Drivers of California’s changing wildfires: a state-of-the-knowledge synthesis

International Journal of Wildland Fire, Journal Year: 2023, Volume and Issue: 32(7), P. 1039 - 1058

Published: May 22, 2023

Over the past four decades, annual area burned has increased significantly in California and across western USA. This trend reflects a confluence of intersecting factors that affect wildfire regimes. It is correlated with increasing temperatures atmospheric vapour pressure deficit. Anthropogenic climate change driver behind much this change, addition to influencing other climate-related factors, such as compression winter wet season. These climatic trends associated increases fire activity are projected continue into future. Additionally, related suppression Indigenous use fire, aggressive and, some cases, changes logging practices or fuel management intensity, collectively have produced large build-ups vegetative fuels ecosystems. Human activities provide most common ignition source for California’s wildfires. Despite its human toll, provides range ecological benefits many Given diversity vegetation types regimes found state, addressing challenges will require multi-faceted locally targeted responses terms management, human-caused ignitions, building regulations restrictions, integrative urban ecosystem planning, collaboration Tribes support reinvigoration traditional burning

Language: Английский

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Two Decades of Dust Radiative Forcing on Snow Cover Across the Great Salt Lake Basin

Journal of Geophysical Research Earth Surface, Journal Year: 2025, Volume and Issue: 130(2)

Published: Feb. 1, 2025

Abstract Seasonal snowpacks in mountain drainages of the Great Salt Lake Basin (GSLB), western United States, are primary surface water supply to regional agriculture, metropolitan Wasatch Front, and terminal Lake. Spring dust emissions from eastern result a dust‐darkened GSLB snowpack, locally accelerating snowmelt relative dust‐free conditions. Such acceleration has been linked streamflow forecasting errors adjacent Colorado River Basin, but snow darkening impacts within largely uninvestigated. To quantify impact, we analyzed patterns radiative forcing (RF ) over MODIS record (2001–2023) using spatially temporally complete RF fractional snow‐covered area products. For validation, retrievals were cross‐referenced with situ observations. Results showed that was present every year had no significant trend record. Spatially, similar across all three subbasins. Temporally, exhibited high interannual variability (−30 +40 Wm −2 means) declined slightly regions GSLB. Controls may be seasonal meteorology drought conditions, drivers remain uncertain. Further understanding distribution controls during changing climate weather allow us predict more accurately.

Language: Английский

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Characteristics of the spatiotemporal differences in snowmelt phenology in the Northern Hemisphere

Journal of Hydrology Regional Studies, Journal Year: 2025, Volume and Issue: 59, P. 102358 - 102358

Published: April 10, 2025

Language: Английский

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Declines in Peak Snow Water Equivalent and Elevated Snowmelt Rates Following the 2020 Cameron Peak Wildfire in Northern Colorado

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(6)

Published: March 28, 2023

Abstract Wildfires are increasingly impacting high‐elevation forests in the western United States that accumulate seasonal snowpacks, presenting a major disturbance to critical water reservoir for region. In first winter following 2020 Cameron Peak wildfire Colorado, peak snow equivalent high burn severity forest was 17%–25% less than nearby unburned sites. The loss of canopy and lower surface albedo led an positive net shortwave radiation balance burned area, resulting melt rates were 82%–144% greater sites disappearance occurred 11–13 days earlier. Late‐season storms temporarily buried soot, thus increasing delaying melt‐out by estimated 4 per storm our study area. While these reduce higher imposed impacts, SNOTEL measurements show they occur non‐uniformly across U.S.

Language: Английский

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Spatio-temporal patterns and trends in MODIS-retrieved radiative forcing by snow impurities over the Western US from 2001 to 2022

Environmental Research Climate, Journal Year: 2024, Volume and Issue: 3(2), P. 025001 - 025001

Published: Feb. 12, 2024

Abstract The seasonal mountain snowpack of the Western US (WUS) is a key water resource to millions people and an important component regional climate system. Impurities at snow surface can affect snowmelt timing rate through radiative forcing (RF), resulting in earlier streamflow, disappearance, less availability dry months. Predicting locations, timing, intensity impurities challenging, little known concerning whether RF has changed over recent decades. Here we analyzed relative magnitude spatio-temporal variability across WUS three spatial scales (pixel, watershed, regional) using remotely sensed from spatially temporally complete (STC) MODIS data sets (STC-MODIS Snow Covered Area Grain Size/MODIS Dust Radiative Forcing on Snow) 2001 2022. To quantify impacts, calculated pixel-integrated metric each season (1st March–30th June) all 22 years. We tested for long-term trend significance with Mann–Kendall test Theil–Sen’s slope. Mean was highest Upper Colorado region, but notable less-studied regions, including Great Basin Pacific Northwest. Watersheds high also tended have temporal RF, these be near arid regions. trends were largely absent; only small percent ecoregions (0.03%–8%) had significant trends, typically decreasing trends. All exhibited net decline RF. While extent minimal, found declining most frequently Sierra Nevada, North Cascades, Canadian Rockies, increasing Idaho Batholith. This study establishes two-decade chronology WUS, helping inform where when impacts may need considered hydrologic models hydroclimate studies.

Language: Английский

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Post-fire reference densities for giant sequoia seedlings in a new era of high-severity wildfires

Forest Ecology and Management, Journal Year: 2024, Volume and Issue: 562, P. 121916 - 121916

Published: April 26, 2024

Language: Английский

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Anticipating how rain-on-snow events will change through the 21st century: lessons from the 1997 new year’s flood event

Climate Dynamics, Journal Year: 2024, Volume and Issue: 62(9), P. 8615 - 8637

Published: Aug. 1, 2024

Abstract The California-Nevada 1997 New Year’s flood was an atmospheric river (AR)-driven rain-on-snow (RoS) event and remains the costliest in their history. joint occurrence of saturated soils, rainfall, snowmelt generated inundation throughout northern California-Nevada. Although AR RoS events are projected to occur more frequently with climate change, warming sensitivity drivers across scales understudied. We leverage regionally refined mesh capabilities Energy Exascale Earth System Model (RRM-E3SM) recreate horizontal grid spacings 3.5 km California, forecast lead times up 4 days, six levels ranging from pre-industrial conditions $$+3.5\,^\circ$$ + 3.5 ∘ C. describe including duration intensity, precipitation phase, intensity efficiency, snowpack mass energy changes, runoff efficiency. Our findings indicate current change negligibly influence drivers. At $$\ge 1.7\,^\circ$$ ≥ 1.7 C, hazard potential increases, nonlinearly decreases, antecedent soil moisture decreases (except where snowline retreats), southern Sierra Nevada persists). Storm total but at rates below warming-induced increases saturation-specific humidity. Warming intensifies short-duration, high-intensity particularly snowfall-to-rainfall transitions occur. This study highlights nonlinear tradeoffs 21st-century hazards provides water management infrastructure investment adaptation considerations.

Language: Английский

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Illuminating Snow Droughts: The Future of Western United States Snowpack in the SPEAR Large Ensemble

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(10)

Published: May 25, 2024

Abstract Seasonal snowpack in the Western United States (WUS) is vital for meeting summer hydrological demands, reducing intensity and frequency of wildfires, supporting snow‐tourism economies. While severity snow droughts (SD), that is, anomalously low snowpacks, are expected to increase under continued global warming, uncertainty from internal climate variability remains challenging quantify with observations alone. Using a 30‐member large ensemble state‐of‐the‐art model, Seamless System Prediction EArth Research (SPEAR), an observations‐based data set, we find WUS SD changes already significant. By 2100, SPEAR projects SDs be nearly 9 times more frequent shared socioeconomic pathway 5‐8.5 (SSP5‐8.5) 5 SSP2‐4.5, compared 1921–2011 average. investigating influence two primary drivers SD, temperature precipitation amount, average will become warmer wetter. To assess how these affect future water availability, track late winter spring across watersheds, finding differences onset time “no‐snow” threshold between regions within both on order decades. We attribute inter‐regional regions' mean intra‐regional irreducible which not well‐explained by variations Despite strong scenario forcing, continue drive no‐snow conditions through 2100.

Language: Английский

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The Severity of the 2014–2015 Snow Drought in the Oregon Cascades in a Multicentury Context

Water Resources Research, Journal Year: 2023, Volume and Issue: 59(5)

Published: May 1, 2023

Abstract The western United States (US) is a hotspot for snow drought. Oregon Cascade Range highly sensitive to warming and as result has experienced the largest mountain snowpack losses in US since mid‐20th century, including record‐breaking drought 2014–2015 that culminated state of emergency. While snowpacks serve state's primary water supply, short instrumental records limit managers' ability fully constrain long‐term natural variability prior influence ongoing projected anthropogenic climate change. Here, we use annually‐resolved tree‐ring develop first multi‐century reconstruction April 1st Snow Water Equivalent (SWE). model explains 58% observed extends back 1688 AD, nearly quintupling length existing record. Our suggests only one other multiyear event last three centuries was severe 2015 alone more than any year over centuries. Extreme low‐to‐high “whiplash” transitions are consistent feature throughout reconstructed Multi‐decadal intervals persistent below‐the‐mean peak SWE prominent features pre‐instrumental variability, but generally absent from period likely not accounted modern management. In face intensification warming, our findings motivate adaptive management strategies address declining increasingly variable precipitation regimes.

Language: Английский

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Subseasonal Prediction of Impactful California Winter Weather in a Hybrid Dynamical‐Statistical Framework

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(23)

Published: Nov. 30, 2023

Abstract Atmospheric rivers (ARs) and Santa Ana winds (SAWs) are impactful weather events for California communities. Emergency planning efforts resource management would benefit from extending lead times of skillful prediction these other types extreme patterns. Here we describe a methodology subseasonal winter in California, including ARs, SAWs heat extremes. The hybrid approach combines dynamical model historical information to forecast probabilities outcomes at weeks 1–4 lead. This uses considered most reliable, that is, planetary/synoptic‐scale atmospheric circulation, filters error/uncertainty longer increases the sample likely by utilizing full record instead more limited suite ensemble members. We demonstrate skill above climatology timescales, highlighting potential use water, health, land, fire decision support.

Language: Английский

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