| 1. |
- Andersson, Lotta, et al.
(author)
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Local early warning systems for drought - Could they add value to nationally disseminated seasonal climate forecasts?
- 2020
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In: Weather and Climate Extremes. - : ELSEVIER. - 2212-0947. ; 28
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Journal article (peer-reviewed)abstract
- Limited application and use of forecast information restrict smallholder farmers ability to deal with drought in proactive ways. This paper explores the barriers that impede use and uptake of seasonal climate forecasts (SCF) in two pilot communities in Limpopo Province. Current interpretation, translation and mediation of national SCF to the local context is weak. A local early warning system (EWS) was developed that incorporated hydrological modelled information based on national SCF, locally monitored rainfall and soil moisture by a wireless sensor network, and signs from indigenous climate indicators. We assessed to what degree this local EWS could improve interpretation of SCF and increase understanding and uptake by farmers. Local extension staff and champion farmers were found to play important knowledge brokering roles that could be strengthened to increase trust of SCF. The local EWS provided added value to national SCF by involving community members in local monitoring, enacting knowledge interplay with indigenous knowledge and simplifying and tailoring SCF and hydrological information to the local context. It also helped farmers mentally prepare for upcoming conditions even if many do not currently have the adaptive mindsets, economic resources or pre-conditions to positively respond to SCF information.
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| 2. |
- Dyrrdal, Anita Verpe, et al.
(author)
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Changes in design precipitation over the Nordic-Baltic region as given by convection-permitting climate simulations
- 2023
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In: Weather and Climate Extremes. - 2212-0947. ; 42
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Journal article (peer-reviewed)abstract
- The increased risk of flooding due to global warming and subsequent heavy rainfall events in the Nordic-Baltic region, call for recommendations directed at long-term planning. One example of such recommendations are climate change allowances. These are often based on expected changes in design precipitation as given by climate model simulations, and are used as a buffer on top of current design values to avoid a future increased damage potential as a consequence of climate change. We here compute expected changes in precipitation design values, so-called climate factors (CFs), for the Nordic-Baltic region, based on 3 km convection permitting simulations from the Nordic Convection Permitting Climate Projections project. These have the advantage of explicitly resolving convection, which has been shown to be the main contributor to increased rainfall. We assess the dependence of the CFs on rainfall duration, return period, and geographical location, focusing on the summer (convective) season, short durations and the high emission scenario RCP8.5. We also compare these CFs to those computed from a non-convection permitting regional climate model ensemble. We found higher CFs for the longer return period, with only few exceptions, and distinctly higher CFs going from daily to sub-daily durations. However, the different simulations give conflicting results for very short-duration rainfall (<3 h). The huge difference in the climate sensitivity of driving GCMs dominates the magnitude of estimated return levels. Our analysis is shaped by the high computational costs of running convection permitting models, resulting in a very limited ensemble (3 members) representing a single emission scenario (RCP8.5). Therefore, we believe that combining results from convection permitting simulations with a larger ensemble (21 members) of non-convection permitting simulations adds value to the assessment of robust climate change allowances for heavy precipitation in the Nordic-Baltic region.
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| 3. |
- Ficchì, Andrea, et al.
(author)
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Beyond El Niño : Unsung climate modes drive African floods
- 2021
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In: Weather and Climate Extremes. - : Elsevier BV. - 2212-0947. ; 33
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Journal article (peer-reviewed)abstract
- The El Nino Southern Oscillation (ENSO) dominates the conversation about predictability of climate extremes and early warning and preparedness for floods and droughts, but in Africa other modes of climate variability are also known to influence rainfall anomalies. In this study, we compare the role of ENSO in driving flood hazard over sub-Saharan Africa with modes of climate variability in the Indian and Atlantic Oceans. This is achieved by applying flood frequency approaches to a hydrological reanalysis dataset and streamflow observations for different phases of the ENSO, Indian Ocean Dipole and Tropical South Atlantic climate modes.Our results highlight that Indian and Atlantic Ocean modes of climate variability are equally as important as ENSO for driving changes in the frequency of impactful floods across Africa. We propose that in many parts of Africa a larger consideration of these unsung climate modes could provide improved seasonal predictions of associated flood hazard and better inform adaptation to the changing climate.
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| 4. |
- Leeding, Richard, et al.
(author)
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Modulation of North Atlantic extratropical cyclones and extreme weather in Europe during North American cold spells
- 2023
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In: Weather and Climate Extremes. - : Elsevier. - 2212-0947. ; 42
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Journal article (peer-reviewed)abstract
- Recent research has established a statistical link between North American cold spells (CS) and concurrent wet or windy extremes in Europe. Here, we investigate whether such a link can be related to changes in the characteristics of North Atlantic extratropical cyclones (hereafter cyclones). Despite large regions of anomalous baroclinicity during periods of North American CS, the number of cyclones across the North Atlantic as a whole is not significantly above climatology. However, we observe rates of explosive cyclogenesis significantly above climatology. We further find that CS over different North American regions are associated with large-scale atmospheric configurations displaying a strenghtened jet stream in the vicinity of the CS and different upper-level wind anomalies in the East Atlantic. These, in turn, modulate the regional distributions and characteristics of cyclones in the North Atlantic and Europe. We compute a fixed-radius cyclone footprint which we use to associate extreme precipitation and wind occurrences to individual cyclones. For eastern Canada CS, the North Atlantic jet extends over Northern Europe, resulting in a heightened numbers of cyclones for the British Isles and Scandinavia, while France, the British Isles, Northern Europe and Scandinavia all experience more intense cyclones. The British Isles consistently experience wind extremes associated with cyclones during east Canada CS. For central Canada CS, the jet is displaced poleward and only partly extends over Europe, resulting in an above average cyclone density in the eastern Atlantic and a higher number of cyclones affecting Iberia only. Iberia consistently experiences precipitation extremes associated with the cyclones during central Canada CS. For eastern United States CS, the jet is displaced equatorward and extends over Southern Europe, with a significantly heightened number of cyclones affecting Iberia and France. Iberia experiences wind extremes associated with the cyclones during eastern United States CS. Our results provide a dynamical explanation for previous statistical findings on the concurrence of North American CS and wet or windy extremes over Europe.
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| 5. |
- Leeding, Richard, et al.
(author)
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On Pan-Atlantic cold, wet and windy compound extremes
- 2023
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In: Weather and Climate Extremes. - : Elsevier BV. - 2212-0947. ; 39
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Journal article (peer-reviewed)abstract
- The co-occurrence of extreme weather in geographically distinct regions can result in larger impacts than the sum of those associated with the individual events occurring in isolation. Previous work has proposed a connection between extreme cold temperatures over North America and wet and windy weather over Europe. Here, we present a systematic statistical analysis of this link, focusing on extreme occurrences in both continents. We identify wintertime cold air outbreaks (CAOs) for 38 overlapping domains over North America between 1979 and 2020 using ERA5 data. The occurrence of these regional CAOs is then matched to extreme precipitation and wind events over 6 domains in western and central Europe. We find CAOs over the eastern and central USA co-occur with more frequent wind extremes over Iberia, whilst CAOs over eastern Canada are followed by wind extremes over northern Europe and the British Isles. Precipitation extremes exhibit greater variability and typically occur prior to the peak of the CAOs. We find significant increases in Iberian and southern European precipitation extremes occurring in conjunction with CAOs over the eastern USA, consistent with what we found for wind extremes. Indeed, Iberia is one of the hotspot regions for wet and windy extremes co-occurring with CAOs in North America: depending on CAO region, the frequency of extreme precipitation and wind events over Iberia locally can more than double relative to climatology. Results indicate that the location of wet and windy European extremes substantially depends on the North American region affected by CAOs. Although pan-Atlantic extremes are associated with an enhanced upper-level jet stream, their complete dynamical description requires further investigation.
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| 6. |
- Martins, Leila Droprinchinski, et al.
(author)
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Extreme value analysis of air pollution data and their comparison between two large urban regions of South America
- 2017
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In: Weather and Climate Extremes. - : Elsevier BV. - 2212-0947. ; 18, s. 44-54
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Journal article (peer-reviewed)abstract
- Sixteen years of hourly atmospheric pollutant data (1996-2011) in the Metropolitan Area of São Paulo (MASP), and seven years (2005-2011) of data measured in the Metropolitan Area of Rio de Janeiro (MARJ), were analyzed in order to study the extreme pollution events and their return period. In addition, the objective was to compare the air quality between the two largest Brazilian urban areas and provide information for decision makers, government agencies and civil society. Generalized Extreme Value (GEV) and Generalized Pareto Distribution (GPD) were applied to investigate the behavior of pollutants in these two regions. Although GEV and GPD are different approaches, they presented similar results. The probability of higher concentrations for CO, NO, NO2, PM10 and PM2.5 was more frequent during the winter, and O3 episodes occur most frequently during summer in the MASP. On the other hand, there is no seasonally defined behavior in MARJ for pollutants, with O3 presenting the shortest return period for high concentrations. In general, Ibirapuera and Campos Elísios stations present the highest probabilities of extreme events with high concentrations in MASP and MARJ, respectively. When the regions are compared, MASP presented higher probabilities of extreme events for all analyzed pollutants, except for NO; while O3 and PM2.5 are those with most frequent probabilities of presenting extreme episodes, in comparison other pollutants.
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| 7. |
- Moemken, Julia, et al.
(author)
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Windstorm losses in Europe - What to gain from damage datasets
- 2024
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In: Weather and Climate Extremes. - : Elsevier. - 2212-0947. ; 44
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Journal article (peer-reviewed)abstract
- Windstorms are among the most impacting natural hazards affecting Western and Central Europe. Information on the associated impacts and losses are essential for risk assessment and the development of adaptation and mitigation strategies. In this study, we compare reported and estimated windstorm losses from five datasets belonging to three categories: Indices combining meteorological and insurance aspects, natural hazard databases, and loss reports from insurance companies. We analyse the similarities and differences between the datasets in terms of reported events, the number of storms per dataset and the ranking of specific storm events for the period October 1999 to March 2022 across 21 European countries. A total of 94 individual windstorms were documented. Only 11 of them were reported in all five datasets, while the large majority (roughly 60%) was solely recorded in single datasets. Results show that the total number of storms is different in the various datasets, although for the meteorological indices such number is fixed a priori. Additionally, the datasets often disagree on the storm frequency per winter season. Moreover, the ranking of storms based on reported/estimated losses varies in the datasets. However, these differences are reduced when the ranking is calculated relative to storm events that are common in the various datasets. The results generally hold for losses aggregated at European and at country level. Overall, the datasets provide different views on windstorm impacts. Thus, to avoid misleading conclusions, we use no dataset as “ground truth” but treat all of them as equal. We suggest that these different views can be used to test which features are relevant for calibrating windstorm models in specific regions. Furthermore, it could enable users to assign an uncertainty range to windstorm losses. We conclude that a combination of different datasets is crucial to obtain a representative picture of windstorm associated impacts.
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| 8. |
- Pascual, Didac, et al.
(author)
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Increasing impacts of extreme winter warming events on permafrost
- 2022
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In: Weather and Climate Extremes. - : Elsevier BV. - 2212-0947. ; 36
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Journal article (peer-reviewed)abstract
- Winter warming events (WWE) are abrupt and short-lasting (hours-to-days) events of extraordinarily warm weather occurring during wintertime, sometimes accompanied by rainfall (rain on snow events; ROS). Through direct heat transfer and changes in the snowpack properties, these events cause changes in the below-ground thermal regime that, in turn, controls a suite of ecosystem processes ranging from microbial activity to permafrost and vegetation dynamics. In addition, the overall impacts of WWE on ground temperatures may also depend on the timing of the events and the preceding snowpack characteristics. The frequency and intensity of these events in the Arctic, including the Swedish subarctic, has increased remarkably during the recent decades and is expected to increase even further during the 21st Century. In addition, snow depth (not necessarily snow duration) is projected to increase in many parts of the Arctic. In 2005, a manipulation experiment was set up on a lowland permafrost mire in the Swedish subarctic, to simulate projected future increases in winter precipitation. In this study, we analyse this 15-year record of ground temperature, AL thickness, and meteorological variables, to evaluate the influence of different types and timings of WWE on permafrost under different snowpack conditions. We found that all WWE types were strongly linked to permafrost warming in both the ambient and the manipulated plots during the winter months, but that significantly warmer summer ground temperatures and, consequently, thicker active layer (AL) were only linked to ROS events in manipulated plots. Additional long-term AL thickness data from nearby permafrost sites indicate an increasingly stronger influence of WWE over time since the mid-1990s, to the detriment of the influence of summer air temperatures.
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| 9. |
- Pons, Flavio Maria Emanuele, et al.
(author)
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Simulating the Western North America heatwave of 2021 with analogue importance sampling
- 2024
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In: Weather and Climate Extremes. - : Elsevier. - 2212-0947. ; 43
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Journal article (peer-reviewed)abstract
- During the summer of 2021, the North American Pacific Northwest was affected by an extreme heatwave that broke previous temperature records by several degrees. The event caused severe impacts on human life and ecosystems, and was associated with the superposition of concurrent drivers, whose effects were amplified by climate change. We evaluate whether this record-breaking heatwave could have been foreseen prior to its observation, and how climate change affects North American Pacific Northwest worst-case heatwave scenarios. To this purpose, we use a stochastic weather generator with empirical importance sampling. The generator simulates extreme temperature sequences using circulation analogues, chosen with an importance sampling based on the daily maximum temperature over the region that recorded the most extreme impacts. We show how some of the large-scale drivers of the event can be obtained form the circulation analogues, even if such information is not directly given to the stochastic weather generator.
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| 10. |
- Pons, Flavio Maria Emanuele, et al.
(author)
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Simulating the Western North America heatwave of 2021 with analogue importance sampling
- 2024
-
In: Weather and Climate Extremes. - : Elsevier. - 2212-0947. ; 43
-
Journal article (peer-reviewed)abstract
- During the summer of 2021, the North American Pacific Northwest was affected by an extreme heatwave that broke previous temperature records by several degrees. The event caused severe impacts on human life and ecosystems, and was associated with the superposition of concurrent drivers, whose effects were amplified by climate change. We evaluate whether this record-breaking heatwave could have been foreseen prior to its observation, and how climate change affects North American Pacific Northwest worst-case heatwave scenarios. To this purpose, we use a stochastic weather generator with empirical importance sampling. The generator simulates extreme temperature sequences using circulation analogues, chosen with an importance sampling based on the daily maximum temperature over the region that recorded the most extreme impacts. We show how some of the large-scale drivers of the event can be obtained form the circulation analogues, even if such information is not directly given to the stochastic weather generator.
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