WHiLD-HM: A 4-km long-term (1952–2025) daily hydrometeorological dataset for the western United States

Harvard Dataverse · 2026-05-13

This dataset presents WHiLD-HM (Western U.S. High-resolution Long-term Dataset for Hydrometeorology), a 4-km spatial resolution, 74-year (1952–2025) daily hydrometeorological dataset for the western United States. The dataset is generated by forcing the Noah-MP land surface model (version 5) with high-quality observed meteorological data. It provides comprehensive spatiotemporal coverage of key hydrometeorological variables, including surface energy and water fluxes, soil moisture, snow water equivalent, and evapotranspiration components. The dataset demonstrates strong temporal and spatial agreement when evaluated against multiple observational datasets, including GLEAM, FLUXCOM, SMAP, and SNODAS. Cross-comparisons and case studies illustrate its ability to capture long-term drying trends, extreme drought and pluvial conditions, and hydroclimatic variability across multiple timescales. Notably, WHiLD-HM extends beyond the satellite era, enabling detailed analyses of daily-to-multidecadal hydroclimatic variability and extremes, and providing valuable information for water resource and food security management, ecohydrological monitoring, and climate change impact assessments in one of the most water-stressed and ecologically sensitive regions of the United States.

A fire deficit persists across diverse North American forests despite recent increases in area burned

Nature Communications · 2025-02-10 · 52 citations

Rapid increases in wildfire area burned across North American forests pose novel challenges for managers and society. Increasing area burned raises questions about whether, and to what degree, contemporary fire regimes (1984–2022) are still departed from historical fire regimes (pre-1880). We use the North American tree-ring fire-scar network (NAFSN), a multi-century record comprising >1800 fire-scar sites spanning diverse forest types, and contemporary fire perimeters to ask whether there is a contemporary fire surplus or fire deficit, and whether recent fire years are unprecedented relative to historical fire regimes. Our results indicate, despite increasing area burned in recent decades, that a widespread fire deficit persists across a range of forest types and recent years with exceptionally high area burned are not unprecedented when considering the multi-century perspective offered by fire-scarred trees. For example, ‘record’ contemporary fire years such as 2020 burned 6% of NAFSN sites—the historical average—well below the historical maximum of 29% sites that burned in 1748. Although contemporary fire extent is not unprecedented across many North American forests, there is abundant evidence that unprecedented contemporary fire severity is driving forest loss in many ecosystems and adversely impacting human lives, infrastructure, and water supplies. Across many North American forests, recent years with exceptional area burned are not unprecedented when considering the multi-century perspective offered by fire-scarred trees. Nevertheless, abundant evidence suggests that the severity of contemporary wildfire is unprecedented in its adverse impacts on forests and humans.

Supplementary material to "The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a)"

2025-07-29

Figure S1.Annual ignition locations of WUMI2024a wildfires with perimeter data from MTBS, WFIGS, CalFire, USGS, or IAFPH, as well as fires lacking perimeter data and assumed circular.

Effects of Hot Versus Dry Vapor Pressure Deficit on Ecosystem Carbon and Water Fluxes

Journal of Geophysical Research Biogeosciences · 2025-01-01 · 8 citations

Abstract Vapor pressure deficit (VPD) has increased and will likely continue increasing, with wide‐ranging effects on ecosystems. Future VPD increases will largely be driven by warming, yet most experiments examining VPD effects on plants have done so by changing humidity. Here, we used meteorological data and carbon and water fluxes measured at 26 climatically‐diverse eddy covariance sites to quantify the extent to which VPD has been driven by variation in air temperature versus humidity. We fit generalized additive models (GAMs) at each site to quantify effects of hotter (and wetter) and cooler (and drier) versus typical VPD on ecosystem‐scale fluxes of carbon and water. We found that VPD has occurred under diverse combinations of temperature and humidity: >50% of a site's daytime growing season temperature range and >35% of its relative humidity range have often combined to define a particular VPD. We found moderate evidence that hotter versus drier VPD of the same magnitude differentially affect gross primary productivity (GPP), net ecosystem productivity (NEP), and latent heat flux (LE): Selected GPP and NEP GAMs at about half of sites and LE GAMs at about a third of sites included a VPD‐temperature interaction. The magnitude of the interaction varied, but was generally 29%–57% of the effect attributable solely to VPD. The direction of the interaction also varied, but hot VPD was commonly associated with higher carbon fluxes. These effects were not strongly modified by soil moisture. Overall, results emphasize the relevance of VPD‐temperature interactions at a critical time of rapid VPD increase.

Wildfires drive multi-year water quality degradation over the western United States

Communications Earth & Environment · 2025-06-23 · 5 citations

Abstract Wildfires can dramatically alter water quality, resulting in severe implications for human and freshwater systems. However, regional-scale assessments of these impacts are often limited by data scarcity. Here, we unify observations from 1984–2021 in 245 burned watersheds across the western United States, comparing post-fire signals to baseline levels from 293 unburned basins. Organic carbon and phosphorus exhibit significantly elevated levels ( p ≤ 0.05) in the first 1–5 years post-fire, while nitrogen and sediment show significant increases up to 8 years post-fire. During peak post-fire response years, average carbon, nitrogen, and phosphorus concentrations are 3–103 times pre-fire levels, and sediment 19–286 times pre-fire concentrations. Higher responses are linked with greater forested and developed areas, which respectively explain up to 31 and 33% of inter-basin response variability. Overall, this analysis provides strong evidence of multi-year water quality degradation following wildfires in the western United States and highlights the influence of basin and wildfire features. These insights may aid water managers in preparation efforts, increasing resilience of water systems to wildfire impacts.

Influence of Time‐Averaging of Climate Data on Estimates of Atmospheric Vapor Pressure Deficit and Inferred Relationships With Wildfire Area in the Western United States

Geophysical Research Letters · 2025-03-29 · 4 citations

Abstract Vapor pressure deficit (VPD) is a driver of evaporative demand and correlates strongly with wildfire extent in the western United States (WUS). Vapor pressure deficit is the difference between saturation vapor pressure ( e s ) and actual vapor pressure ( e a ). Because e s increases nonlinearly with temperature, calculations of time‐averaged VPD vary depending on the frequency of temperature measurements and how e a is calculated, potentially limiting our understanding of fire‐climate relationships. We calculate eight versions of monthly VPD across the WUS and assess their differences. Monthly VPDs calculated from daily data are 2%–6% higher, and more accurate, than when calculated from monthly data. Using daily maximum and minimum temperature, instead of mean, increases VPD by ∼20%, but can overestimate true values depending on how e a is calculated. These differences do not meaningfully impact correlations with annual wildfire area, however, suggesting our understanding of historical fire‐VPD relations is not very sensitive to how VPD is calculated.

Evaluating Fire Indices for Fire Ignition and Spread Risk in the Western United States

2025-11-12

Wildfires are complex events that are challenging to model. Researchers and land managers often rely on fire indices as a proxy of fire risk in operational forecasts and future projections. However, in the scientific literature, the choice of which fire index to use is often arbitrary and not tied to specific fire behaviors. Here, we provide a comprehensive evaluation of 15 hydroclimate variables and fire indices based on their ability to represent daily ignition probability and spread rate in the western United States. Hydroclimate variables like saturation vapor pressure (E_S) and vapor pressure deficit (VPD) perform the best and most consistently at representing fire ignition probability across regions and vegetation types. Water-budget-based indices like 1000-hour dead fuel moisture (FM1000) and the Keetch-Byram Drought Index (KBDI) are best at representing ignition probability in forests. In contrast, indices like the Hot-Dry-Windy index (HDW) best represent fire spread rates, especially for non-forest fires, while indices from the National Fire Danger Rating System are best for forest fire spread. Partitioning the skill of variables/indices into contributions from capturing seasonality and anomalies, ignitions are distributed based on the seasonal cycles, while seasonality and anomalies are comparably important for spread rate. We demonstrate that computational complexity does not always result in better fire variables/indices, and that distinct sets of variables/indices are needed to represent different aspects of fire behavior, emphasizing the importance of making careful and justifiable selections of fire variables/indices.

Recent Increases in Missouri River Streamflow Driven by Combined Effects of Climate Variability, Land‐Use Change, and Elevated CO₂

AGU Advances · 2025-03-12 · 3 citations

Abstract Missouri River streamflow increased substantially during the 20th century, with multiple large floods occurring since 1990. Using land surface models and water budget simulations, we examined the extent to which increased flow was driven by natural climate variability, anthropogenic climate trends, land‐use and land‐cover change (LULCC), and ecological effects of elevated atmospheric CO 2 . Natural climate variability (arising largely from coupled ocean‐atmosphere circulation systems in both the Pacific and North Atlantic) accounted for ∼765 m 3 s −1 of the ∼900 m 3 s −1 increase in flow since mid‐century, while anthropogenic climate trends negatively forced flow by increasing evapotranspiration more than precipitation. LULCC and elevated CO 2 further increased simulated mean streamflow by ∼550 and ∼70 m 3 s −1 , respectively, relative to pre‐Industrial conditions and ∼100 and ∼65 m 3 s −1 relative to mid‐20th century conditions. The LULCC effect was especially large in wet years, implying that current land cover is ill‐suited for buffering against extreme precipitation, likely in large part due to replacement of forest by cropland in the lower basin. Because increases in Missouri River flow over the past century were driven mostly by a recent (and likely transient) pluvial, our results suggest that flow in the basin could revert to a drier mean state when that pluvial ends, likely made worse by increased evaporative demand from anthropogenic warming.

Wildfires drive multi-year water quality degradation over the western U.S.

Zenodo (CERN European Organization for Nuclear Research) · 2025-05-22

Information on the 245 burned basins, 293 unburned basins, and 356 associated fires from across the U.S. West which were used in statistical analyses of post-wildfire water quality response. Included are physiographic characteristics, as well as ESRI Shapefile polygons representing delineations for each basin and fire. Additionally, daily carbon, nitrogen, phosphorus, sediment, and turbidity data sampled from the basins' outlets are provided from 1974-2022. R coding scripts used in data processing and modeling also included, as well as data directly used in generating manuscript and "Supplementary Information" plots. Water quality data used to create this dataset are from the Water Quality Portal and wildfire burn perimeters are from the Monitoring Trends in Burn Severity database.

Megadroughts in the Common Era and the Anthropocene

UNC Libraries · 2025-04-17