reduced in distribution as land has been converted to agriculture and other land uses. The fire regime, relative proportions of shrub and grassland patches, and the effects of repeated burns in this ecosystem are poorly understood…
Publication Type: Journal Article
Invasive grasses: A new perfect storm for forested ecosystems?
Year: 2020
Exotic grasses are a widespread set of invasive species that are notable for their ability to significantly alter key aspects of ecosystem function. Understanding the role and importance of these invaders in forested landscapes has been limited but is now rising, as grasses from Eurasia and Africa continue to spread through ecosystems of the Americas, Australia, and many Pacific islands, where they threaten biodiversity and alter various aspects of the fire regime. The ecological, social and economic impacts of the grass-fire cycle associated with species such as cheatgrass (Bromus tectorum)…
Publication Type: Journal Article
Severe Fire Danger Index: A Forecastable Metric to Inform Firefighter and Community Wildfire Risk Management
Year: 2019
Despite major advances in numerical weather prediction, few resources exist to forecast wildland fire danger conditions to support operational fire management decisions and community early-warning systems. Here we present the development and evaluation of a spatial fire danger index that can be used to assess historical events, forecast extreme fire danger, and communicate those conditions to both firefighters and the public. It uses two United States National Fire Danger Rating System indices that are related to fire intensity and spread potential. These indices are normalized, combined, and…
Publication Type: Journal Article
Not all Fuel-Reduction Treatments Degrade Biocrusts: Herbicides Cause Mostly Neutral to Positive Effects on Cover of Biocrusts
Year: 2019
In response to increasing fire, fuel-reduction treatments are being used to minimize large fire risk. Although biocrusts are associated with reduced cover of fire-promoting, invasive grasses, the impact of fuel-reduction treatments on biocrusts is poorly understood. We use data from a long-term experiment, the Sagebrush Steppe Treatment Evaluation Project, testing the following fuel-reduction treatments: mowing, prescribed fire, and the use of two herbicides: one commonly used to reduce shrub cover, tebuthiuron, and one commonly used to combat cheatgrass, imazapic. Looking at sites with high…
Publication Type: Journal Article
Long-Term Effects of Fire on Vegetation Structure and Predicted Fire Behavior in Wyoming Big Sagebrush Ecosystems
Year: 2018
Fire historically occurred across the sagebrush steppe, but little is known about how patterns of post-fire fuel accumulation influence future fire in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) communities. To quantify change in fuel composition and structure in intact sagebrush ecosystems, we sampled 17 years following prescribed fire in eight approximately 400 ha plots (4 burned, 4 unburned control) at Hart Mountain National Antelope Refuge, OR, USA. Fuels data were used to model potential fire behavior in burn and control plots across four environmental scenarios that…
Publication Type: Journal Article