@article{22583, abstract = {Accurately predicting weather and climate in cities is critical for safeguarding human health and strengthening urban resilience. Multimodel evaluations can lead to model improvements; however, there have been no major intercomparisons of urban-focussed land surface models in over a decade. Here, in Phase 1 of the Urban-PLUMBER project, we evaluate the ability of 30 land surface models to simulate surface energy fluxes critical to atmospheric meteorological and air quality simulations. We establish minimum and upper performance expectations for participating models using simple information-limited models as benchmarks. Compared with the last major model intercomparison at the same site, we find broad improvement in the current cohort's predictions of short-wave radiation, sensible and latent heat fluxes, but little or no improvement in long-wave radiation and momentum fluxes. Models with a simple urban representation (e.g., ‘slab’ schemes) generally perform well, particularly when combined with sophisticated hydrological/vegetation models. Some mid-complexity models (e.g., ‘canyon’ schemes) also perform well, indicating efforts to integrate vegetation and hydrology processes have paid dividends. The most complex models that resolve three-dimensional interactions between buildings in general did not perform as well as other categories. However, these models also tended to have the simplest representations of hydrology and vegetation. Models without any urban representation (i.e., vegetation-only land surface models) performed poorly for latent heat fluxes, and reasonably for other energy fluxes at this suburban site. Our analysis identified widespread human errors in initial submissions that substantially affected model performances. Although significant efforts are applied to correct these errors, we conclude that human factors are likely to influence results in this (or any) model intercomparison, particularly where participating scientists have varying experience and first languages. These initial results are for one suburban site, and future phases of Urban-PLUMBER will evaluate models across 20 sites in different urban and regional climate zones.}, author = {Lipson, Mathew J. and Grimmond, Sue and Best, Martin and Abramowitz, Gab and Coutts, Andrew and Tapper, Nigel and Baik, Jong‐Jin and Beyers, Meiring and Blunn, Lewis and Boussetta, Souhail and Bou‐Zeid, Elie and De Kauwe, Martin G. and de Munck, Cécile and Demuzere, Matthias and Fatichi, Simone and Fortuniak, Krzysztof and Han, Beom‐Soon and Hendry, Margaret A. and Kikegawa, Yukihiro and Kondo, Hiroaki and Lee, Doo‐Il and Lee, Sang‐Hyun and Lemonsu, Aude and Machado, Tiago and Manoli, Gabriele and Martilli, Alberto and Masson, Valéry and McNorton, Joe and Meili, Naika and Meyer, David and Nice, Kerry A. and Oleson, Keith W. and Park, Seung‐Bu and Roth, Michael and Schoetter, Robert and Simón‐Moral, Andrés and Steeneveld, Gert‐Jan and Sun, Ting and Takane, Yuya and Thatcher, Marcus and Tsiringakis, Aristofanis and Varentsov, Mikhail and Wang, Chenghao and Wang, Zhi‐Hua and Pitman, Andy J.}, issn = {1477-870X}, journal = {Quarterly Journal of the Royal Meteorological Society}, keywords = {Benchmark, Energy balance, Intercomparison, Model evaluation, Urban climate, Urban meteorology}, number = {758}, pages = {126--169}, publisher = {Wiley}, title = {{Evaluation of 30 urban land surface models in the Urban-PLUMBER project: Phase 1 results}}, doi = {10.1002/qj.4589}, volume = {150}, year = {2024}, } @article{22534, abstract = {Tree planting is a prevalent strategy to mitigate urban heat. Tree cooling efficiency(TCE), defined as the temperature reduction for a 1% tree cover increase, plays animportant role in urban climate as it regulates the capacity of trees to alter the sur-face energy and water budget. However, the spatial variation and more importantly,temporal heterogeneity of TCE in global cities are not fully explored. Here, we usedLandsat-based tree cover and land surface temperature (LST) to compare TCEs at areference air temperature and tree cover level across 806 global cities and to exploretheir potential drivers with a boosted regression tree (BRT) machine learning model.From the results, we found that TCE is spatially regulated by not only leaf area index(LAI) but climate variables and anthropogenic factors especially city albedo, withouta specific variable dominating the others. However, such spatial difference is attenu-ated by the decrease of TCE with tree cover, most pronounced in midlatitude cities.During the period 2000–2015, more than 90% of analyzed cities showed an increas-ing trend in TCE, which is likely explained by a combined result of the increase in LAI,intensified solar radiation due to decreased aerosol content, increase in urban vaporpressure deficit (VPD) and decrease of city albedo. Concurrently, significant urbanafforestation occurred across many cities showing a global city-scale mean tree coverincrease of 5.3 ± 3.8% from 2000 to 2015. Over the growing season, such increasescombined with an increasing TCE were estimated to on average yield a midday sur-face cooling of 1.5 ± 1.3°C in tree-covered urban areas. These results are offeringnew insights into the use of urban afforestation as an adaptation to global warmingand urban planners may leverage them to provide more cooling benefits if trees areprimarily planted for this purpose.}, author = {Zhao, Jiacheng and Zhao, Xiang and Wu, Donghai and Meili, Naika and Fatichi, Simone}, issn = {1365-2486}, journal = {Global Change Biology}, keywords = {Climate change, Remote sensing, Tree cooling efficiency, Tree cover, Urban afforestation}, number = {11}, pages = {3085--3097}, publisher = {Wiley}, title = {{Satellite‐based evidence highlights a considerable increase of urban tree cooling benefits from 2000 to 2015}}, doi = {10.1111/gcb.16667}, volume = {29}, year = {2023}, } @article{22531, abstract = {To make sound decisions in the face of climate change, government agencies, policymakers and private stakeholders require suitable climate information on local to regional scales. In Switzerland, the development of climate change scenarios is strongly linked to the climate adaptation strategy of the Confederation. The current climate scenarios for Switzerland CH2018 - released in form of six user-oriented products - were the result of an intensive collaboration between academia and administration under the umbrella of the National Centre for Climate Services (NCCS), accounting for user needs and stakeholder dialogues from the beginning. A rigorous scientific concept ensured consistency throughout the various analysis steps of the EURO-CORDEX projections and a common procedure on how to extract robust results and deal with associated uncertainties. The main results show that Switzerland’s climate will face dry summers, heavy precipitation, more hot days and snow-scarce winters. Approximately half of these changes could be alleviated by mid-century through strong global mitigation efforts. A comprehensive communication concept ensured that the results were rolled out and distilled in specific user-oriented communication measures to increase their uptake and to make them actionable. A narrative approach with four fictitious persons was used to communicate the key messages to the general public. Three years after the release, the climate scenarios have proven to be an indispensable information basis for users in climate adaptation and for downstream applications. Potential for extensions and updates has been identified since then and will shape the concept and planning of the next scenario generation in Switzerland.}, author = {Fischer, A.M. and Strassmann, K.M. and Croci-Maspoli, M. and Hama, A.M. and Knutti, R. and Kotlarski, S. and Schär, C. and Schnadt Poberaj, C. and Ban, N. and Bavay, M. and Beyerle, U. and Bresch, D.N. and Brönnimann, S. and Burlando, P. and Casanueva, A. and Fatichi, Simone and Feigenwinter, I. and Fischer, E.M. and Hirschi, M. and Liniger, M.A. and Marty, C. and Medhaug, I. and Peleg, N. and Pickl, M. and Raible, C.C. and Rajczak, J. and Rössler, O. and Scherrer, S.C. and Schwierz, C. and Seneviratne, S.I. and Skelton, M. and Sørland, S.L. and Spirig, C. and Tschurr, F. and Zeder, J. and Zubler, E.M.}, issn = {2405-8807}, journal = {Climate Services}, keywords = {Climate scenario, Climate services, Switzerland, EURO-CORDEX, User-oriented communication, National projections}, publisher = {Elsevier}, title = {{Climate Scenarios for Switzerland CH2018 – Approach and Implications}}, doi = {10.1016/j.cliser.2022.100288}, volume = {26}, year = {2022}, } @article{22537, abstract = {Urban heat islands (UHIs) are a widely studied phenomenon, while research on urban-rural differences in humidity, the so called urban dry or moisture islands (UDIs, UMIs), is less common and a large-scale quantification of the seasonal and diurnal patterns of the UDI is still lacking. However, quantification of the UDI/UMI effect is essential to understand the impacts of humidity on outdoor thermal comfort, building energy consumption, and urban ecology in cities worldwide. Here, we use a set of globally distributed air temperature and humidity measurements (1089 stations) to quantify diurnal and seasonal patterns of UHI and UDI resulting from rapid urbanization over many regions of the world. The terms ‘absolute UDI’ and ‘relative UDI’ are defined, which quantify urban–rural differences in actual and relative humidity metrics, respectively. Results show that absolute UDI is largest during daytime with the peak humidity decrease in urban areas occurring during late afternoon hours. In contrast, relative UDI is largest during night and the peak urban relative humidity (RH) decrease and vapor pressure deficit (VPD) increase occurs in the late evening hours with values of around −10% to −11% for RH and 2.9–3.6 hPa for VPD between 20–00 local time during summer. Relative and absolute UDIs are largest during the warm season, except for daytime RH UDI, which does not show any seasonal pattern. In agreement with literature, canopy air UHI is shown to be a nighttime phenomenon, which is larger during summer than winter. Relative UDI is predominantly caused by changes in actual humidity during day and UHI during nighttime.}, author = {Meili, Naika and Paschalis, Athanasios and Manoli, Gabriele and Fatichi, Simone}, issn = {1748-9326}, journal = {Environmental Research Letters}, keywords = {Urban dry island, Urban moisture island, Urban heat island, Urban climate, Urbanization effects, Humidity}, number = {5}, publisher = {IOP Publishing}, title = {{Diurnal and seasonal patterns of global urban dry islands}}, doi = {10.1088/1748-9326/ac68f8}, volume = {17}, year = {2022}, } @article{10568, abstract = {Genetic adaptation and phenotypic plasticity facilitate the migration into new habitats and enable organisms to cope with a rapidly changing environment. In contrast to genetic adaptation that spans multiple generations as an evolutionary process, phenotypic plasticity allows acclimation within the life-time of an organism. Genetic adaptation and phenotypic plasticity are usually studied in isolation, however, only by including their interactive impact, we can understand acclimation and adaptation in nature. We aimed to explore the contribution of adaptation and plasticity in coping with an abiotic (salinity) and a biotic (Vibrio bacteria) stressor using six different populations of the broad-nosed pipefish Syngnathus typhle that originated from either high [14–17 Practical Salinity Unit (PSU)] or low (7–11 PSU) saline environments along the German coastline of the Baltic Sea. We exposed wild caught animals, to either high (15 PSU) or low (7 PSU) salinity, representing native and novel salinity conditions and allowed animals to mate. After male pregnancy, offspring was split and each half was exposed to one of the two salinities and infected with Vibrio alginolyticus bacteria that were evolved at either of the two salinities in a fully reciprocal design. We investigated life-history traits of fathers and expression of 47 target genes in mothers and offspring. Pregnant males originating from high salinity exposed to low salinity were highly susceptible to opportunistic fungi infections resulting in decreased offspring size and number. In contrast, no signs of fungal infection were identified in fathers originating from low saline conditions suggesting that genetic adaptation has the potential to overcome the challenges encountered at low salinity. Offspring from parents with low saline origin survived better at low salinity suggesting genetic adaptation to low salinity. In addition, gene expression analyses of juveniles indicated patterns of local adaptation, trans-generational plasticity and developmental plasticity. In conclusion, our study suggests that pipefish are locally adapted to the low salinity in their environment, however, they are retaining phenotypic plasticity, which allows them to also cope with ancestral salinity levels and prevailing pathogens.}, author = {Goehlich, Henry and Sartoris, Linda and Wagner, Kim-Sara and Wendling, Carolin C. and Roth, Olivia}, issn = {2296-701X}, journal = {Frontiers in Ecology and Evolution}, keywords = {ecology, evolution, behavior and systematics, trans-generational plasticity, genetic adaptation, local adaptation, phenotypic plasticity, Baltic Sea, climate change, salinity, syngnathids}, publisher = {Frontiers Media}, title = {{Pipefish locally adapted to low salinity in the Baltic Sea retain phenotypic plasticity to cope with ancestral salinity levels}}, doi = {10.3389/fevo.2021.626442}, volume = {9}, year = {2021}, } @article{22529, abstract = {Mountainous catchments cover a broad range of elevations and their response to a warming climate is expected to vary significantly in space. Nevertheless, studies on climate change impacts typically examine the changes in flow statistics only at the catchment outlet. In this study, we instead demonstrate the high variability of the hydrological response to climate change at the sub-catchment scale, investigating in detail the contribution of all components of the hydrological cycle in two mountainous catchments (Thur and Kleine Emme) in the Swiss Alps. The analysis was conducted with a two-dimensional weather generator model that simulated gridded climate variables at an hourly and 2-km resolution until the end of the 21st century for the RCP8.5 emission scenario. The climate ensemble was used as input into a distributed hydrological model to estimate the changes in hydrological processes at 100-m and hourly resolutions. Climate models show that precipitation intensifies during winter but weakens during summer in the order of ± 5–10% toward the end of the century. Temperature will rise by up to 4°C, leading to a 50% reduction in snowmelt, 10% increase in evapotranspiration, and shift in precipitation type from snowfall to rainfall. As a result, streamflow is projected to increase by 40% in winter but decrease by 20% to 40% during summer, with winter floods becoming more frequent. The changes to streamflow (mean and extreme low and high flows) at the sub-catchments show a strong dependency with elevation. In contrast to the small changes projected at the outlet of the catchments, streamflow shows a reduction at higher elevations (up to −20% change in mean streamflow for sub-catchments at elevations exceeding 1400 m) and an increase at lower elevations (up to +5% for Kleine Emme and +20% for the Thur at elevations below 600 m). These impacts are tied to the changes in precipitation, as well as changes in snowmelt (at high elevation) and evapotranspiration (at low elevation). The results reveal the causes and diversity of hydrological response to climate change, emphasizing the importance of investigating the distributed impacts of climate change in mountainous environments.}, author = {Moraga, Jorge Sebastián and Peleg, Nadav and Fatichi, Simone and Molnar, Peter and Burlando, Paolo}, issn = {1879-2707}, journal = {Journal of Hydrology}, keywords = {Catchment modelling, Climate change impacts, Weather generator, Distributed hydrological model, Streamflow extremes, Hydrological response}, publisher = {Elsevier}, title = {{Revealing the impacts of climate change on mountainous catchments through high-resolution modelling}}, doi = {10.1016/j.jhydrol.2021.126806}, volume = {603}, year = {2021}, } @article{22442, abstract = {Mountainous running water ecosystems are vulnerable to climate change with major changes coming from warming temperatures. Species distribution will be affected and some species are anticipated to be winners (increasing their range) or losers (at risk of extinction). Climate change vulnerability is seldom integrated when assessing threat status for lists of species at risk (Red Lists), even though this might appear an important addition in the current context. The main objective of our study was to assess the potential vulnerability of Ephemeroptera (E), Plecoptera (P) and Trichoptera (T) species to global warming in a Swiss mountainous region by supplementing Species Distribution Models (SDMs) with a trait-based approach, using available historical occurrence and environmental data and to compare our outcomes with the Swiss National Red List. First, we used nine different modelling techniques and topographic, land use, climatic and hydrological variables as predictors of EPT species distribution. The shape of the response curves of the species for the environmental variables in the nine modelling techniques, together with three biological and ecological traits were used to assess the potential vulnerability of each species to climate change. The joint use of SDMs and trait approach appeared complementary and even though discrepancies were highlighted between SDMs and trait analyses, groups of potential “winners” and “losers” were raised out. Plecoptera appeared as the most vulnerable group to global warming. Divergences between current threat status of species and our results pointed out the need to integrate climate change vulnerability in Red List assessments.}, author = {Besacier Monbertrand, Anne-Laure and Timoner, Pablo and Rahman, Kazi and Burlando, Paolo and Fatichi, Simone and Gonseth, Yves and Moser, Frédéric and Castella, Emmanuel and Lehmann, Anthony}, issn = {2073-4441}, journal = {Water}, keywords = {Species Distribution Models, ensemble forecasting, Swiss Alps, climate change, red lists}, number = {4}, publisher = {MDPI}, title = {{Assessing the vulnerability of aquatic macroinvertebrates to climate warming in a mountainous watershed: Supplementing presence-only data with species traits}}, doi = {10.3390/w11040636}, volume = {11}, year = {2019}, } @article{22527, abstract = {Mountain ecosystems are experiencing rapid warming resulting in ecological changes worldwide. Projecting the response of these ecosystems to climate change is thus crucial, but also uncertain due to complex interactions between topography, climate, and vegetation. Here, we performed numerical simulations in a real and a synthetic spatial domain covering a range of contrasting climatic conditions and vegetation characteristics representative of the European Alps. Simulations were run with the mechanistic ecohydrological model Tethys–Chloris to quantify the drivers of ecosystem functioning and to explore the vulnerability of Alpine ecosystems to climate change. We correlated the spatial distribution of ecohydrological responses with that of meteorological and topographic attributes and computed spatially explicit sensitivities of net primary productivity, transpiration, and snow cover to air temperature, radiation, and water availability. We also quantified how the variance in several ecohydrological processes, such as transpiration, quickly diminishes with increasing spatial aggregation, which highlights the importance of fine spatial resolution for resolving patterns in complex topographies. We conducted controlled numerical experiments in the synthetic domain to disentangle the effect of catchment orientation on ecohydrological variables, such as streamflow. Our results support previous studies reporting an altitude threshold below which Alpine ecosystems are water‐limited in the drier inner‐Alpine valleys and confirm that the wetter areas are temperature‐limited. High‐resolution simulations of mountainous areas can improve our understanding of ecosystem functioning across spatial scales. They can also locate the areas that are the most vulnerable to climate change and guide future measurement campaigns.}, author = {Mastrotheodoros, Theodoros and Pappas, Christoforos and Molnar, Peter and Burlando, Paolo and Hadjidoukas, Panagiotis and Fatichi, Simone}, issn = {1936-0592}, journal = {Ecohydrology}, keywords = {Alpine ecohydrology, Climate change, Ecosystem sensitivity, Numerical modelling, Spatialheterogeneity}, number = {1}, publisher = {Wiley}, title = {{Ecohydrological dynamics in the Alps: Insights from a modelling analysis of the spatial variability}}, doi = {10.1002/eco.2054}, volume = {12}, year = {2019}, } @article{22549, abstract = {The time that rainfall takes to reach the outlet of a catchment as discharge (transit time) is a fundamental and integrated measure of catchment hydrological processes and solute transport mechanisms. As such, many efforts have been dedicated to its understanding and quantification. However, defining and ranking which factors, internal and external to the system, control the distributions of transit time is still an open challenge. Here, we develop a two-stage approach to explore climate and topography controls on transit time, using a fully distributed hydrological model coupled with a transport component. Specifically, we apply the model to two synthetic topographies under five observed climate regimes. With this setup, water fluxes from two years of daily rainfall events are singularly tracked across the catchments to then derive the distributions of transit time and fraction of young water for each combination of topography and climate. Results highlight a considerable variability of transit times in all climates and a pronounced effect of topography within a given climate. They further reveal that for wet climates it is possible to define a curve describing water transit time as a function of cumulative discharge that only depends on topographic properties. On the contrary, in dry climates the variability of transit time and young water fraction is much larger and not amenable to a simple summary. Despite simplifications, quantitative model-based inferences of transit time distributions are useful to better understand how climate and topography affect catchment functioning.}, author = {Remondi, Federica and Botter, Martina and Burlando, Paolo and Fatichi, Simone}, issn = {1879-2707}, journal = {Journal of Hydrology}, keywords = {Transit time distributions, Young water, Climate, Topography, Distributed hydrological modelling}, pages = {37--50}, publisher = {Elsevier}, title = {{Variability of transit time distributions with climate and topography: A modelling approach}}, doi = {10.1016/j.jhydrol.2018.11.011}, volume = {569}, year = {2019}, } @article{22551, abstract = {Exploring the effects of climate change on the hydrological response at the local scale requires climate data at high spatial and temporal resolutions. This is best achieved by generating downscaled ensembles of future climate variables derived from climate models. For this purpose we present a methodology to re-parameterize the AWE-GEN-2d model (Advanced WEather GENerator for a two-dimensional grid). The model simulates key meteorological variables needed by hydrological models and is particularly suitable to explore the effects of stochastic (natural) climatic uncertainty, which is fundamental for hydrological applications, especially at sub-kilometer and hourly scales. Factors of change for different climate statistics are calculated from climate model simulations of present and future climates and subsequently applied to the statistics derived from observations to re-parameterize AWE-GEN-2d. The model abilities in generating an ensemble of future climate variables for the transient period 2020–2089 is presented with examples of precipitation and near-surface air temperature fields from hourly to multi-annual scales for a small mountainous region in the Swiss Alps. The stochastic uncertainty is examined for present and future periods and for spatial scales from the RCM scale (12-km, daily) to 2-km demonstrating the potential use of AWE-GEN-2d outputs. At the RCM scale, model results yield a small increase in annual precipitation (4%) which is within the stochastic uncertainty range for present and future periods (7%). At the fine scale of 2-km, the increase in annual precipitation can exceed the stochastic uncertainty, but for less than 10% of the domain area. On the contrary, changes in annual near-surface air temperature exceed stochastic uncertainty both at the RCM and finer scales. Stochastic climate uncertainty was concluded to be very similar when comparing present and future periods and 12-km and 2-km scales. The benefits of using AWE-GEN-2d in hydrological climate change impact assessments are finally discussed.}, author = {Peleg, Nadav and Molnar, Peter and Burlando, Paolo and Fatichi, Simone}, issn = {1879-2707}, journal = {Journal of Hydrology}, keywords = {Weather generator, Stochastic downscaling, Climate change, Internal climate variability, Climate uncertainty, High-resolution rainfall model}, pages = {627--641}, publisher = {Elsevier}, title = {{Exploring stochastic climate uncertainty in space and time using a gridded hourly weather generator}}, doi = {10.1016/j.jhydrol.2019.02.010}, volume = {571}, year = {2019}, } @article{22540, abstract = {The reliable partitioning of the terrestrial latent heat flux into evaporation (E) and transpiration (T) is important for linking carbon and water cycles and for better understanding ecosystem functioning at local, regional and global scales. Previous research revealed that the transpiration-to-evapotranspiration ratio (T/ET) is well constrained across ecosystems and is nearly independent of vegetation characteristics and climate. Here we investigated the reasons for such a global constancy in present-day T/ET by jointly analysing observations and process-based model simulations. Using this framework, we also quantified how the ratio T/ET could be influenced by changing climate. For present conditions, we found that the various components of land surface evaporation (bare soil evaporation, below canopy soil evaporation, evaporation from interception), and their respective ratios to plant transpiration, depend largely on local climate and equilibrium vegetation properties. The systematic covariation between local vegetation characteristics and climate, resulted in a globally constrained value of T/ET = ∼70 ± 9% for undisturbed ecosystems, nearly independent of specific climate and vegetation attributes. Moreover, changes in precipitation amounts and patterns, increasing air temperatures, atmospheric CO2 concentration, and specific leaf area (the ratio of leaf area per leaf mass) was found to affect T/ET in various manners. However, even extreme changes in the aforementioned factors did not significantly modify T/ET.}, author = {Paschalis, Athanasios and Fatichi, Simone and Pappas, Christoforos and Or, Dani}, issn = {1748-9326}, journal = {Environmental Research Letters}, keywords = {T/ET, Evapotranspiration partitioning, Ecohydrology, Modelling, Climate change}, number = {10}, publisher = {IOP Publishing }, title = {{Covariation of vegetation and climate constrains present and future T/ET variability}}, doi = {10.1088/1748-9326/aae267}, volume = {13}, year = {2018}, } @article{22521, abstract = {A fully distributed hydrological analysis at scales significant for water management for present-day, and projected future climate conditions is presented for a catchment in the Alps. We selected the upper Rhone basin (Switzerland) as a test case for understanding anthropogenic impacts including climate change on water resources and flood risk in the Alpine area. The upper Rhone basin contains reservoirs, river diversions and irrigated areas offering the opportunity to study the interaction between climate change effects and hydraulic infrastructure. Anthropogenic disturbances of the flow regime were implemented in detail in the hydrological analysis. We downscaled climate model realizations using a methodology that accounts for the uncertainty in climate change projections related to the stochastic variability of precipitation and air temperature. We showed how climate change effects on streamflow propagate from high elevation headwater catchments to the river in the main valley by analyzing changes in several hydrological metrics and at various temporal scales across 297 control sections. Changes in the natural hydrological regime imposed by the existing hydraulic infrastructure are likely larger than climate change signals expected by the middle of the 21st century in most of the river network. Despite a strong uncertainty induced by stochastic climate variability, we identified an elevational dependence of climate change impacts with a severe reduction in streamflow due to the missing contribution of water from ice melt at high-elevation and a dampened effect downstream. Reduced ice cover and ice melt are likely to have significant implications for hydropower production. The impacts can emerge without any additional climate warming. A decrease of August–September discharge and an increase of hourly and daily maximum flows appear as plausible projected change for the most part of the catchment. However, it is unlikely that major changes in total runoff for the entire upper Rhone basin will occur in the next four decades.}, author = {Fatichi, Simone and Rimkus, S. and Burlando, P. and Bordoy, R. and Molnar, P.}, issn = {1879-2707}, journal = {Journal of Hydrology}, keywords = {Climate change, Water resources, Stochastic approaches, Ice melt, Alps, Hydrological modeling}, pages = {362--382}, publisher = {Elsevier}, title = {{High-resolution distributed analysis of climate and anthropogenic changes on the hydrology of an Alpine catchment}}, doi = {10.1016/j.jhydrol.2015.03.036}, volume = {525}, year = {2015}, } @article{22493, abstract = {Predictions of a warmer climate over the Great Lakes region due to global change generally agree on the magnitude of temperature changes, but precipitation projections exhibit dependence on which General Circulation Models and emission scenarios are chosen. To minimize model- and scenario-specific biases, we combined information provided by the 3rd phase of the Coupled Model Intercomparison Project database. Specifically, the results of 12 GCMs for three emission scenarios B1, A1B, and A2 were analyzed for mid- (2046–2065) and end-century (2081–2100) intervals, for six locations of a hydroclimatic transect of Michigan. As a result of Bayesian Weighted Averaging, total annual precipitation averaged over all locations and the three emission scenarios increases by 7 % (mid-)–10 % (end-century), as compared to the control period (1961–1990). The projected changes across seasons are non-uniform and precipitation decreases by 3 % (mid-)–5 % (end-) for the months of August and September are likely. Further, average temperature is very likely to increase by 2.02–2.85 °C by the mid-century and 2.58–4.73 °C by the end-century. Three types of non-additive uncertainty sources due to climate models, anthropogenic forcings, and climate internal variability are addressed. When compared to the emission uncertainty, the relative magnitudes of the uncertainty types for climate model ensemble and internal variability are 149 and 225 % for mean monthly precipitation, and they are respectively 127 and 123 % for mean monthly temperature. A decreasing trend of the frost days and an increasing trend of the growing season length are identified. Also, a significant increase in the magnitude and frequency of heavy rainfall events is projected, with relatively more pronounced changes for heavy hourly rainfall as compared to daily events. Quantifying the inherent natural uncertainty and projecting hourly-based extremes, the study results deliver useful information for water resource stakeholders interested in impacts of climate change on hydro-morphological processes.}, author = {Kim, Jongho and Ivanov, Valeriy Y. and Fatichi, Simone}, issn = {1436-3259}, journal = {Stochastic Environmental Research and Risk Assessment}, keywords = {Climate change, Weather generator, Stochastic downscaling, Uncertainty, CMIP3, Internal variability, Emission scenarios, Extreme indicators, The Great Lakes region}, number = {3}, pages = {923--944}, publisher = {Springer Nature}, title = {{Climate change and uncertainty assessment over a hydroclimatic transect of Michigan}}, doi = {10.1007/s00477-015-1097-2}, volume = {30}, year = {2015}, } @article{22545, abstract = {Climate change represents a major increase in uncertainty that water managers and policy makers will need to integrate into water resources policy and management. A certain level of uncertainty has always existed in water resources planning, but the speed and intensity of changes in baseline conditions that climate change embodies might require a shift in perspective. This article draws on both the social and physical science results of the EU-FP7 ACQWA project to better understand the challenges and opportunities for adaptation to climate change impacts on the hydrology of the upper Rhone basin in the Canton Valais, Switzerland. It first presents the results of hydro-climatic change projections downscaled to more temporally and spatially-relevant frames of reference for decision makers. Then, it analyses the current policy and legislative framework within which these changes will take place, according to the policy coherence across different water-relevant frameworks as well as the integration and mainstreaming of climate change. It compares the current policy and legislative frameworks for different aspects of water resources management to the projected impacts of climate change on the hydrology of the upper Rhone basin, in order to examine the appropriateness of the current approach for responding to a changing climatic context. Significant uncertainties pose numerous challenges in the governance context. The study draws on adaptive governance principles, to propose policy actions across different scales of governance to better manage baseline variability as well as more ‘unpredictable’ uncertainty from climate change impacts.}, author = {Clarvis, Margot Hill and Fatichi, Simone and Allan, Andrew and Fuhrer, Jürg and Stoffel, Markus and Romerio, Franco and Gaudard, Ludovic and Burlando, Paolo and Beniston, Martin and Xoplaki, Elena and Toreti, Andrea}, issn = {1873-6416}, journal = {Environmental Science & Policy}, keywords = {Climate change impacts, Adaptation, Water governance, Water management, Rhone basin, Switzerland}, pages = {56--67}, publisher = {Elsevier}, title = {{Governing and managing water resources under changing hydro-climatic contexts: The case of the upper Rhone basin}}, doi = {10.1016/j.envsci.2013.11.005}, volume = {43}, year = {2014}, } @article{22435, abstract = {Regions of vegetation transitions (ecotones) are known to be highly sensitive to climate fluctuations. In this study, the Cellular-Automata Tree Grass Shrub Simulator (CATGraSS) has been modified, calibrated and used with downscaled future climate scenarios to examine the role of climate change on vegetation patterns in a steep mountainous catchment (1.3 km2) located in Sicily, Italy. In the catchment, north-facing slopes are mostly covered by trees and grass, and south-facing slopes by Indian Fig opuntia and grass, with grasses dominating as elevation grows. CATGraSS simulates solar radiation, evapotranspiration, and soil moisture in space and time. Each model cell can hold a single plant type or can be bare soil. Plant competition is modeled explicitly through mortality and the establishment of individual plants in open spaces. In this study, CATGraSS is modified to account for heterogeneity in soil thickness and tested in the study catchment using the historical climate of the region. Predicted vegetation patterns are compared with those obtained from satellite images. Results of model under current climate underscore the importance of solar irradiance and soil thickness, especially in the uplands where soil is shallow, in determining vegetation composition over complex terrain. A stochastic weather generator is used to generate future climate change scenarios for the catchment by downscaling GCM realizations in space and time. Future increase in atmospheric CO2 concentration was considered through modifying the vegetation water use efficiency and stomatal resistance for our study site. Model results suggest that vegetation pattern is highly sensitive to temperature and rainfall variations provided by climate scenarios (30% reduction of the annual precipitation and a 2.8 °C increase of the mean annual temperature). Future climate change is predicted to bring a considerable reorganization of the plant composition following topographic patterns, leading to a decrease of trees cover at the expenses of a grass expansion, which will cause loss of landscape vegetation diversity.}, author = {Caracciolo, Domenico and Noto, Leonardo Valerio and Istanbulluoglu, Erkan and Fatichi, Simone and Zhou, Xiaochi}, issn = {0309-1708}, journal = {Advances in Water Resources}, keywords = {CA model, Climate change, Ecohydrology, Topography}, pages = {159--175}, publisher = {Elsevier}, title = {{Climate change and Ecotone boundaries: Insights from a cellular automata ecohydrology model in a Mediterranean catchment with topography controlled vegetation patterns}}, doi = {10.1016/j.advwatres.2014.08.001}, volume = {73}, year = {2014}, } @article{22459, abstract = {Projections of climate change effects in streamflow are increasingly required to plan water management strategies. These projections are however largely uncertain due to the spread among climate model realizations, internal climate variability, and difficulties in transferring climate model results at the spatial and temporal scales required by catchment hydrology. A combination of a stochastic downscaling methodology and distributed hydrological modeling was used in the ACQWA project to provide projections of future streamflow (up to year 2050) for the upper Po and Rhone basins, respectively located in northern Italy and south-western Switzerland. Results suggest that internal (stochastic) climate variability is a fundamental source of uncertainty, typically comparable or larger than the projected climate change signal. Therefore, climate change effects in streamflow mean, frequency, and seasonality can be masked by natural climatic fluctuations in large parts of the analyzed regions. An exception to the overwhelming role of stochastic variability is represented by high elevation catchments fed by glaciers where streamflow is expected to be considerably reduced due to glacier retreat, with consequences appreciable in the main downstream rivers in August and September. Simulations also identify regions (west upper Rhone and Toce, Ticino river basins) where a strong precipitation increase in the February to April period projects streamflow beyond the range of natural climate variability during the melting season. This study emphasizes the importance of including internal climate variability in climate change analyses, especially when compared to the limited uncertainty that would be accounted for by few deterministic projections. The presented results could be useful in guiding more specific impact studies, although design or management decisions should be better based on reliability and vulnerability criteria as suggested by recent literature.}, author = {Fatichi, Simone and Rimkus, S. and Burlando, P. and Bordoy, R.}, issn = {1879-1026}, journal = {Science of The Total Environment}, keywords = {Climate change, Hydrological modeling, Stochastic downscaling, Uncertainty, Water resources, Alps}, pages = {1171--1182}, publisher = {Elsevier}, title = {{Does internal climate variability overwhelm climate change signals in streamflow? The upper Po and Rhone basin case studies}}, doi = {10.1016/j.scitotenv.2013.12.014}, volume = {493}, year = {2014}, } @article{22556, abstract = {Numerous studies across multiple disciplines search for insights on the effects of climate change at local spatial scales and at fine time resolutions. This study presents an overall methodology of using a weather generator for downscaling an ensemble of climate model outputs. The downscaled predictions can explicitly include climate model uncertainty, which offers valuable information for making probabilistic inferences about climate impacts. The hourly weather generator that serves as the downscaling tool is briefly presented. The generator is designed to reproduce a set of meteorological variables that can serve as input to hydrological, ecological, geomorphological, and agricultural models. The generator is capable of reproducing a wide set of climate statistics over a range of temporal scales, from extremes, to low-frequency interannual variability; its performance for many climate variables and their statistics over different aggregation periods is highly satisfactory. The use of the weather generator in simulations of future climate scenarios, as inferred from climate models, is described in detail. Using a previously developed methodology based on a Bayesian approach, the stochastic downscaling procedure derives the frequency distribution functions of factors of change for several climate statistics from a multi-model ensemble of outputs of General Circulation Models. The factors of change are subsequently applied to the statistics derived from observations to re-evaluate the parameters of the weather generator. Using embedded causal and statistical relationships, the generator simulates future realizations of climate for a specific point location at the hourly scale. Uncertainties present in the climate model realizations and the multi-model ensemble predictions are discussed. An application of the weather generator in reproducing present (1961–2000) and forecasting future (2081–2100) climate conditions is illustrated for the location of Tucson (AZ). The stochastic downscaling is carried out using simulations of eight General Circulation Models adopted in the IPCC 4AR, A1B emission scenario.}, author = {Fatichi, Simone and Ivanov, Valeriy Y. and Caporali, Enrica}, issn = {0309-1708}, journal = {Advances in Water Resources}, keywords = {Weather generator, Stochastic downscaling, Climate change, Hydro-meteorology, Rainfall model}, number = {4}, pages = {448--467}, publisher = {Elsevier}, title = {{Simulation of future climate scenarios with a weather generator}}, doi = {10.1016/j.advwatres.2010.12.013}, volume = {34}, year = {2011}, } @article{22524, abstract = {The analysis of changes in precipitation is nowadays of great interest because rainfall space-time distribution is considered one of the most important indexes in the natural climatic cycle. This study proposes an investigation of precipitation time series recorded in the region of Tuscany (Central Italy) in the period 1916–2003. Forty indexes are defined to evaluate changes in the precipitation patterns and trend detection is performed through statistical tests to assess the significance of temporal and spatial changes in the precipitation regime. The presented analysis does not show strong evidence of nonstationarity. A few indexes in a given number of stations of the analysed territory do show a slight trend, but the significance of those trends is lost once the multiple location testing issue is considered. The complexity of the climate in central Italy, i.e. the presence of numerous feedbacks might in fact distort or remove the consequences of global warming on the precipitation regime. }, author = {Fatichi, Simone and Caporali, Enrica}, issn = {1097-0088}, journal = {International Journal of Climatology}, keywords = {Stationarity, Climate change, Trend, Extreme rainfall, Daily rainfall, Spatial analysis, Multiple testing}, number = {13}, pages = {1883--1893}, publisher = {Wiley}, title = {{A comprehensive analysis of changes in precipitation regime in Tuscany}}, doi = {10.1002/joc.1921}, volume = {29}, year = {2009}, }