Margarida Lopes Rodrigues Liberato

North Atlantic extratropical cyclones propagate towards Northern Europe and are one of the major natural hazards in mid-latitudes. The 2026 winter season witnessed an unprecedented number of named storms in southwestern Europe, resulting in fatalities and significant adverse impacts across the Iberian Peninsula. While windstorm Kristin was the most impactful event, featuring record-breaking observed wind gusts exceeding 200 km/h and disrupted power grid for weeks in Portugal among other damages, the sequence of subsequent cyclones throughout February, leading to saturated soils that resulted in severe flooding, exacerbated the disruption of critical infrastructure and transport networks.As countries in southwestern Europe are not frequently affected by severe windstorms, a comprehensive assessment of the large-scale synoptic evolution and of the dynamical mechanisms that forced the unusual cyclone explosive development and sting jet associated with windstorm Kristin (27–28 January 2026) is presented, together with a description of the associated meteorological and socioeconomic adverse impacts. The study also considers the consecutive extratropical cyclones and their impact on the hydrological cycle of mainland Portugal. For this purpose, an objective lagrangean method, which identifies and follows individual lows, is applied for the assessment of the cyclone tracks and lifetime characteristics, which is complemented by the analysis of several thermohydrodynamical ERA5 reanalysis fields during the lifetime of the cyclones. A climatological analysis for the extended winter (October to April) on the period 1931-2026 is also performed, putting the 2026 winter season into perspective.Recent studies document that windstorms affecting the Iberian Peninsula may have different characteristics and underlying mechanisms; they are not rare events, and their frequency of occurrence undergoes strong multidecadal variability. Research also highlights the complexity of rainfall patterns, and the need for disentangling natural variability from long-term trends in the region. By presenting other historical extreme winter seasons and high-impact events, this analysis will discuss how rare this season was and propose measures for improving awareness and preparedness, at the local scale, for high-impact climate events occurring in Portugal. This research is performed in the framework of project DouroRisk - prevention and mitigation of natural hazards at the local scale.

The Amazon Basin (AB), the largest hydrographic basin in the world, spans across seven countries in South America. It constitutes a highly intricate system, rich in natural resources, and is marked by substantial biological heterogeneity. The AB plays a pivotal role in the regulation of environmental processes, serving a key component of the global hydrological cycle and climate systems. Understanding the increasing frequency, intensity and spatial extent of extreme drought events in this region is vital for safeguarding the regional ecosystem. This study aims to classify extreme drought events in the AB using the Standardized Precipitation-Evapotranspiration Index (SPEI), derived from ERA5 reanalysis data, covering the period from 1980 to 2024. To assess both agricultural and hydrological droughts, this research incorporates the accumulation periods of 6 and 12 months (SPEI-6 and SPEI-12). The ranking methodology accounts for various SPEI time scales, the extent of the affected area, and the average SPEI intensity within that area. The results highlight that the 2023/24 drought episode was the most intense ever recorded in the AB, with over 90% (80%) of the region affected for the month of January for SPEI-6 (SPEI-12), surpassing known past mega-events, such as the 2005, 2010 and 2015/16 episodes. These extreme conditions were observed across all timespans. Specifically, for January 2024 under the SPEI-6 and for September 2024 under the SPEI-12, more than half of the AB was categorized as experiencing exceptional drought, as established by the 1st percentile of the SPEI distribution. Furthermore, the results underscore the persistence of consecutive periods of drought, especially since the beginning of 2020. With the climate projections indicating continued warming in the region, increased evapotranspiration and lower rates of rainfall are expected, potentially leading to even drier periods. This marks the significance of studies focused on understanding the development and impacts of droughts, as they play a critical role in the mitigation of future environmental risks.

This systematic review examines the potential of hydrogen fuel cell electric vehicles (HFCEVs) and battery electric vehicles (BEVs) as sustainable alternatives to traditional internal combustion vehicles (ICEs) based on fossil fuels in transitioning to greener mobility. By exploring recent literature and applying PRISMA guidelines, we focus on key aspects such as the technological performance, cost-effectiveness, and environmental impact of HFCs compared to EVs. The review emphasizes the critical role of hydrogen production, mainly green hydrogen, and the challenges associated with refueling infrastructure and market viability. Analyzing selected studies, we present insights into the advantages, obstacles, and prospects of HFCEVs in the context of global efforts toward sustainable transportation.

The Amazon Basin (AB) is experiencing an intensification of hydroclimatic extremes, with droughts becoming more frequent, widespread, longer, and severe in the 21st-century. While precipitation deficits have historically been the primary driver of these events, the role of rising air temperatures and the consequent increase of atmospheric evaporative demand (AED) remains poorly quantified. Understanding the relative contributions of these factors is crucial for assessing AB resilience and potential tipping points under ongoing global warming. Here, we analyzed drought evolution across the AB over 45 years (1980–2024) using the Standardized Precipitation-Evapotranspiration Index (SPEI) derived from ERA5-Land reanalysis data. To isolate the contribution of atmospheric evaporative demand (CAED) to drought severity, we compared the standard SPEI with a modified SPEI version based on constant climatological AED.Furthermore, we applied a rarity index to systematically rank drought events by intensity and spatial extent, enabling a standardized comparison of the exceptional 2023/24 event with historical benchmarks. Our analysis reveals that the 2023/24 drought (AD-23/24) was the most extreme event on record, affecting over 88% of the basin’s area and having a magnitude four times that of the average of the previous top-5 droughts. Notably, the recurrence of high-ranking drought years since 2020 underscores a persistence of extreme conditions in the 2020s. Crucially, the CAED analysis uncovers a distinct temporal regime shift occurring after 2005. While earlier droughts were primarily precipitation-driven, the post-2005 era is characterized by a predominantly evapotranspiration-driven regime, in which climate change-induced warming significantly amplifies drought intensity through increased AED. This intensification is further linked to sea surface temperature anomalies in the Tropical Indian, Tropical Pacific, and North Atlantic oceans. These findings demonstrate that the AB has entered a new hydroclimatic phase in which temperature-driven AED is overtaking precipitation deficits as the primary driver of exceptional drought events. This shift suggests that warming is likely exacerbating drought severity, posing unprecedented challenges for ecosystem stability and water security in the region.

Mozambique’s natural forests are increasingly affected by climate change, deforestation, and unsustainable exploitation, threatening both biodiversity and rural livelihoods. This study examines the wood anatomical characteristics of five commercially important tree species—Spirostachys africana Sond., Afzelia quanzensis Welw., Millettia stuhlmannii Taub., Pterocarpus angolensis DC., and Colophospermum mopane (J. Kirk ex Benth.) J. Léonard—to assess their vulnerability to drought, cyclones, and floods. The aim is to enhance current knowledge regarding their wood anatomy and to clarify how these anatomical traits could help to identify species most vulnerable to climate extremes. Wood samples were collected from native forests and analyzed in laboratories in Brazil and Portugal using standardized anatomical methods according to IAWA guidelines. The results show that Afzelia quanzensis, Millettia stuhlmannii, Pterocarpus angolensis, and Colophospermum mopane have solitary vessels with vestured pits and thick-walled fibers, which improve hydraulic conductivity and drought resistance. Colophospermum mopane shows the greatest anatomical adaptation to climatic stressors. By contrast, Spirostachys africana has narrow, grouped vessels and thin walls, indicating higher susceptibility to embolism and limited resilience. Cyclone resistance is associated with higher wood density and parenchyma abundance, which enhance mechanical stability and recovery. Flood resilience, however, appears to depend more on leaf and root adaptations than on wood anatomy alone. These findings highlight the role of wood structure in climate adaptability and underline the urgency of integrating anatomical data into forest management strategies to support the conservation and sustainable use of Mozambique’s forest resources.

The Mediterranean Basin, renowned for its cultural, ecological, and climatic significance, frequently endures high‐impact weather events driven by Mediterranean cyclones (Medcyclones), atmospheric low‐pressure systems characterized by counterclockwise wind circulation. These meteorological phenomena, sometimes comparable to hurricanes in their intensity and impact, shape the region's weather and are responsible for diverse natural hazards, including torrential rainfall, flash floods, windstorms, and sea surges. Such events have profound and far‐reaching socio‐economic and ecological consequences, particularly for coastal and densely populated areas. Despite their critical role, the systematic assessment of Medcyclones' contribution to socio‐economic losses and the effective communication of associated risks remains limited. This review synthesizes the existing body of knowledge on the socio‐economic impacts of Medcyclones, with a focus on vulnerable sectors such as human health, energy, transportation, agriculture, and cultural heritage. It highlights pressing knowledge gaps, including the need for interdisciplinary research and improved engagement with stakeholders and the public. Advancing the field, this work provides an integrated perspective on Medcyclones' impacts and outlines strategies for resilience, including enhancing predictive models, fostering cross‐sectoral impact studies, and improving disaster preparedness. By bridging the knowledge gaps, this review aims to inform policy‐making and support the development of adaptive measures to mitigate the escalating threats posed by Medcyclones in the context of a changing climate.

Resistance and resilience are usually applied to discuss the functionality of systems, once both describe the responses of biological units to environmental alterations. With this purpose, an analytical methodology focused on the description of functional of vegetation, and their potential correlation with the environmental matrices, was elaborated in the present work. Comparison between amplitudes and averages of morpho-ecological variables, here analyzed by Fluctuation Asymmetries (FAs), was the fundament of this methodology, applied on three different areas of Portugal with similar extensions from north, center, and south Portugal (designed as MB, CP, and FS). The results obtained described very similar functional responses for these study areas. The discussion of these results explained them by high resistance for the three study areas, with lower resilience for one of them (CP), recently exposed to intensive forest fires. So, the functional robustness for these areas will be sustained by their relevant resistance, where environmental variability (geomorphology and climatology) will be the cause of the resilience associated. In this context, increases of the forest production pressions and higher frequencies of fires and climate changes will trigger significant changes in the functionality of their vegetation. Changes in the resilience will be necessary in order to maintain the robustness of vegetation.

During the extended winter period from December 2017 to April 2021, the Iberian Peninsula (IP) was impacted by several high-impact storms characterized by intense precipitation and/or strong winds. This study provides a detailed assessment of the events, including synoptic conditions, large-scale dynamics associated with the storms, and a climatological analysis aimed at improving public understanding and preventing natural disasters. The analysis of the cyclones’ variability indicates that their maximum intensity varies between 955 hPa and 985 hPa, with a duration of two to four days, and the most frequent occurrence (eight events) was in January. At the peak of maximum intensity, the composite anomaly patterns showed lower mean sea level pressure (MSLP) values (−21.6 hPa), higher water vapor values (327.6 kg m−1s−1), and wind speed at 250 hPa exceeding 29.6 m s−1 the mean values. Additionally, there were high anomaly values of equivalent potential temperature (θe) of 19.1 °C at 850 hPa, sea surface temperature (SST) anomaly values of −1 °C, and negative anomaly values of surface latent heat flux (QE) (−150 W m−2) close to the IP. During the days impacted by the storms, the recorded values surpassed the 98th percentile in a significant percentage of days for daily accumulated precipitation (34%), instantaneous wind gusts (46%), wind speed at 10 m (47%), and concurrent events of wind/instantaneous wind gusts and precipitation (26% and 29%, respectively). These findings allow us to describe their meteorological consequences on the IP, particularly the effects resulting from intense precipitation such as floods, and strong winds associated with various destructive impacts. Finally, clear, real-time, and predictive information about weather systems and their impacts is crucial for the public to understand and enable effective responses to mitigate these natural hazards damage.Keywords: extreme events; extratropical cyclones; explosive development cyclones; winter storms; Iberian Peninsula. AcknowledgmentsThis work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC)–UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020), and project WEx-Atlantic (PTDC/CTAMET/29233/2017, LISBOA-01-0145-FEDER-029233, NORTE-01-0145-FEDER-029233). FCT is also providing for Ana Gonçalves doctoral grant (2021.04927.BD). The EPhysLab group was also funded by Xunta de Galicia, Consellería de Cultura, Educación e Universidade, under project ED431C 2021/44 “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas. ReferencesGonçalves, A.C.R.; Nieto, R.; Liberato, M.L.R. Synoptic and Dynamical Characteristics of High-Impact Storms Affecting the Iberian Peninsula during the 2018–2021 Extended Winters. Atmosphere 2023, 14, 1353. https://doi.org/10.3390/atmos14091353

Extreme weather and climate events, such as extratropical cyclones and droughts, represent a topic of paramount importance in the Iberian Peninsula and the North Atlantic Ocean plays an important role in shaping their frequency and intensity. Sea surface temperature (SST) variations, which are important indicators of ocean variability, can result in anomalous diabatic heating or cooling of the overlying atmosphere. In this study, the contributions of different physical processes to the development of North Atlantic explosive extratropical cyclones (EC) affecting the Iberian Peninsula are investigated using the ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). Results suggest that the North Atlantic Ocean SST contributed to the formation and intensification of extratropical cyclones, and particularly to the formation and development of intense storms. Furthermore, the combined analysis of SST and net surface heat flux (QN) also shows the cooling of the ocean associated with the EC tracks caused by the heat exchanges between the ocean and the atmosphere. Acknowledgements This work is supported by national funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020 (https://doi.org/10.54499/UIDB/04033/2020).

The growing increase in frequency and intensity of extreme weather events (EWEs) has a wide impact on energy systems and consumers, such as energy transmission infrastructures - namely overhead power lines (OPL). The main objective of this work is to assess recent high-impact storms and to present the methodology of risk analysis of the extreme weather events on power outages in Portugal. The considered events are windstorms, snowstorms and heavy precipitation associated with extratropical cyclones. In this study, a comprehensive assessment of these events, synoptic conditions and large-scale dynamics are investigated using the ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). Furthermore, the level of risk associated with each of the identified events is classified according to the probability of occurrence and consequences, in a risk matrix, and through the cause-and-effect analysis. It is shown that, in Portugal, the extreme wind – corresponding to level 11 of the Beaufort Wind Force Scale, that is, values equal to or higher than 105 km h-1 – is the main factor that provoked the OPL disruption, between 28% and 40% of analyzed events associated with windstorms. Considering the occurrence of compound events - wind and rain - the probability of damage to OPL is between 21% and 30%; for wind and ice, it is 3%–5%. EWEs represent increasing serious risk for electrical systems, and thus this study highlights the need to develop effective solutions to minimize the associated impacts, such as the modification and upgrade of the current design and engineering standards, and electrical network monitoring. References:Gonçalves, Ana, Margarida Correia Marques, Sílvia Loureiro, Raquel Nieto, and Margarida L.R. Liberato (2023) "Disruption Risk Analysis of the Overhead Power Lines in Portugal", Energy, 263, 125583. https://doi.org/10.1016/j.energy.2022.125583Gonçalves, A.C.R., Nieto R., Liberato M.L.R. (2023) "Synoptic and Dynamical Characteristics of High-Impact Storms Affecting the Iberian Peninsula during the 2018–2021 Extended Winters", Atmosphere, 14, 1353. https://doi.org/10.3390/atmos14091353 Acknowledgements:This work is supported by the Portuguese Science and Technology Foundation through the projects WEx-Atlantic (PTDC/CTAMET/29233/2017, LISBOA-01-0145-FEDER-029233, NORTE-01-0145-FEDER-029233) and UID/GEO/50019/2019. FCT is providing for Ana Gonçalves doctoral grant (2021.04927.BD). This work is supported by national funds by FCT - Portuguese Foundation for Science and Technology, under the project UIDB/04033/2020(https://doi.org/10.54499/UIDB/04033/2020). The EPhysLab group is also funded by Xunta de Galicia, Consellería de Cultura, Educación e Universidade, under project ED431C 2021/44 “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas.