Accounting for among-sampler variability improves confidence in fuel moisture content field measurements

Background: Direct fuel moisture content measurements are critical for characterising spatio-temporal variations in fuel flammability and for informing fire danger assessments. However, among-sampler variability (systematic differences in measurements between samplers) likely contributes to fuel moisture measurement variability in most field campaigns. Aims: We assessed the magnitude of among-sampler variability in plot-scale Calluna vulgaris fuel moisture measurements. Methods: Seventeen individuals collected samples from six fuel layers hourly from 10:00 hours to 18:00 hours. We developed mixed effects models to estimate the among-sampler variability. Key results: Fuel moisture measurements were highly variable between individuals sampling within the same plot, fuel layer, and time of day. The importance of among-sampler variability in explaining total measured fuel moisture variance was fuel layer dependent. Among-sampler variability explained the greatest amount of measurement variation in litter (58%) and moss (45%) and was more important for live (19%) than dead (4%) Calluna. Conclusions: Both consideration of samplers within the experimental design and incorporation of sampler metadata during statistical analysis will improve understanding of spatio-temporal fuel moisture dynamics obtained from field-based studies. Implications: Accounting for among-sampler variability in fuel moisture campaigns opens opportunities to utilise sampling teams and citizen science research to examine fuel moisture dynamics over large spatio-temporal scales.</p

Landscape controls on fuel moisture variability in fire-prone heathland and peatland landscapes

Background: Cross-landscape fuel moisture content is highly variable but not considered in existing fire danger assessments. Capturing fuel moisture complexity and its associated controls is critical for understanding wildfire behavior and danger in emerging fire-prone environments that are influenced by local heterogeneity. This is particularly true for temperate heathland and peatland landscapes that exhibit spatial differences in the vulnerability of their globally important carbon stores to wildfire. Here we quantified the range of variability in the live and dead fuel moisture of Calluna vulgaris across a temperate fire-prone landscape through an intensive fuel moisture sampling campaign conducted in the North Yorkshire Moors, UK. We also evaluated the landscape (soil texture, canopy age, aspect, and slope) and micrometeorological (temperature, relative humidity, vapor pressure deficit, and windspeed) drivers of landscape fuel moisture variability for temperate heathlands and peatlands for the first time. Results: We observed high cross-landscape fuel moisture variation, which created a spatial discontinuity in the availability of live fuels for wildfire spread (fuel moisture &lt; 65%) and vulnerability of the organic layer to smoldering combustion (fuel moisture &lt; 250%). This heterogeneity was most important in spring, which is also the peak wildfire season in these temperate ecosystems. Landscape and micrometeorological factors explained up to 72% of spatial fuel moisture variation and were season- and fuel-layer-dependent. Landscape factors predominantly controlled spatial fuel moisture content beyond modifying local micrometeorology. Accounting for direct landscape–fuel moisture relationships could improve fuel moisture estimates, as existing estimates derived solely from micrometeorological observations will exclude the underlying influence of landscape characteristics. We hypothesize that differences in soil texture, canopy age, and aspect play important roles across the fuel layers examined, with the main differences in processes arising between live, dead, and surface/ground fuels. We also highlight the critical role of fuel phenology in assessing landscape fuel moisture variations in temperate environments. Conclusions: Understanding the mechanisms driving fuel moisture variability opens opportunities to develop locally robust fuel models for input into wildfire danger rating systems, adding versatility to wildfire danger assessments as a management tool

Characterizing the rate of spread of large wildfires in emerging fire environments of northwestern Europe using visible infrared imaging radiometer suite active fire data

In recent years fires of greater magnitude have been documented throughout northwest Europe. With several climate projections indicating future increases in fire activity in this temperate area, it is imperative to identify the status of fire in this region. This study unravels unknowns about the state of the fire regime in northwest Europe by characterizing one of the key aspects of fire behavior, the rate of spread (ROS). Using an innovative approach to cluster Visible Infrared Imaging Radiometer Suite (VIIRS) hotspots into fire perimeter isochrones to derive ROS, we identify the effects of land cover and season on the rate of spread of 102 landscape fires that occurred between 2012 and 2022. Results reveal significant differences between land cover types, and there is a clear peak of ROS and burned area in the months of March and April. Median ROS within these peak months is approximately 0.09 km h−1 during a 12 h overpass, and 66 % of the burned area occurs in this spring period. Heightened ROS and burned area values persist in the bordering months of February and May, suggesting that these months may present the extent of the main fire season in northwest Europe. Accurate data on ROS among the represented land cover types, as well as periods of peak activity, are essential for determining periods of elevated fire risk, the effectiveness of available suppression techniques, and appropriate mitigation strategies (land and fuel management).This project has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 860787 (PyroLife Innovative Training Network; https://pyrolife.lessonsonfire.eu/, last access: January 2023), a project in which a new generation of experts is trained in integrated fire manageme

A global outlook on increasing wildfire risk:current policy situation and future pathways

International audienc

Climate controls on the mass balance of Brewster Glacier, Southern Alps

Glaciers are highly sensitive indicators of climate variability. From the 1980’s to the early 2000’s, some glaciers in the Southern Alps experienced periods of advance; counter to global trends of glacier recession. These anomalous advances demonstrate the complexity of glacier-climate interactions and indicate the need to understand the physical drivers of glacier mass balance; particularly in the Southern Hemisphere, where long-term mass balance records are limited. To this end, the atmospheric and oceanic drivers of mass balance variability at Brewster Glacier in the Southern Alps are examined in this thesis. These drivers are examined across long and short-term periods, each at hemispheric, synoptic, and glacier spatial scales, using a mass balance record derived from the MODerate-resolution Imaging Spectroradiometer (1979-2013), 22-months of daily weather station data from the ablation zone of Brewster Glacier, as well as reanalysis, statistically downscaled, and station-based climate data sets. The highest mass gain (loss) years are on average driven by negative (positive) anomalies of geopotential height surrounding New Zealand, sea surface temperature, and atmospheric water vapour. The El Niño Southern Oscillation (ENSO) is found to be an important driver of mass balance, with mass gain (loss) years coincident with El Niño (La Niña) episodes. Elevated annual precipitation totals are not found during mass gain years, rather the increased proportion of snowfall and reduced proportion of rainfall as governed by temperature are responsible for mass gain. In terms of regional atmospheric circulation, the occurrence of north westerly airflow is critical for mass balance, delivering cold, wet conditions for accumulation in winter, and warm, wet conditions for melt in summer. The combined turbulent heat fluxes provide the largest source of energy for melt during extreme melt events (60%). For three of the most extreme melt and snowfall events, north westerly circulation is associated with high rates of water vapour flux, which resemble atmospheric river-type structures, the first time such features have been linked to glacier mass balance in New Zealand. The identification of regional scale atmospheric conditions, link to ENSO, and importance of north westerly circulation and associated vapour flux for both extreme melt and snow have contributed to a more holistic understanding of the relationships between mountain glaciers in the Southern Alps and the climate system

Characterizing the rate of spread of large wildfires in emerging fire environments of northwestern Europe using Visible Infrared Imaging Radiometer Suite active fire data

In recent years fires of greater magnitude have been documented throughout northwest Europe. With several climate projections indicating future increases in fire activity in this temperate area, it is imperative to identify the status of fire in this region. This study unravels unknowns about the state of the fire regime in northwest Europe by characterizing one of the key aspects of fire behavior, the rate of spread (ROS). Using an innovative approach to cluster Visible Infrared Imaging Radiometer Suite (VIIRS) hotspots into fire perimeter isochrones to derive ROS, we identify the effects of land cover and season on the rate of spread of 102 landscape fires that occurred between 2012 and 2022. Results reveal significant differences between land cover types, and there is a clear peak of ROS and burned area in the months of March and April. Median ROS within these peak months is approximately 0.09 km h−1 during a 12 h overpass, and 66 % of the burned area occurs in this spring period. Heightened ROS and burned area values persist in the bordering months of February and May, suggesting that these months may present the extent of the main fire season in northwest Europe. Accurate data on ROS among the represented land cover types, as well as periods of peak activity, are essential for determining periods of elevated fire risk, the effectiveness of available suppression techniques, and appropriate mitigation strategies (land and fuel management)