Manuela Brunner

Last Name

Brunner

First Name

Manuela

ORCID

0000-0001-8824-877X

Organisational unit

09788 - Brunner, Manuela Irene / Brunner, Manuela Irene

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Publications 1 - 10 of 34

Compounding preconditions of wildfires vary in time and space within Europe
Miller , Julia; Touma , Danielle; Brunner, Manuela (2025)
Communications Earth & Environment
Favorable wildfire conditions are increasing in frequency and severity across Europe. Understanding how wildfire drivers vary in space and time is crucial for mitigating wildfire risk under current and future climate conditions. Here, we analyze the hydro-meteorological and land-surface drivers of wildfires from 2001 to 2020 across eight European climate regions and their mountain ranges. Our findings reveal that drought conditions and vapor pressure deficit are the dominant drivers of wildfire activity. These drivers vary by season and region: in Southern and Central European regions, persistent warm and dry conditions in preceding seasons favor summer wildfires, while fall wildfires are influenced by fuel build up in spring that loses moisture during dry and hot summer weather. In Northern Europe, these dynamics occur on sub-monthly timescales. Our results illustrate the critical role of compounding wildfire drivers and emphasize the need for targeted mitigation strategies, especially in the light of climate change.
Increasing Hydroclimatic Whiplash Can Amplify Wildfire Risk in a Warming Climate
Swain, Daniel L.; Abatzoglou, John T.; Albano, Christine M.; et al. (2025)
Global Change Biology
Impact of bias adjustment strategy on ensemble projections of hydrological extremes
Astagneau, Paul; Wood , Raul R.; Vrac , Mathieu; et al. (2025)
Hydrology and Earth System Sciences
Hydrological climate change impact studies typically rely on hydrological projections generated by hydrological models driven with bias-adjusted climate simulations. Such hydrological projections are influenced by internal climate variability, which can mask the emergence of robust climate trends. To account for internal variability in climate projections, single-model initial-condition large ensembles (SMILEs) can be employed. SMILEs are generated by running a single global/regional climate model many times with slightly perturbed initial conditions. However, it remains challenging to select an appropriate bias adjustment strategy for SMILEs used in hydrological impact studies because of the relative importance of inter-variable dependence and the preservation of both climate variability and the change signal. To facilitate such selection, we here compare different bias adjustment strategies applied to SMILEs and their effect on hydrological impact assessments. Specifically, we investigate how climate and hydrological extremes change for 87 catchments in the Swiss Alps when using (a) univariate vs. bivariate, (b) ensemble vs. individual-member, and (c) change-preserving vs. non-change-preserving bias adjustment methods. To do so, we adjust the biases of a 50-member SMILE with the different adjustment methods and drive a hydrological model to simulate and project high and low flows. Our comparison shows (1) no clear benefits from using bivariate instead of univariate bias adjustment methods when the SMILE already efficiently simulates the dependence between temperature and precipitation and (2) that the choice of using ensemble vs. individual-member and change-preserving vs. non-change-preserving bias adjustments leads to large differences in the values of signal robustness indicators, including temperature, precipitation and streamflow signal-to-noise ratios and streamflow and precipitation time-of-emergence. These influences need to be considered when selecting an appropriate bias adjustment strategy for a given application. Based on our comparison, we generally recommend to apply change-preserving and ensemble bias adjustment methods in future hydrological impact studies using SMILEs. Further research is needed to improve bias adjustment methods that preserve both the signal and the variability of ensemble climate projections.
The Needs, Challenges, and Priorities for Advancing Global Flood Research
Samadi, Vidya; Fowler, Hayley J.; Lamond, Jessica; et al. (2025)
Wiley Interdisciplinary Reviews. Water
In recent years, numerous flood events have caused loss of life, widespread disruption, and damage across the globe. These devastating impacts highlight the importance of a better understanding of flood generating processes, their impacts, and their variability under climate and landscape changes. Here, we argue that the ability to better model flooding is underpinned by the grand challenge of understanding flood generation mechanisms and potential impacts. To address this challenge, the World Meteorological Organization-Global Energy and Water Exchanges (GEWEX) Hydrometeorology Panel (GHP) aims to establish a Global Flood Crosscutting project to propagate flood modeling and research knowledge across regions and to synthesize results at the global scale. This paper outlines a framework for understanding the dynamics and impacts of runoff generation processes and a rationale for the role of a Global Flood Crosscutting project to address these challenges. Within this Global Flood Crosscutting project, we will establish a common terminology and methods to enable the global research community to exchange knowledge and experiences, and to design experiments toward developing actionable recommendations for more effective flood management practices and policies for improved resilience. This harmonization of rich perspectives across disciplines will foster the co-production of knowledge primed to advance flood research, particularly in the current period of heightened climate variability and rapid change. It will create a new transdisciplinary paradigm for flood science, wherein different dimensions of mechanistic understanding and processes are rigorously considered alongside socioeconomic impacts, early warning communications, and longer-term adaptation to alleviate flood risks in society.
Snow drought propagation and its impacts on streamflow drought in the Alps
Chartier-Rescan, Corentin; Wood, Raul R.; Brunner, Manuela (2025)
Environmental Research Letters
Snow droughts, that is negative anomalies in annual snow storage, challenge water resources management in snow-rich catchments and their downstream regions because they can lead to succeeding streamflow droughts in the following melt season. Under continued global warming, snow droughts are expected to become more frequent and intense, which likely increases the occurrence of succeeding streamflow droughts. However, we still know little about the rate at which snow droughts propagate to subsequent streamflow droughts, the spatial patterns of these concurrent events, the influence of snow drought characteristics on the occurrence, deficit, and duration of streamflow droughts, and temporal changes in snow drought propagation. To address these research gaps, we developed a novel dynamic bi-directional snow-to-streamflow drought propagation scheme, that resulted in a unique dataset of concurrent snow and streamflow droughts for 207 catchments in Switzerland and Austria. We found that in the period from 1961 to 2020, 18% of the snow droughts propagated to a streamflow drought, and that 21% of the spring/summer streamflow droughts were preceded by a snow drought. Snow-to-streamflow droughts are most common in catchments at high elevations without glaciers and among the snow droughts with the largest deficits and longest durations. In general, snow droughts lead to streamflow droughts with higher deficits, longer durations, and earlier occurrences. In the last six decades, the number of snow droughts has increased, which resulted in a doubling of snow-to-streamflow drought events in 1991-2020 compared to 1961-1990. As snow droughts are expected to further increase due to climate change, the propagation of snow-to-streamflow droughts will likely increase in medium to high elevation catchments and lead to more frequent and intense spring and summer droughts in the Alps.
Spatially Compounding Drought-Flood Events Are Favored by Atmospheric Blocking Over Europe
Brunner, Manuela; Mittermeier , Magdalena; Anderson , Bailey; et al. (2025)
Water Resources Research
Droughts and floods can occur simultaneously at the continental scale, resulting in impacts from both excess and deficit of water at the same time. Such spatially compounding drought-flood events can result in contrasting water management challenges. Despite their relevance for insurance and management, we know little about their occurrence, seasonality, and large-scale atmospheric drivers. We address this research gap by studying spatially compounding drought-flood events using streamflow and precipitation observations in Europe. Our results show that these compounding events have a strong seasonality and occur most often during winter, spring, and in June, even though their meteorological counterpart, spatially compounding dry-wet extremes, mainly occur in summer. Each of these events has its own spatial footprint. These footprints can be categorized in four main clusters, with the flood part of the compounding extreme either occurring over Central Europe or the UK in summer or winter, Eastern Europe in spring, or Southern Europe in winter. Our analysis of the relationship between seven European weather regimes and spatially compounding drought-flood events shows that these events are mainly favored by different types of blocking regimes in winter, spring, and summer and by the Zonal Regime in winter and spring. These weather regimes are all related to stable high-pressure systems located over one part of Europe and cyclonic conditions at their edges over another part of Europe. We conclude that spatially compounding drought-flood events are favored by particular weather regimes, whose relative importance depends on the season and the location of the flood hotspot.
Hydrological Whiplash: Highlighting the Need for Better Understanding and Quantification of Sub-Seasonal Hydrological Extreme Transitions
Hammond, John; Anderson, Bailey; Simeone, Caelan; et al. (2025)
Hydrological Processes
In this commentary, we aim to (1) describe ways that hydrological intensification and hydrological whiplash (sub-seasonal transitions between hydrological extremes) may impact water management decision-making, (2) introduce the complexities of identifying and quantifying hydrological extreme transitions, (3) discuss the processes controlling hydrological transitions and trends in hydrological extremes through time, (4) discuss considerations involved in modeling hydrological extreme transitions, and (5) motivate additional research by suggesting priority research questions that diverge from an assumption of independence between extreme events.
What is a drought-to-flood transition? Pitfalls and recommendations for defining consecutive hydrological extreme events
Anderson , Bailey J.; Muñoz-Castro, Eduardo; Tallaksen , Lena M.; et al. (2025)
Hydrology and Earth System Sciences
Research into rapid transitions between hydrological drought and flood is growing in popularity, in part due to media-reported catastrophic impacts from recent events. Droughts and floods are typically studied as events that are independent from one another. Thus, a clear definition and assessment of the methods used to define consecutive drought-to-flood transition events does not yet exist. Here, we use a series of eight catchments that have experienced real-world impacts from drought-to-flood transitions as case studies. We assess the suitability of and differences between event selection methods applied to observational data. We demonstrate that different threshold level methods can alter the characteristics of selected events. The number and timing of transitions differs substantially between threshold level approaches in highly seasonal regimes as opposed to those with a weaker seasonality. The time period used to define the maximum interval between drought and flood also influences whether transitions are detected. We show that the probability of a transition occurring within a set time window could vary substantially between different methodologies and catchments. We also show that previously applied methodologies would likely fail to detect transition events that have been broadly impactful in the historical record. For the eight case study events taken from media, governmental and scientific reports, only three of the transitions were successfully detected. We qualitatively assessed the streamflow time series of the case study catchments, and outline a number of potential pitfalls in the event detection process. Finally, we make recommendations regarding methodological choices in the context of potential impacts of interest, and outline some priorities for future methodological development and research.
Hyper-resolution large-scale hydrological modelling benefits from improved process representation in mountain regions
Janzing , Joren; Wanders , Niko; van Tiel, Marit; et al. (2025)
Hydrology and Earth System Sciences
Many of the world's major rivers originate in mountain regions, and a large fraction of the global population relies on these regions for their water supply. The hydrological cycle of mountain regions and their dependent downstream regions are often studied using large-scale to global hydrological models (LHMs). The increasing spatial resolution of these models allows for improved representation of complex mountain topography, but existing model deficiencies in cold and high-elevation regions limit potential model performance gains. Such model performance gains might be realized by investing in a better representation of hydrological processes that are relevant in mountain regions such as snow accumulation and snowmelt. However, how much improved process representation would increase LHM performance remains largely unquantified. Here, we set up the hyper-resolution 30 arcsec (approx. 1 km) global hydrological model PCR-GLOBWB 2.0 (PCRaster Global Water Balance) over the larger Alpine domain and implement several changes to make it better suited for representing hydrological processes in mountain regions. These changes include (a) the use of novel high-resolution meteorological forcing datasets, (b) an extended snow module based on a seasonally varying degree-day factor and an exponential melt function, (c) a regional calibration of the snow module against a snow reanalysis product, (d) a new integrated glacier module, and (e) an adjusted runoff partitioning scheme that increases the contributions to the fast-runoff components in the soil. Our evaluation of the effect of these different adjustments on model performance for discharge shows that, while the meteorological forcing has a major effect on discharge simulations, it results in a mixed pattern of performance gains and losses over the domain. In addition, the structural and parametric changes, i.e. the snow module modification, glacier representation, and runoff partitioning, improve discharge simulations in mountain regions: the snow module modification leads to an improved representation of the snowmelt peak for high-elevation catchments, the glacier module supplies additional water to glacierized catchments, and runoff partitioning in the soil improves the representation of streamflow in flashy catchments at lower elevations. We use these insights to present a new setup of the large-scale and hyper-resolution PCR-GLOBWB 2.0 model that is better suited to studying hydrological processes in and beyond mountain regions around the world.
Spatial variability in Alpine reservoir regulation: Deriving reservoir operations from streamflow using generalized additive models
Brunner, Manuela; Naveau, Philippe (2023)
Hydrology and Earth System Sciences
Reservoir regulation affects various streamflow characteristics, from low to high flows, with important implications for downstream water users. However, information on past reservoir operations is rarely publicly available, and it is hardly known how reservoir operation signals, i.e. information on when water is stored in and released from reservoirs, vary over a certain region. Here, we propose a statistical model to reconstruct reservoir operation signals in catchments without information on reservoir operation. The model uses streamflow time series observed downstream of a reservoir that encompass a period before and a period after a known year of reservoir construction. In a first step, a generalized additive model (GAM) regresses the streamflow time series from the unregulated pre-reservoir period on four covariates including temperature, precipitation, day of the year, and glacier mass balance changes. In a second step, this GAM, which represents natural conditions, is applied to predict natural streamflow, i.e. streamflow that would be expected in the absence of the reservoir, for the regulated period. The difference between the observed regulated streamflow signal and the predicted natural baseline should correspond to the reservoir operation signal. We apply this approach to reconstruct the seasonality of reservoir regulation, i.e. information on when water is stored in and released from a reservoir, from a dataset of 74 catchments in the central Alps with a known reservoir construction date (i.e. date when the reservoir went into operation). We group these reconstructed regulation seasonalities using functional clustering to identify groups of catchments with similar reservoir operation strategies. We show how reservoir management varies by catchment elevation and that seasonal redistribution from summer to winter is strongest in high-elevation catchments. These elevational differences suggests a clear relationship between reservoir operation and climate and catchment characteristics, which has practical implications. First, these elevational differences in reservoir regulation can and should be considered in hydrological model calibration. Furthermore, the reconstructed reservoir operation signals can be used to study the joint impact of climate change and reservoir operation on different streamflow signatures, including extreme events.

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Manuela Brunner

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