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Millennial-scale climate variations during the last glacial period, such as Dansgaard–Oeschger (DO) cycles and Heinrich events, have been extensively studied using ice core and marine proxy records. However, there is a limited understanding of the magnitude of these temperature fluctuations in continental regions, and questions remain about the seasonal signal of these climate events. This study presents a 60 000-year-long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from lake sediments from the Eifel Volcanic Field, Germany. brGDGTs are bacterial membrane-spanning lipids that are known to have a strong relationship with temperature, making them suitable for temperature reconstructions. We test several temperature calibration models on modern samples taken from soils and multiple maar lakes. We find a negative bias in brGDGT-based temperature estimates associated with water depth and anoxic conditions that can be corrected for by accounting for a brGDGT isomer that is only produced in anoxic conditions. The corrected temperature reconstruction correlates with proxy and climate model estimates of temperature spanning the same time period, validating the calibration approach we selected. However, millennial-scale variability is significantly dampened in the brGDGT record, and in contrast to other Northern Hemisphere climate records, during several Heinrich stadials, temperatures actually increase. We demonstrate that these apparent discrepancies can be explained by the unique seasonal response of the brGDGT paleothermometer to temperatures of months above freezing (TMAF). Our data support the view that warm-season temperatures in Europe varied minimally during the last glacial period and that abrupt millennial-scale events were defined by colder, longer winters. Our continuous high-resolution temperature reconstruction provides important information about the magnitude of seasonal climate variability during the last glacial period that can be used to test climate models and inform studies of paleoecological change. [ABSTRACT FROM AUTHOR]

We find a positive phase of meridional tripole pattern of boreal autumn sea surface temperature anomalies over the tropical and South Pacific (TSPT+) has a synergistic effect with winter negative NAO (NAO−) on the amplitude and occurrence of winter precipitation in southern Europe (SEWP). This synergistic effect is attributed to the linear superposition and nonlinear effect of winter NAO− and preceding autumn TSPT+. The autumn TSPT+ can persist into winter, and the winter TSPT+ with NAO− can stimulate a greater amount of Rossby wave energy propagating to the North Atlantic-Europe (NAE) region than without NAO−, and thereby synergistically regulating circulation with winter NAO−. Thus, winter NAO− and autumn TSPT+ have a synergistic effect on the northwest-southeast trending positive-negative-positive winter circulation over the NAE region. Driven by the intensified mean circulation, water vapor transports and storm activity over southern Europe are evidently strong, which is in favor of SEWP formation. [ABSTRACT FROM AUTHOR]

Relative to drought and heat waves, the effect of winter warming on forest CO2 fluxes during the dormant season has less been investigated, despite its relevance for net CO2 uptake in colder regions with higher carbon content in soils. Our objective was to test the effect of the exceptionally warm winter in 2020 on the winter CO2 budget of cold-adapted evergreen needle-leaf forests across Europe, and identify the contribution of soil and air temperature to changes in winter CO2 fluxes in response to warming. Our hypothesis was that warming in winter leads to higher emissions across colder sites due to increased ecosystem respiration. To test this hypothesis, we used 98 site-year eddy covariance measurements across 14 evergreen needle-leaf forests (ENFs) distributed from north to south of Europe (from Sweden to Italy). We used a data-driven approach to quantify the effect of air and soil temperature on changes in net ecosystem productivity (NEP) during the warm winter of 2020. Our results showed that the impact of warming was different across sites, as in the lower altitude and lower latitude sites positive soil temperature anomalies were larger, while positive air temperature anomalies were larger in the northern latitude and high-altitude sites. Warming in winter led to a divergent response across the sites. Out of 14 sites only in 3 sites net ecosystem productivity declined in winter significantly in response to warming. In addition, we observed that in the colder sites daytime NEP (that is dominated by photosynthesis) declined with warming of the air in winter, whereas in the warmer sites daytime NEP increased with warming of the soil. This shows that warming of the air – if not translated into a direct warming of the soil– might not trigger productivity in winter if the soil within the rooting zone remains frozen. Forests within the same plant functional type category can exhibit differing reactions to winter warming and to predict their responses accurately it is crucial to account for variations in local climate, physiology, and structure simultaneously. [ABSTRACT FROM AUTHOR]

Relative to drought and heat waves, the effect of winter warming on forest CO2 fluxes during the dormant season has less been investigated, despite its relevance for net CO2 uptake in colder regions with higher carbon content in soils. Our objective was to test the effect of the exceptionally warm winter in 2020 on the winter CO2 budget of cold-adapted evergreen needleleaf forests across Europe, and identify the contribution of soil and air temperature to changes in winter CO2 fluxes in response to warming. Our hypothesis was that warming in winter leads to higher emissions across colder sites due to increased ecosystem respiration. To test this hypothesis, we used 98 site-year eddy covariance measurements across 14 evergreen needleleaf forests (ENFs) distributed from north to south of Europe (from Sweden to Italy). We used a data-driven approach to quantify the effect of air and soil temperature on changes in net ecosystem productivity (NEP) during the warm winter of 2020. Our results showed that the impact of warming was different across sites, as in the lower altitude and lower latitude sites positive soil temperature anomalies were larger, while positive air temperature anomalies were larger in the northern latitude and high-altitude sites. Warming in winter led to a divergent response across the sites. Out of 14 sites only in 3 sites net ecosystem productivity declined in winter significantly in response to warming. In addition, we observed that in the colder sites daytime NEP (that is dominated by photosynthesis) declined with warming of the air in winter, whereas in the warmer sites daytime NEP increased with warming of the soil. While warming increases ecosystem respiration, it might not trigger productivity in winter if the soil within the rooting zone remains frozen. Forests within the same plant functional type category can exhibit differing reactions to winter warming and to predict their responses accurately it is crucial to account for variations in local climate, physiology, and structure simultaneously. [ABSTRACT FROM AUTHOR]

Background: Upper respiratory tract infections usually peak during winter months. Objective: The purpose of this study was to evaluate whether imaging of complicated upper airway infection in children increased during the winter season of 2022/2023. Materials and methods: In a retrospective study setting, pediatric magnetic resonance imaging (MRI) and computed tomography (CT) scans for evaluation of upper respiratory tract infection performed between October 2022 and April 2023 were analyzed regarding presence of the following complications: mastoiditis, abscess, phlegmon, meningitis, reactive vasculitis, and sinus vein thrombosis. Pathogen detection, surgery, and infection parameters were obtained. Data were compared with MRI and CT scans performed in the same months of the preceding five years, distinguishing between pandemic and pre-pandemic years. Results: During the 2022/2023 winter season, the number of MRI and CT scans in children with upper airway infections, the complication rate, the rate of detected streptococcal infections, and the rate of surgery increased significantly compared to expectations based on the five prior winter seasons (all P<0.05). During the first complete pandemic winter season in Europe (2020/2021), the number of MRI and CT scans in children with upper airway infection, the complication rate, and the rates of streptococcal detection and surgery decreased significantly compared to expectations based on the pre-pandemic, the second pandemic, and the post-pandemic winter seasons (all P<0.05). Conclusion: After a decline during the first pandemic winter season, there was a marked rebound in complicated upper airway infection in children, with a significant increase in cases during the 2022/2023 winter season compared to the pre-pandemic and pandemic years. [ABSTRACT FROM AUTHOR]

Modern agricultural pest management systems rely on naturally occurring generalist predators to promote pest suppression. Still, little research has been done to assess their overall effectiveness, especially over the winter period when their potential is high. In this study, we focused on three genera of winter-active spiders Clubiona, Philodromus, and Anyphaena, common predators on pear trees in Central Europe during winter and early spring. We investigated their predation activity, natural diet, and prey preference using molecular gut content and abundance data obtained from cardboard bands, which served as natural shelters. We compared these characteristics between two distinct biocontrol-promoting managements—integrated pest management (IPM) and organic management (ORG). We found the proportion of prey-positive spider individuals during the winter period to be lower compared to the spring period with Anyphaena having by far the highest proportion. The prey composition during winter was more diverse in ORG orchards, but in both managements, it was inclined toward pests, mostly pear psyllids. Conversely, in early spring, despite psyllids still being a part of the diet, spiders in IPM orchards preyed more frequently on neutral prey (mostly dipterans), while the spiders from organic orchards preyed mostly on pests (lepidopterans). Although more data are needed to assess trophic interactions and the overall efficiency of these winter-active predators in complex arthropod food webs present in pear orchards, the results obtained from this research provide the first evidence of higher pest predation during a period of agricultural quiescence. [ABSTRACT FROM AUTHOR]

The North Atlantic eddy‐driven jet (EDJ) is the main driver of winter weather in Europe and has often been described by its latitude or strength. Here, we show that the influence of the EDJ on European winter temperature extremes can be better characterized by a multiparametric perspective that accounts for additional aspects of the EDJ structure (tilt, zonal elongation, etc.). We identify four regions where extreme temperatures are distinctly associated with the EDJ: Scandinavia, Central Europe, Eastern Europe, and Western Mediterranean (WMED). Overall, the anomalous horizontal advection induced by blockings during cold spells and enhanced westerlies during warm events is the main mechanism leading to extreme event occurrence. However, diabatic processes play an important role in WMED region. Both processes generate asymmetric effects in minimum and maximum temperatures contributing to higher intensities of cold than warm events. These extreme events are associated with different EDJ configurations, which typically involve perturbed EDJs during cold spells and strong tilted EDJs during warm events, but with important variations depending on the region. In almost every region, the combined effects of more than two EDJ parameters yield significant increases in the probability of cold and warm events, suggesting an oversimplification of traditional approaches based on a single EDJ parameter. We show, using logistic regression models, that, although important, latitude and intensity are often unable to discriminate unequivocally the region of extreme event occurrence, and in some regions, they do not drive the largest changes in the odds of extremes. Plain Language Summary: Weather and climate in Europe are mainly determined by strong winds flowing from the west, also called the North Atlantic jet stream. The jet influences the trajectories of air masses and is related to the occurrence of near surface temperature extreme events. In this work, we analyze the jet configurations associated with winter cold spells and warm events in different regions of Europe by using a decomposition of the jet structure on several parameters, including the intensity, latitude, longitude, tilt, and other zonal asymmetries. We identify four regions with differentiated responses to these jet parameters: Scandinavia, Central Europe, Eastern Europe, and Western Mediterranean. In all cases, the advection of cold and warm air masses is the leading mechanism of temperature extremes. However, this can occur under different jet configurations depending on the type of extreme and its region of occurrence. We show that other EDJ parameters apart from the traditional ones (latitude and intensity) are needed to fully characterize the probability and region of occurrence of temperature extreme events. Key Points: The occurrence of European wintertime temperature extremes can be associated with a combination of a few eddy‐driven jet parametersTypical parameters (latitude and intensity) are not always among the jet features driving the occurrence of extreme temperature eventsSkillful aspects of the jet vary with the type of extreme and region of occurrence [ABSTRACT FROM AUTHOR]

Simple Summary: Ongoing climate change is causing temperatures to rise in both summer and winter, allowing insect pests to invade new areas and potentially causing economic and human health problems. Low winter temperatures are thought to be one of the main barriers to the colonization of higher latitudes. Climate models predict that winter temperatures will increase more than summer temperatures in temperate regions, which may allow insects from warmer regions to colonize the colder, higher latitudes in the future. Understanding how climate change will affect insect distributions is critical for many areas of human activity. This paper presents a method to assess the potential of insects to colonize colder regions under a warming winter scenario. The method is based on exposing insects to laboratory simulations of a warming winter climate. The applicability of the method is tested using the example of a Mediterranean pest, Sesamia nonagrioides, whose ability to colonize Central Europe is assessed. The results indicate that S. nonagrioides could survive Central European winters even under the current state of warming or under a warmer climate predicted for the near future. The presented method may be particularly useful in pest management to estimate overwinter survival and distribution of pests due to climate change. Ongoing climate change and anthropogenic pressure are having a profound influence on insects, causing species diversity to decline and populations to shrink. Insect pests invade new areas and cause economic and human health problems. Low temperatures in winter are thought to be one of the main barriers to the successful colonization of higher latitudes. Climate models predict that winter temperatures will increase more than summer temperatures in temperate and polar regions, potentially allowing species from warmer climates to colonize higher latitudes. Understanding how climate change will affect the distribution of insects is critical to many areas of human activity. One possible but seldom used way to predict likely range shifts of insects due to climate change is through simulation experiments. Here, I present and test a method to assess the potential of insect species from warmer regions to survive winters in colder regions under a warming winter scenario. The method is based on laboratory simulations of warming winters. The applicability of the method is demonstrated using the example of a Mediterranean pest, Sesamia nonagrioides, whose ability to survive Central European winters under a warming winter scenario is assessed. The method presented here is relatively simple, with potentially high accuracy of estimates. [ABSTRACT FROM AUTHOR]

Weather regimes are recurrent and quasi‐stationary large‐scale atmospheric circulation patterns, typically linking to surface weather. Two commonly used sets of weather regimes are wintertime North American and Euro‐Atlantic regimes. Notwithstanding recent evidence pointing to a connection between winter weather in North America and Europe, there is little knowledge on the possible relation between North American and Euro‐Atlantic regimes. Here, we find that specific pairs of North American and Euro‐Atlantic regimes show a close visual and statistical correspondence. Moreover, the joint analysis of the two sets of regimes can provide medium‐range statistical predictability for anomalies in their occurrence frequencies. Conditioning on North American weather regimes also results in anomalies in both the large‐scale circulation during specific Euro‐Atlantic regimes, and the associated European surface weather. We conclude that there is a benefit in conducting joint analyses of North American and European weather regimes, as opposed to considering the two in isolation. Plain Language Summary: Wintertime weather in Europe is closely related to large‐scale atmospheric patterns occurring over scales of thousands of kilometers. These patterns, termed weather regimes, are relatively persistent in time, and occur repeatedly. Such weather regimes have been used for many applications, including predicting the weather several weeks in advance. Weather regimes conceptually similar to those identified for Europe have also been determined for North America. In this study, we look at whether and how North American and European weather regimes are related. We show that the two sets of weather regimes have a statistical link, and that accounting for North American regimes can help to gain a more detailed understanding of how European regimes relate to weather in Europe. Key Points: Specific pairs of North American and Euro‐Atlantic weather regimes show a close relationA joint analysis of the two sets of regimes can provide statistical predictability for anomalies in their occurrence frequenciesNorth American regimes have a clear footprint on the European surface weather associated with Euro‐Atlantic regimes [ABSTRACT FROM AUTHOR]

Central European winters have warmed markedly since the mid-20th century. Yet cold winters are still associated with severe societal impacts on energy systems, infrastructure and public health. It is therefore crucial to anticipate storylines of worst-case cold winter conditions, and to understand whether an extremely cold winter, such as the coldest winter in the historical record of Germany in 1963 (−6.3 °C or −3.4 σ seasonal DJF temperature anomaly relative to 1981–2010), is still possible in a warming climate. Here, we first show based on multiple attribution methods that a winter of similar circulation conditions to 1963 would still lead to an extreme seasonal cold anomaly of about −4.9 to −4.7 °C (best estimates across methods) under present-day climate. This would rank as second-coldest winter in the last 75 years. Second, we conceive storylines of worst-case cold winter conditions based on two independent rare event sampling methods (climate model boosting and empirical importance sampling): winter as cold as 1963 is still physically possible in Central Europe today, albeit very unlikely. While cold winter hazards become less frequent and less intense in a warming climate overall, it remains crucial to anticipate the possibility of an extreme cold winter to avoid potential maladaptation and increased vulnerability. [ABSTRACT FROM AUTHOR]

Aim: Temperature is the main driver of growth reactivation in plants of extratropical regions. Accumulations of chilling and forcing units during dormancy co‐regulate spring phenology. Here, we aimed to answer whether chilling and forcing proceed in parallel or sequentially to regulate spring phenology in temperate trees. Location: Europe. Time Period: 1951–2016. Major Taxa Studied: Nine temperate woody species. Methods: Using long‐term and large‐scale records of in situ leaf unfolding dates of temperate tree species at more than 2300 sites, we analysed the rolling partial correlations between leaf unfolding dates and chilling and forcing in winter and spring using a weekly smoothing window. Through process‐based modelling, we further identified the start of forcing accumulation and the end of chilling accumulation using the Unified model and compared the model efficiency of the Parallel and the Sequential models. Results: We observed negative responses of leaf unfolding dates to accumulations of both chilling and forcing units for most of winter and spring across successional types of species (early‐ and late‐successional taxa), elevations and periods. Using the Unified model, we also found overlapping windows for chilling and forcing accumulations. Moreover, the Parallel model performed better than the Sequential model. These findings suggested that chilling and forcing requirements may be fulfilled simultaneously in temperate trees. Main Conclusions: Our study not only provides a guideline for identifying the effective periods of chilling and forcing, but also a general and robust perspective that accumulations of chilling and forcing act in parallel to regulate spring leaf unfolding in temperate trees, promoting more precise and reasonable predictions of temperature‐driven phenological shifts under future climate change. [ABSTRACT FROM AUTHOR]

Millennial-scale climate variations during the last glacial period, such as Dansgaard–Oeschger (D/O) cycles and Heinrich events, have been extensively studied using ice core and marine proxy records. However, there is a limited understanding of the magnitude of these temperature fluctuations in continental regions, and questions remain about the seasonal signal of these climate events. This study presents a 60,000-year long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from lake sediments from the Eifel volcanic field, Germany. brGDGTs are bacterial membrane lipids that are known to have strong relationship with temperature, making them suitable for temperature reconstructions. We test several temperature calibration models on modern samples taken from soils and multiple maar lakes. We find a bias associated with water depth and anoxic conditions that can be corrected for by accounting for a brGDGT isomer that is only produced in anoxic conditions. The corrected temperature reconstruction correlates with proxy and model temperature record spanning the same time period, validating the calibration model. However, millennial-scale variability is significantly dampened in the brGDGT record, and in contrast to other northern hemisphere climate records, during several Heinrich stadials, temperatures actually increase. We demonstrate that these apparent discrepancies can be explained by the unique seasonal response of the brGDGT paleothermometer to temperatures of months above freezing (TMAF). Our data support the view that warm season temperatures in Europe varied minimally during the last glacial period, and that abrupt millennial-scale events were defined by colder, longer winters. Our continuous high-resolution temperature reconstruction provides important information about the magnitude of seasonal climate variability during the last glacial period that can be used to test climate models and inform studies of paleoecological change. [ABSTRACT FROM AUTHOR]

Wintertime extremes such as cold spells and heavy precipitation can have severe socioeconomic impacts, disrupting critical infrastructures and affecting human well-being. Here, we relate the occurrence of local and concurrent cold or wet wintertime extremes in North America and Europe to a recurrent, quasi-hemispheric wave-4 Rossby wave pattern. We identify this pattern as a fundamental mode of the Northern Hemisphere (NH) winter circulation, since wave 4 exhibits phase-locking behavior. Thus, the associated atmospheric circulation and surface anomalies reoccur over the same locations when the pattern's wave amplitude is high. The wave pattern is most pronounced over the pan-Atlantic region, and increases the probability of extreme cold or wet events by up to 300% in certain areas of North America and Europe, as well as favoring their concurrence at different locations. High-amplitude wave-4 events have increased significantly in frequency over the past four decades (1979-2021), although no clear evidence is found relating this to modes or patterns of climate variability. The identified wave pattern may provide pathways for early prediction of local and concurrent cold or wet wintertime extremes in North America and Europe. [ABSTRACT FROM AUTHOR]

The Thirty Years' War, which took place from 1618 to 1648 CE, was an armed military conflict in Europe. It resulted from the culmination of theological differences between advocates of the Roman Catholic and Protestant churches, as well as a power struggle for European political hegemony. This war brought about extensive devastation to Europe. Based on documentary evidence, this paper characterizes the climate, weather extremes, and economic and socio-political events in central Europe during that time. Natural climate forcing indicates a gradual climate deterioration during the first half of the 17th century, associated with a decrease in solar activity towards the Maunder Minimum and increased volcanic activity. The mean temperatures in central Europe from 1618 to 1648 were significantly colder than the reference period of 1961 to 1990 in winter, autumn, and annually, while precipitation and drought means did not differ significantly from the reference period. Summer temperatures, spring precipitation, and drought also exhibited significantly greater variability. As for weather extremes, particularly late winter, late spring and early autumn frosts, floods, intense rain spells, and droughts affected grain, fruit, and vine grape harvests, as well as the yields of other crops. These weather extremes contributed to various human impacts, such as food shortages (reflecting harvests and grain prices), famines, and epidemics. Ultimately, these events, along with the effects of the war, led to a decline in the population. The results obtained are discussed within the broader European context, taking into account climate, weather extremes, and socio-economic impacts. [ABSTRACT FROM AUTHOR]

During the winters of the 2020–2022 period, several intense North African dust intrusions affected Europe. Some of them displayed a duration never recorded before. They were referred to as exceptional by several international operational and research institutions considering that wintertime is the season with minimum dust activity in the Mediterranean and Europe. These anomalous winter events with origin in North Africa largely affected western Mediterranean. The main objective of the present work is to analyse the atmospheric drivers (synoptic and large-scale environments) of wintertime (from January to March) dust events over the region covering North Africa, the Western Mediterranean and the Euro-Atlantic during the period 2003–2022. Overall, our results indicate large interannual variability over the study period. A dust catalogue of dust events identified by aerosols retrievals from satellite and aerosol reanalysis products shows a very irregular record and large differences between winter months. The analyses demonstrate a positive anomaly in dust concentration and maximum altitude during the dust events of 2020–2022 in comparison with those of previous years (2003–2019). Winter dust events over western Mediterranean are associated with enhanced blocking activity over the Euro-Atlantic sector, which favours the obstruction of the westerlies and the occurrence of cut-off lows at subtropical latitudes. However, these high-pressure systems can exhibit a large variety of configurations, including meridional dipole blocking patterns with poleward shifted jets or Mediterranean subtropical ridges with an intensified mid-latitude jet. The former was more frequent during the reference 2003–2019 period, whereas the latter was relatively common during the anomalous 2020–2022 period. [ABSTRACT FROM AUTHOR]

North Atlantic Oscillation (NAO) has a significant impact on surrounding winter weather and climate. However, the causes of its occasional reversal between early and late winter remain unclear. This study proposes a mechanism for the mid‐winter reversal of NAO from the perspective of local midlatitude air‐sea interaction. Strong sea surface temperature (SST) tripole events, which are defined by empirical orthogonal function of winter‐mean interannual North Atlantic SST anomalies, are primarily induced by NAO in early winter and peak in January. In late winter, the persistent SST tripole exerts active feedback on atmosphere through diabatic heat and transient eddy forcing. The resulting atmospheric circulation anomalies exhibit an almost reversed NAO pattern in February, which forms a wavetrain originating above the Gulf Stream and propagating to the Middle East and weakens the former SST tripole. Consequently, significant reversals of air temperature anomalies occur in Europe and the Caspian Sea area between February and December. Plain Language Summary: The North Atlantic Oscillation (NAO) is a crucial atmospheric system that significantly impacts the weather and climate of the surrounding regions during winter. However, it often reverses between early and late winter, and the reasons for its mid‐winter reversal remain unclear. The NAO behavior can be influenced by multiple factors, such as atmospheric internal processes, underlying surface, and remote climate system, which makes the issue more complex. This study highlights the role of underlying sea surface temperature anomalies (SSTAs) in the mid‐winter reversal of NAO. The North Atlantic SSTAs are closely associated with the NAO and exhibit a tripole pattern. For strong sea surface temperature (SST) tripole events, the NAO primarily induces the early winter North Atlantic SST tripole. The SSTAs develop in early winter, peak in January, and feedback on the atmospheric circulation in late winter. The atmospheric circulation anomalies exhibit an almost reversed NAO pattern in February, forming a wavetrain that propagates above the Gulf Stream to the Middle East. As a result, during the warm phase of the SST tripole, Europe experiences colder temperatures, and the Caspian Sea experiences warmer temperatures in February than usual, as opposed to the positive NAO's control over warm Europe and cold Caspian Sea in December. Key Points: In early winter, North Atlantic Oscillation (NAO) forces a North Atlantic sea surface temperature (SST) tripole, which persists and tends to induce a nearly reversed NAO pattern in FebruarySST tripole induces a wavetrain over the Gulf Stream to the Middle East via diabatic heating and transient eddy forcing in FebruaryAs a result, there are remarkable reversals of air temperature anomalies in Europe and Caspian Sea area between February and December [ABSTRACT FROM AUTHOR]

According to Gloger's rule, animal colouration is expected to be darker in wetter and warmer climates. Such environmental clines are predicted to occur in colour polymorphic species and to be shaped by selection if colour morphs represent adaptations to different environments. We studied if the distribution of the colour polymorphic tawny owl (Strix aluco) morphs (a pheomelanic brown and a pale grey) across Europe follow the predictions of Gloger's rule and if there is a temporal change in the geographical patterns corresponding to regional variations in climate change. We used data on tawny owl museum skin specimen collections. First, we investigated long‐term spatiotemporal variation in the probability of observing the colour morphs in different climate zones. Second, we studied if the probability of observing the colour morphs was associated with general climatic conditions. Third, we studied if weather fluctuations prior to the finding year of an owl explain colour morph in each climate zone. The brown tawny owl morph was historically more common than the grey morph in every studied climate zone. Over time, the brown morph has become rarer in the temperate and Mediterranean zone, whereas it has first become rarer but then again more common in the boreal zone. Based on general climatic conditions, winter and summer temperatures were positively and negatively associated with the proportion of brown morph, respectively. Winter precipitation was negatively associated with the proportion of brown morph. The effects of 5‐year means of weather on the probability to observe a brown morph differed between climate zones, indicating region‐dependent effect of climate change and weather on tawny owl colouration. To conclude, tawny owl colouration does not explicitly follow Gloger's rule, implying a time and space‐dependent complex system shaped by many factors. We provide novel insights into how the geographic distribution of pheomelanin‐based colour polymorphism is changing. [ABSTRACT FROM AUTHOR]

Simple Summary: The phenology of avian migration adjusts to rapid changes in the climate in Europe. The North Atlantic Oscillation (NAO), which reflects weather patterns in western Europe, has been demonstrated to influence the timing of bird migration. The question is, how does climate in other regions of their wintering and breeding grounds in Europe influence migrants, which move between these areas? We aimed to determine carry-over effects of the Mediterranean Oscillation Index (MOI), a proxy for non-breeding conditions in the eastern Mediterranean, and the Scandinavian Pattern (SCAND), which reflects conditions at the breeding grounds, in combination with NAO, on the timing of the European wren's short-distance spring migration through the Baltic Sea coast over 1982–2021. We showed that a combination of winter and spring MOI and NAO, as well as SCAND from the previous breeding season, explained the year-to-year variation in timing of the wren's spring passage at the Baltic coast three to ten months later. Our study reveals that conditions the migrants encounter at wide non-breeding and breeding grounds during the preceding year have a carry-over effect on spring phenology of migrants in Europe, while spring conditions just fine-tune their timing. Many studies have linked changes in avian phenology in Europe to the North Atlantic Oscillation (NAO), which serves as a proxy for conditions in western Europe. However, the effects of climate variation in other regions of Europe on the phenology of short-distance migrants with large non-breeding grounds remain unclear. We determined the combined influence of large-scale climate indices, NAO, the Mediterranean Oscillation Index (MOI), and the Scandinavian Pattern (SCAND), during the preceding year on spring migration timing of European wren at the southern Baltic coast during 1982–2021. We modelled the effects of these climate variables on the entire passage and subsequent percentiles of the wren's passage at Bukowo-Kopań and Hel ringing stations. Over 1982–2021, the start and median of migration shifted earlier at Hel, but the end of passage shifted later at both stations. In effect, the duration of passage at Hel was extended by 7.6 days. Early passage at Hel was related with high MOI in spring and the preceding autumn. Spring passage at Bukowo-Kopań was delayed after high NAO in the previous breeding season, and high winter and spring NAO. Late spring passage occurred at both stations following a high SCAND in the previous summer. At both locations, an early start or median of passage followed high local temperatures. We conclude that phenology of the wren's spring migration at the Baltic coast was shaped by conditions encountered at wintering quarters in western Europe, where NAO operates, and in the south-eastern Europe, where the MOI operates, in conjunction with conditions in Scandinavia during the previous breeding season. We demonstrated that climate variability in various parts of the migrants' range has combined carry-over effects on in migrants' phenology in Europe. [ABSTRACT FROM AUTHOR]

The impact of factors such as density dependence, food availability and weather are known to be important for predicting population change in a wide range of species. However, a challenge in ecology is understanding the contributory and interactive role of these drivers on populations. This is necessary to design effective conservation and management strategies. Using data from long‐term studies of five hazel dormouse Muscardinus avellanarius populations in Europe, we tested the relationship between population density and weather and their impact on demographic rates. We used an integrated population modelling approach, estimating age‐specific overwinter survival, annual population growth and fecundity rates. We found strong negative effects of population density, precipitation and winter temperature on population growth rates. This suggests that warmer and wetter weather negatively affects dormouse survival for both adults and juveniles, but we found subtle differences in these effects between age classes. We also identified an interaction between weather measures and population density on age‐specific survival, possibly as a result of weather impacts during hibernation. Although we found low winter temperature was positively associated with population growth, we found evidence consistent with density dependence. We discuss our results in the context of woodland habitat conservation management. [ABSTRACT FROM AUTHOR]

While two-rowed barley is usually preferred for malting and beer-making, six-rowed malting barley varieties appeared in Europe around 30 years ago, and several breeders have dedicated improvement programs on this specific germplasm. In this study, we evaluated the feasibility of genomic prediction for yield and malting related traits using 679 breeding lines from two French barley breeders, as well as a set of recently registered varieties. These lines were evaluated in five locations and two harvest years in an unbalanced design. Although the germplasm from the two breeders does show some trend towards differentiation, globally the whole panel did not show a clear-cut genetic structure. Predictive ability of GBLUP was evaluated through random cross-validation within and across breeder sets, and using cross-prediction between breeder sets. Results show moderate to high predictive ability (PA), particularly for malt friability and β-glucan content, for which predictive ability of 0.8 was obtained with training populations as small as 105 registered varieties and across breeding sets. The long range of useful linkage disequilibrium in this particular germplasm allows using as few as 2000 to 5000 markers to obtain high PA. Other prediction methods such as Bayesian LASSO, Bayes Cpi or EGBLUP did not improve predictive ability. These results are very encouraging for implementing genomic prediction of malting quality traits in applied breeding programs. [ABSTRACT FROM AUTHOR]

Midlatitude atmospheric blocking events are important drivers of long-lasting extreme weather conditions at regional to continental scales. However, modern climate models consistently underestimate their frequency of occurrence compared to observations, casting doubt on future projections of climate extremes. Using the prominent and largely underestimated winter blocking events in Europe as a test case, this study first introduces a spatio-temporal approach to study blocking activity based on a clustering technique, allowing to assess models' ability to simulate both realistic frequencies and locations of blocking events. A sensitivity analysis from an ensemble of 49 simulations from 24 coupled climate models shows that the presence of a mesoscale eddy-permitting ocean model increases the realism of simulated blocking events for almost all types of patterns clustered from observations. This finding is further explained and supported by concomitant reductions in well-documented biases in Gulf Stream and North Atlantic Current positions, as well as in the midlatitude jet stream variability. [ABSTRACT FROM AUTHOR]

Shipping contributes significantly to air pollutant emissions and atmospheric particulate matter (PM) concentrations. At the same time worldwide maritime transport volumes are expected to continue to rise in the future. The Mediterranean Sea is a major short-sea shipping route within Europe, as well as the main shipping route between Europe and East Asia. As a result, it is a heavily trafficked shipping area, and air quality monitoring stations in numerous cities along the Mediterranean coast have detected high levels of air pollutants originating from shipping emissions. The current study is a part of the EU Horizon 2020 project SCIPPER (Shipping contribution to Inland Pollution - Push for the Enforcement of Regulations) which intends to investigate how existing restrictions on shipping-related emissions to the atmosphere ensure compliance with legislation. To demonstrate the impact of ships on relatively large scales, the potential shipping impacts on various air pollutants can be simulated with chemistry transport models. To determine formation, transport, chemical transformation and fate of PM2.5 in the Mediterranean Sea in 2015, five different regional chemistry transport models (CAMx – Comprehensive Air Quality Model with Extensions, CHIMERE, CMAQ – Community Multiscale Air Quality model, EMEP – European Monitoring and Evaluation Programme model, LOTOS-EUROS) were applied. Furthermore, PM2.5 precursors (NH3, SO2, HNO3) and inorganic particle species (SO42−, NH4+, NO3−) were studied, as they are important for explaining differences among the models. STEAM version 3.3.0 was used to compute shipping emissions, and the CAMS-REG v2.2.1 dataset was used to calculate land-based emissions for an area encompassing the Mediterranean Sea at a resolution of 12 × 12 km2 (or 0.1° × 0.1°). For additional input, like meteorological fields and boundary conditions, all models utilized their regular configuration. The zero-out approach was used to quantify the potential impact of ship emissions on PM2.5 concentrations. The model results were compared to observed background data from monitoring sites. Four of the five models underestimated the actual measured PM2.5 concentrations. These underestimations are linked to model-specific mechanisms or underpredictions of particle precursors. The potential impact of ships on the PM2.5 concentration is between 15 % and 25 % at the main shipping routes. Regarding particle species, SO42− is main contributor to the absolute ship-related PM2.5 and also to total PM2.5 concentrations. In the ship-related PM2.5, a higher share of inorganic particle species can be found when compared to the total PM2.5. The seasonal variabilities in particle species show that NO3− is higher in winter and spring, while the NH4+ concentrations displayed no clear seasonal pattern in any models. In most cases with high concentrations of both NH4+ and NO3−, lower SO42− concentrations are simulated. Differences among the simulated particle species distributions might be traced back to the aerosol size distribution and how models distribute among the coarse and fine mode (PM2.5 and PM10). The seasonality of wet deposition follows the seasonality of the precipitation, displaying that precipitation predominates the wet deposition. [ABSTRACT FROM AUTHOR]

Poppy cultivation has a long tradition in Central Europe. Growing winter poppy instead of the commonly grown spring poppy might increase seed yield, especially in the face of changing climatic conditions. However, knowledge regarding optimum sowing date and optimum sowing rate for winter poppy under Pannonian climate conditions in Central Europe is missing. Therefore, a two-year field experiment was performed in Eastern Austria with four sowing dates ranging from early September to mid/end of October and two sowing rates with 50 or 100 mg seeds m−2. Seed yields were considerably higher than values reported for spring poppy throughout all sowing dates, mainly due to a higher number of seeds capsule−1 and, thereby, a higher seed yield capsule−1. The highest seed yields were obtained by sowing in early October, while the earliest and especially the latest sowing date resulted in lower seed yields. Consequently, the optimum sowing date for winter poppy under Pannonian climate conditions in Central Europe is early October but sowing can be performed over a wider range of dates. No seed yield differences were observed between sowing rates. Consequently, the sowing rate can be much lower than the recommended sowing rate for spring poppy. [ABSTRACT FROM AUTHOR]

Hibernation is one of the most important behaviours of bats of the temperate zone. During winter, when little food or liquid water is available, hibernation in torpor lowers metabolic costs. However, the timing of emergence from hibernation is crucial for the resumption of the reproductive process in spring. Here, we investigate the spring emergence of six bat species or pairs of bat species of the genera Myotis and Plecotus at five hibernation sites in Central Europe over 5 years. Using generalized additive Poisson models (GAPMs), we analyze the influence of weather conditions (air and soil temperature, atmospheric pressure, atmospheric pressure trend, rain, wind, and cloud cover) as predictors of bat activity and separate these extrinsic triggers from residual motivation to emerge from hibernation (extrinsic factors not studied; intrinsic motivation). Although bats in a subterranean hibernaculum are more or less cut off from the outside world, all species showed weather dependence, albeit to varying degrees, with air temperature outside the hibernaculum having a significant positive effect in all species. The residual, potentially intrinsic motivation of species to emerge from their hibernacula corresponds to their general ecological adaptation, such as trophic specialization and roosting preferences. It allows the definition of three functional groups (high, medium and low residual activity groups) according to the degree of weather dependence of spring activity. A better knowledge of the interplay of extrinsic triggers and residual motivation (e.g., internal zeitgebers) for spring emergence will help to understand the flexibility of a species to adapt to a changing world. [ABSTRACT FROM AUTHOR]

Ural blocking (UB) is a prominent mode of variability of the Northern Hemisphere atmospheric circulation, particularly in fall. It can persist for several days and exert a lagged influence on the wintertime NH circulation, providing predictability at the subseasonal time scale. Using two atmospheric models, we explore how the early winter atmospheric circulation responds to a 2‐week persistent UB anomaly imposed in early November. Experiments are carried out with two different configurations of Barents‐Kara (BK) sea‐ice concentration to examine whether it plays a role in how UB impacts atmospheric variability. In both models, the UB anomaly is followed by a weakening of the stratospheric polar vortex and a negative phase of the North Atlantic Oscillation (NAO), which lasts up to 2 months after the forcing is released. Interestingly, the response is more persistent under low BK sea‐ice conditions, that is, BK sea ice modulates the atmospheric response to UB. Additional experiments with prescribed sea ice concentration anomalies alone suggest that BK sea ice exerts a limited influence on early winter NH atmospheric variability. The response to UB involves a weakening of the polar vortex that persists longer under low BK sea ice, which explains the more persistent response in that configuration. Our study highlights that UB variability in November is a robust precursor for early winter NAO/polar stratosphere anomalies, and this may be more relevant in the context of declining Arctic sea‐ice extent. Provided that climate models accurately capture this teleconnection, it has the potential to improve subseasonal predictions of the NH wintertime climate. Plain Language Summary: Predicting subseasonal fluctuations of the polar stratosphere in winter (or polar vortex) is critical to anticipate weather extreme events over populated areas of the Northern Hemisphere. In this study, we highlight that a persisting high‐pressure system over the Europe/Ural region in fall (known as Ural blocking [UB]) can force a delayed response at the surface several weeks later, that resembles the negative phase of the North Atlantic Oscillation (NAO). This is found in two different atmospheric models in which the UB pattern is imposed during the first 2 weeks of November, using a regional relaxation of the troposphere. We also investigate the response to fall/early winter Barents‐Kara sea ice decline, which has been hypothesized to have a similar impact on the polar vortex/NAO, but we find that it is of secondary importance compared to the influence of UB. Key Points: Two‐week persistent Ural blocking (UB) anomalies induce a weaker polar vortex and negative North Atlantic OscillationRole of Barents‐Kara (BK) sea ice is secondary compared to the influence of UBHowever, BK sea ice modulates the persistence of the response to UB [ABSTRACT FROM AUTHOR]

Aerosols can strongly influence atmospheric circulation, and categorizing it into circulation types (CTs) helps in understanding the relationship between atmospheric forcing and surface conditions. However, few studies have considered the impact of interactive aerosols on atmospheric dynamics from a climatic perspective. This contribution aims to assess whether simulations with interactive aerosols (online solving of aerosol–radiation interactions, ARI, and aerosol–radiation–cloud interactions, ARCI) significantly impact atmospheric dynamics over Europe during winter compared to conventional regional climate models with prescribed aerosols. For that, Principal Component Analysis (PCA) has been applied to reduce the dimensionality of the problem in order to cluster different weather patterns. Results showed significant differences in the two predominant patterns, characterized by a western zonal flow (CT1) and a low-pressure system centered in Italy (CT2). The ARI experiment revealed a substantial reduction of surface level pressure over central-eastern Europe for CT1, resulting in a southward shift of the flux direction, and an increase in pressure over Scandinavia for CT2. The ARCI experiment exhibited a similar, but weaker effect. Furthermore, the study demonstrated the impact of aerosols on the frequency of different CTs and on the concentration of black and white aerosols. The findings of this study emphasize the significant role of aerosols in the atmospheric system and the need for further research to reduce uncertainty in meteorological and climatic experiments, particularly in the context of mitigating climate change. [ABSTRACT FROM AUTHOR]

Condensation trails (contrails) from aircraft exhausts and contrail cirrus clouds play a significant role in the atmosphere's radiation balance and the climate. The aim of this study is to analyse the physical properties of contrails with the use of satellite data and determine the atmospheric conditions favoring their formation and persistence. The contrails are detected on satellite images provided by the Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) radiometer onboard the Meteosat Second Generation (MSG) satellites, using a modified version of the contrail detection algorithm by Mannstein et al. Int J Remote Sens 20(8):1641–1660. (1999) for the year 2016. The study area covers central and western Europe. Five contrail detection hotspots are located, with contrail density depending on time of day and season. The length of the detected contrails ranges between 225 and 292.5 km and the mean width between 5.1 and 8.1 km. The spatial contrail cover reaches up to 0.085% of the scene, with larger values being detected between 8 and 10 UTC and during winter. Results of the comparison with the ERA-5 reanalysis database show that contrail formation and persistence is favored in ice saturated areas (RHI≈100%), when the air temperature is between 204 and 232 Κ (− 69.2 to − 41.2 °C) and the specific humidity between 0.025 and 0.0625 g/kg. The favorable wind direction and speed lie between W and SW (240–300°) and 10 and 30 m/s, respectively. [ABSTRACT FROM AUTHOR]

The North Atlantic Oscillation ("NAO") and the East Atlantic Pattern ("EAP") dominate winter atmospheric variability over the North Atlantic. Unlike the NAO, seasonal predictability of the EAP has remained elusive. A multi‐model ensemble of seasonal predictions yields skillful forecasts of the EAP in late autumn and early winter, complementing NAO prediction skill in winter. The shift in prediction skill from EAP to NAO reflects the ability of the ensemble to forecast the evolving influence of the El Niño South Oscillation on the North Atlantic region. In early winter, the ensemble correctly forecasts the key tropical–extratropical teleconnections, resulting in skillful predictions of the EAP and western European temperatures and rainfall. However, the modeled tropical–extratropical teleconnections are weak compared to observations, contributing to a signal to noise error in predictions of the EAP. Improving the strength of such teleconnections would improve predictions of the EAP and associated surface climate. Plain Language Summary: Predicting the most likely weather patterns ahead of the autumn and winter can be very useful for resilience planning. To date, skillful forecasts have only been possible for the most common pattern of winter atmospheric variability over the North Atlantic and European region, called the North Atlantic Oscillation ("NAO"), with no significant skill for the second pattern, called the East Atlantic Pattern ("EAP"). Using seasonal predictions from a range of coupled ocean—atmosphere models, we demonstrate significant skill in the EAP, in late autumn and early winter. The associated temperature and precipitation variability across western Europe is also skilfully predicted. We further show that skill shifts from the EAP to the NAO over the autumn to winter and reflects the evolving influence of the El Niño South Oscillation, a large‐scale atmosphere‐ocean feature of the tropical Pacific. However, climate models underestimate the magnitude of the predictable signal of the EAP, as found previously for the NAO. Resolving this error would further improve seasonal predictions of the late autumn and early winter period. Key Points: Seasonal prediction skill of the East Atlantic Pattern and associated surface climate is demonstrated in late autumn and early winterA seasonal shift in prediction skill reflects the evolving influence of the El Niño Southern Oscillation on the North Atlantic regionModeled tropical–extratropical teleconnections are weak, contributing to a signal to noise error in East Atlantic Pattern predictions [ABSTRACT FROM AUTHOR]

The low-temperature algal biotechnology starts to develop in the Polar Regions, and especially in the Arctic. Light is crucial environmental factor in algal mass cultivation, therefore knowledge of the light environment and its modeling is crucial for design of the photobioreactors. The light conditions in three different environments were compared: natural diel light cycle during the polar summer (June-August) in Svalbard and in winter/spring (January - March) in the Central Europe outdoor and in the greenhouse photobioreactor, and in greenhouse photobioreactor equipped by additional night LED illumination in central Europe in winter/spring. In Svalbard, the monthly mean diel PAR values ranger from 126 to 395 µmol m-2 s-1, and the monthly diel sums of the PAR ranged from 2.38 to 7.47 MJ m-2 d-1. In the Central Europe in natural diel light cycle, the monthly mean diel PAR values and monthly diel sums of the PAR were generally lower, 57 - 248 µmol m-2 s-1 and 1.08 and 4.69 MJ m-2 d-1 in outdoor and 26 - 107 µmol m-2 s-1 and 0.50 - 2.03 69 MJ m-2 d-1 in the sun-illuminated photobioreactor. When additional night LED illumination, lasting from 12 to 14.7 hrs and from 12 to 15.3 hrs in 2021 and 2022, respectively, was provided, the monthly mean diel PAR values and monthly diel sums of the PAR increased to 479 - 598 µmol m-2 s-1 and 9.06 - 11.31 MJ m-2 d-1, respectively. Since the Svalbard maxima of diel sum of PAR are comparable to the values found in the night LED illuminated greenhouse photobioreactor, the night LED illumination in winter/spring in Central Europe should be proposed for model cultivations in the Polar Region in summer. [ABSTRACT FROM AUTHOR]

Context: Soaring birds depend on atmospheric uplifts and are sensitive to wind energy development. Predictive modelling is instrumental to forecast conflicts between human infrastructures and single species of concern. However, as multiple species often coexist in the same area, we need to overcome the limitations of single species approaches. Objectives: We investigate whether predictive models of flight behaviour can be transferred across species boundaries. Methods: We analysed movement data from 57 white storks, Ciconia ciconia, and 27 griffon vultures, Gyps fulvus. We quantified the accuracy of topographic features, correlates of collision risk in soaring birds, in predicting their soaring behaviour, and tested the transferability of the resulting suitability models across species. Results: 59.9% of the total area was predicted to be suitable to vultures only, and 1.2% exclusively to storks. Only 20.5% of the study area was suitable to both species to soar, suggesting the existence of species-specific requirements in the use of the landscape for soaring. Topography alone could accurately predict 75% of the soaring opportunities available to storks across Europe, but was less efficient for vultures (63%). While storks relied on uplift occurrence, vultures relied on uplift quality, needing stronger uplifts to support their higher body mass and wing loading. Conclusions: Energy landscapes are species-specific and more knowledge is required to accurately predict the behaviour of highly specialised soaring species, such as vultures. Our models provide a base to explore the effects of landscape changes on the flight behaviour of different soaring species. Our results suggest that there is no reliable and responsible way to shortcut risk assessment in areas where multiple species might be at risk by anthropogenic structures. [ABSTRACT FROM AUTHOR]

The winter 1788/89 was one of the coldest winters Europe had witnessed in the past 300 years. Fortunately, for historical climatologists, this extreme event occurred at a time when many stations across Europe, both private and as part of coordinated networks, were making quantitative observations of the weather. This means that several dozen early instrumental series are available to carry out an in-depth study of this severe cold spell. While there have been attempts to present daily spatial information for this winter, there is more to be done to understand the weather variability and day-to-day processes that characterised this weather extreme. In this study, we seek to reconstruct daily spatial high-resolution temperature and sea level pressure fields of the winter 1788/89 in Europe from November through February. The reconstruction is performed with an analogue resampling method (ARM) that uses both historical instrumental data and a weather type classification. Analogue reconstructions are then post-processed through an ensemble Kalman fitting (EnKF) technique. Validation experiments show good skill for both reconstructed variables, which manage to capture the dynamics of the extreme in relation to the large-scale circulation. These results are promising for more such studies to be undertaken, focusing on different extreme events and other regions in Europe and perhaps even further back in time. The dataset presented in this study may be of sufficient quality to allow historians to better assess the environmental and social impacts of the harsh weather. [ABSTRACT FROM AUTHOR]

Climate anomalies over North America and Europe are closely related to the North Atlantic Oscillation (NAO). The persistence, decay or switch of the NAO phase across the boreal winter determines whether the NAO‐related climate anomalies are sustained, weakened or reversed during the boreal winter. This study compares the spatiotemporal evolution of atmospheric wind and sea surface temperature (SST) anomalies over the North Atlantic corresponding to persistence and switch of the NAO phase across the boreal winter. It is revealed that the persistence of the NAO from early to late winter is associated with a strong coupling between the NAO and the North Atlantic tripole SST anomalies. The formation of the tripole SST anomalies is attributed to the wind‐related surface latent heat flux changes. The tripole SST anomalies feedback on the NAO through eddy‐mean flow interaction. In contrast, during the winters with the switch of the NAO phase, the North Atlantic SST anomalies follow the wind changes, but do not have obvious feedback on the NAO. Our analysis identifies a prominent change of the winter NAO evolution in the early 1990s. The NAO switches its phase from early to late winter during 1970s through the early 1990s, but tends to maintain its phase during the boreal winter after the early 1990s. This interdecadal change appears to be related to the mean SST change. The SST increase in both the tropical and mid‐latitude North Atlantic Ocean in the early 1990s enhances the feedback of the NAO‐induced tripole SST anomalies on the NAO. Plain Language Summary: The North Atlantic Oscillation (NAO) is an important climate mode in the North Atlantic region. It has a large influence on climate in the surrounding regions. Different phases of the NAO are accompanied by distinct climate anomalies over North America and Europe. The persistence, decay or phase transition of the NAO across the boreal winter signifies the sustenance, weakening or reversal of the associated climate anomalies. This study reveals that the temporal evolution of the NAO from early to late winter is associated with the role of the North Atlantic air‐sea coupling. When the NAO is coupled closely with the North Atlantic tripole sea surface temperature anomalies, the air‐sea coupling processes maintain the phase of the NAO. When the air‐sea coupling is weak over the North Atlantic Ocean, the internal atmospheric processes control the temporal evolution of wind anomalies over the North Atlantic Ocean. In that case, the NAO cannot maintain its phase through the boreal winter and it either decays or switches its phase from early to late winter. The NAO tends to switch and maintain its phase during the boreal winter during 1970s‐early 1990s and after the early 1990s, respectively. Key Points: The North Atlantic Oscillation (NAO) displays two distinct evolutions across the boreal winter with the same phase persisting and a switch of the phaseThe NAO phase persistence is associated with a strong coupling between the NAO and the North Atlantic tripole sea surface temperature anomaliesThe winter NAO evolution experienced an interdecadal change from the phase switch to the phase persisting dominant in the early 1990s [ABSTRACT FROM AUTHOR]

Black kites of the nominal subspecies Milvus migrans migrans breed in Europe and winter regularly in sub-Saharan Africa and the Middle East. As a new phenomenon, black kites with morphological characteristics of the subspecies Milvus migrans lineatus are observed in Europe. Based on observations of black kites in winter 2020/2021 summarized in this paper, based on other recent reports about wintering black kites in Europe and based on juvenile black kite tagged on Crete and tracked for two years, we conclude that hundreds to thousands of black kites are now regularly wintering in south of Europe, and in smaller numbers in other parts of Europe as well as in northern Africa. The growing number of wintering black kites in Europe is apparently caused by members of the population from a hybrid zone between M. m. migrans and M. m. lineatus breeding east of the Urals, i.e. from the area of the European part of Russia. This is consistent with the hypothesis of the spreading of M. m. lineatus and a subsequent hybridization zone between M. m. migrans and M. m. lineatus in a westerly direction from Siberia across continental Europe. Moreover, two black kites found dead on Crete were attributed to M. m. lineatus and M. m. migrans by cytochrome B gene sequence analyses. The juvenile black kite with lineatus features tagged on Crete and telemetrically tracked during the next two years moved to the south-western part of Russia during the next two summers, but did not breed. It spent the following two winters at the same landfill in south-western Turkey. It seems that an adaptation to food sources provided by municipal waste landfills is important for black kites wintering in Europe, the Middle East and Morocco. Highlights • Hundreds to thousands of black kites are now regularly wintering in Europe. • The growing number of wintering black kites is caused by birds from a hybrid zone between Milvus migrans migrans and M. m. lineatus in eastern Europe. • Municipal waste landfills are important as food sources for black kites wintering in Europe. [ABSTRACT FROM AUTHOR]

Variability of the North Atlantic Oscillation (NAO) drives wintertime temperature anomalies in the Northern Hemisphere. Dynamical seasonal prediction systems can skilfully predict the winter NAO. However, prediction of the NAO‐dependent air temperature anomalies remains elusive, partially due to the low variability of predicted NAO. Here, we demonstrate a hidden potential of a multi‐model ensemble of operational seasonal prediction systems for predicting wintertime temperature by increasing the variability of predicted NAO. We identify and subsample those ensemble members which are close to NAO index statistically estimated from initial autumn conditions. In our novel multi‐model approach, the correlation prediction skill for wintertime Central Europe temperature is improved from 0.25 to 0.66, accompanied by an increased winter NAO prediction skill of 0.9. Thereby, temperature anomalies can be skilfully predicted for the upcoming winter over a large part of the Northern Hemisphere through increased variability and skill of predicted NAO. Plain Language Summary: Wintertime temperature in the Northern Hemisphere is regulated by the variations of atmospheric pressure, represented by the so‐called North Atlantic Oscillation (NAO). The NAO's phase—negative or positive—is associated with the pathways of cold and warm air masses leading to cold or warm winters in Europe. While the NAO phase can be predicted well, predictions of the NAO‐dependent air temperature remain elusive. Specifically, it is challenging to predict the strength of the NAO, the most important requirement for the accurate prediction of wintertime temperature. Here, we improve wintertime temperature prediction by increasing the strength of the predicted NAO. We use observation based autumn Northern Hemisphere ocean and air temperature, as well as ice and snow cover for statistical estimation of the first guess NAO for the upcoming winter. Then, we sub‐select only those simulations from the multi‐model ensemble, which are consistent with our first guess NAO. As a result, based on these selected members, the wintertime temperature prediction is substantially improved over a large part of the Northern Hemisphere. Key Points: Amplitude and skill of predicted North Atlantic Oscillation (NAO) improve significantly by subsampling of ensemble of existing seasonal prediction systemsAmplified NAO variability leads to significant improvement in predicting the upcoming winter temperature anomalies in the Northern Hemisphere [ABSTRACT FROM AUTHOR]

Climate models generally project an increase in the winter North Atlantic Oscillation (NAO) index under a future high‐emissions scenario, alongside an increase in winter precipitation in northern Europe and a decrease in southern Europe. The extent to which future forced NAO trends are important for European winter precipitation trends and their uncertainty remains unclear. We show using the Multimodel Large Ensemble Archive that the NAO plays a small role in northern European mean winter precipitation projections for 2080–2099. Conversely, half of the model uncertainty in southern European mean winter precipitation projections is potentially reducible through improved understanding of the NAO projections. Extreme positive NAO winters increase in frequency in most models as a consequence of mean NAO changes. These extremes also have more severe future precipitation impacts, largely because of mean precipitation changes. This has implications for future resilience to extreme positive NAO winters, which frequently have severe societal impacts. Plain Language Summary: Variations in atmospheric circulation over the North Atlantic are dominated by the North Atlantic Oscillation (NAO) pattern. A positive NAO phase is associated with a northward shift of the North Atlantic storm track, bringing wetter weather to northern Europe and drier weather to southern Europe. In future scenarios with increases in human‐caused greenhouse gas emissions, climate models generally simulate an increase in the winter NAO, alongside an increase in winter precipitation in northern Europe and a decrease in southern Europe. However, it is unclear what role the NAO plays in future European winter precipitation trends. Here we show, using a large number of simulations from different climate models, that the NAO plays a small role in late 21st century northern European winter precipitation changes. Conversely, the NAO plays a sizable role in southern Europe. This is important because it suggests that uncertainty in southern European winter precipitation changes could be partly reduced with improved understanding of future NAO changes. Winters with an extremely positive NAO state are generally projected to increase in frequency and have larger precipitation impacts. This has implications for future resilience to these seasonal extremes, which already can have severe societal impacts including flooding and drought. Key Points: The North Atlantic Oscillation (NAO) explains half of model spread in southern European winter precipitation change by 2080–2099 for RCP8.5Extreme positive NAO winters may increase in frequency in future by up to 35%, due to mean NAO change, but there is large model uncertaintyExtreme positive NAO winters have more severe future precipitation impacts, with implications for resilience to this type of extreme season [ABSTRACT FROM AUTHOR]

Winter temperature‐related chilling and spring temperature‐related forcing are two major environmental cues shaping the leaf‐out date of temperate species. To what degree insufficient chilling caused by winter warming would slow phenological responses to spring warming remains unclear. Using 27,071 time series of leaf‐out dates for 16 tree species in Europe, we constructed a phenological model based on the linear or exponential function between the chilling accumulation (CA) and forcing requirements (FR) of leaf‐out. We further used the phenological model to quantify the relative contributions of chilling and forcing on past and future spring phenological change. The results showed that the delaying effect of decreased chilling on the leaf‐out date was prevalent in natural conditions, as more than 99% of time series exhibited a negative relationship between CA and FR. The reduction in chilling linked to winter warming from 1951 to 2014 could offset about one half of the spring phenological advance caused by the increase in forcing. In future warming scenarios, if the same model is used and a linear, stable correlation between CA and FR is assumed, declining chilling will continuously offset the advance of leaf‐out to a similar degree. Our study stresses the importance of assessing the antagonistic effects of winter and spring warming on leaf‐out phenology. [ABSTRACT FROM AUTHOR]

Eurasian Woodcock (Scolopax rusticola) plays a special role in the cultural heritage of most nations in Europe. In the last decade, ringing revealed the main migratory patterns of some well studied and intensively harvested Woodcock populations wintering in Western and Southern Europe. The same study sites and populations were in focus when the recently revolutionized satellite tracking technologies allowed the study of individual migrations. In contribution to these efforts, we present here the pre-nuptial migration data of Woodcocks captured and tagged with GPS-Argos transmitters in Central Europe, in 2020. Woodcocks migrated from the tagging site in Hungary to Ukraine, European Russia and Central Siberia by an average of 2,678 km (range 677-5,002 km). The duration of the migration ranged between 1-52 days, the overall migration speed was 382 km/day, the absolute maximum distance covered in a day was 866 km. The individual number of stopovers varied during the migration from 0 to 5. The average time spent at each stopover site was 5.6 days. Within the stopover sites, the daily displacements ranged between 11-3,329 m. The Carpathian Basin may be more important in the wintering of Woodcocks than previously assumed, as tagged birds stayed significantly longer compared to any later en route migratory stopover. In accordance with the results of previous DNA analysis, identified breeding grounds of tagged individuals represented a large part of the distribution area. [ABSTRACT FROM AUTHOR]

Rye is the only cross-pollinating small-grain cereal. The unique reproduction biology results in an exceptional complexity concerning genetic improvement of rye by breeding. Rye is a close relative of wheat and has a strong adaptation potential that refers to its mating system, making this overlooked cereal readily adjustable to a changing environment. Rye breeding addresses the emerging challenges of food security associated with climate change. The systematic identification, management, and use of its valuable natural diversity became a feasible option in outbreeding rye only following the establishment of hybrid breeding late in the 20th century. In this article, we review the most recent technological advances to improve yield and yield stability in winter rye. Based on recently released reference genome sequences, SMART breeding approaches are described to counterbalance undesired linkage drag effects of major restorer genes on grain yield. We present the development of gibberellin-sensitive semidwarf hybrids as a novel plant breeding innovation based on an approach that is different from current methods of increasing productivity in rye and wheat. Breeding of new rye cultivars with improved performance and resilience is indispensable for a renaissance of this healthy minor cereal as a homogeneous commodity with cultural relevance in Europe that allows for comparatively smooth but substantial complementation of wheat with rye-based diets, supporting the necessary restoration of the balance between human action and nature. [ABSTRACT FROM AUTHOR]

Although seasonal variation has a known influence on the transmission of several respiratory viral infections, its role in SARS-CoV-2 transmission remains unclear. While there is a sizable and growing literature on environmental drivers of COVID-19 transmission, recent reviews have highlighted conflicting and inconclusive findings. This indeterminacy partly owes to the fact that seasonal variation relates to viral transmission by a complicated web of causal pathways, including many interacting biological and behavioural factors. Since analyses of specific factors cannot determine the aggregate strength of seasonal forcing, we sidestep the challenge of disentangling various possible causal paths in favor of a holistic approach. We model seasonality as a sinusoidal variation in transmission and infer a single Bayesian estimate of the overall seasonal effect. By extending two state-of-the-art models of non-pharmaceutical intervention (NPI) effects and their datasets covering 143 regions in temperate Europe, we are able to adjust our estimates for the role of both NPIs and mobility patterns in reducing transmission. We find strong seasonal patterns, consistent with a reduction in the time-varying reproduction number R(t) (the expected number of new infections generated by an infectious individual at time t) of 42.1% (95% CI: 24.7%—53.4%) from the peak of winter to the peak of summer. These results imply that the seasonality of SARS-CoV-2 transmission is comparable in magnitude to the most effective individual NPIs but less than the combined effect of multiple interventions. Author Summary: Building on two state-of-the-art observational models and datasets, we adapt a fully Bayesian method for estimating the association between seasonality and SARS-CoV-2 transmission in 143 temperate European regions. This approach overcomes limitations of previous analyses that do not account for the implementation of non-pharmaceutical interventions (NPIs) or mobility during the first year of the pandemic and hence may yield biased estimates of seasonal effects. We find that the seasonality of SARS-CoV-2 transmission is comparable in magnitude to the most effective individual NPIs but less than the combined effect of multiple interventions. Our findings provide valuable insights for long-term modelling and policy planning. As seasons change, it is vital that policymakers employ accurate estimates of seasonal effects. In the summer, reductions in transmission that owe to seasonality should not be misattributed to population immunity. In the winter, policymakers must avoid anticipating a greater reduction due to seasonality than will actually occur. [ABSTRACT FROM AUTHOR]

The ecology and evolution of reproductive timing and synchrony have been a topic of great interest in evolutionary ecology for decades. Originally motivated by questions related to behavioral and reproductive adaptation to environmental conditions, the topic has acquired new relevance in the face of climate change. However, there has been relatively little research on reproductive phenology in mammalian carnivores. The Eurasian lynx (Lynx lynx) occurs across the Eurasian continent, covering three of the four main climate regions of the world. Thus, their distribution includes a large variation in climatic conditions, making it an ideal species to explore reproductive phenology. Here, we used data on multiple reproductive events from 169 lynx females across Europe. Mean birth date was May 28 (April 23 to July 1), but was ~10 days later in northern Europe than in central and southern Europe. Birth dates were relatively synchronized across Europe, but more so in the north than in the south. Timing of birth was delayed by colder May temperatures. Severe and cold weather may affect neonatal survival via hypothermia and avoiding inclement weather early in the season may select against early births, especially at northern latitudes. Overall, only about half of the kittens born survived until onset of winter but whether kittens were born relatively late or early did not affect kitten survival. Lynx are strict seasonal breeders but still show a degree of flexibility to adapt the timing of birth to surrounding environmental conditions. We argue that lynx give birth later when exposed to colder spring temperatures and have more synchronized births when the window of favorable conditions for raising kittens is shorter. This suggests that lynx are well adapted to different environmental conditions, from dry and warm climates to alpine, boreal, and arctic climates. This variation in reproductive timing will be favorable in times of climate change, as organisms with high plasticity are more likely to adjust to new environmental conditions. [ABSTRACT FROM AUTHOR]

Wind has a significant yet complex effect on bird migration speed. With prevailing south wind, overall migration is generally faster in spring than in autumn. However, studies on the difference in airspeed between seasons have shown contrasting results so far, in part due to their limited geographical or temporal coverage. Using the first full‐year weather radar data set of nocturnal bird migration across western Europe together with wind speed from reanalysis data, we investigate variation of airspeed across season. We additionally expand our analysis of ground speed, airspeed, wind speed, and wind profit variation across time (seasonal and daily) and space (geographical and altitudinal). Our result confirms that wind plays a major role in explaining both temporal and spatial variabilities in ground speed. The resulting airspeed remains relatively constant at all scales (daily, seasonal, geographically and altitudinally). We found that spring airspeed is overall 5% faster in Spring than autumn, but we argue that this number is not significant compared to the biases and limitation of weather radar data. The results of the analysis can be used to further investigate birds' migratory strategies across space and time, as well as their energy use. [ABSTRACT FROM AUTHOR]

Although several studies have concluded that excess winter deaths are not a suitable indicator of cold-related health impacts, the investigation of temporal fluctuation in mortality across many European countries could provide an insight into the seasonal variation of deaths at different climatic conditions. We investigated the evolution over time of the Excess Winter Deaths Index (EWDI) and the Summer-to-Winter Deaths ratio (S/W) for the period 1960–2018 and the temporal fluctuation of the Heating and Cooling Degree Days indices for the period 1979–2020. We found a clear spatial pattern of EWDI with statistically significant decreasing trends in Mediterranean countries and increasing trends in Nordic countries. On the other hand, S/W index shown increasing trends in Mediterranean region and decreasing trends in Nordic countries. Statistical analysis of Heating Degree Days index showed significant decreasing trends for all European countries, probably due to the appearance of milder winters. Also, the values of Cooling Degree Days index exhibited a statistically significant upward trend for Mediterranean countries, mainly due to increased frequency of warmer summers, as a result of climate change. This study shows that the differences in seasonal variation of mortality between European countries are likely to disappear, as the climate gets warmer. A possible explanation for our findings is that climate change already brings milder winters and hotter summers to the Mediterranean countries, while in the Nordic countries global warming causes less severe winters and more pleasant summers as shown from Heating and Cooling Degree Days analysis. In addition to providing a basis to investigate potential effects of global warming on human mortality, the findings of this study are likely to be crucial for climate change policy and developing relevant adaptation strategies in Europe. [ABSTRACT FROM AUTHOR]

During the years 2019 and 2020, I conducted a bird survey transect in the Bohemian Forest. I did not record any changes in habitat structure or weather conditions between the two years. The two surveys differed in sampling effort, which was significantly lower in 2020 (n = 5 visits) than 2019 (n = 14 visits). I found that sampling effort affected the assessment of avian community diversity but did not affect the total number of individuals recorded. I also recorded a similar pattern in the cumulative number of species between the two breeding seasons, but 80% of species were recorded ten days earlier with the higher sampling effort. In the year with the lower sampling effort, I recorded fewer species than in the year with higher sampling effort. In both study periods, avian community diversity peaked during May and June. These results suggest that even a sampling effort three times lower is still sufficient to detect most species if the minimal number of visits are conducted. The pattern of detectability during the breeding season differed significantly among species. Most species (n = 24) showed a decreasing linear detectability throughout the summer months (e.g. Turdidae or Muscicapidae), most probably due to their breeding activities. In two species (willow tit Poecile montanus and European goldfinch Carduelis carduelis), this linear relationship was reversed, probably due to singing of young birds from the previous breeding season and the effect of the autumn equinox on birdsong activity. Many species (n = 21) did not show any trend and the rest, mainly migratory species, showed non-linear relationships with the peak in the middle of the breeding season. The differences in trends of detectability (i.e. song activity) among bird species are therefore directly linked with their life history. [ABSTRACT FROM AUTHOR]

We studied spatial and temporal patterns of precipitation–temperature (P–T) relationships through correlations between monthly standardized precipitation index (SPI) and monthly temperature anomalies in individual climatic seasons over Europe. In the observed data (represented by E‐OBS), positive correlations (wet–warm/dry–cold relationships) prevail during winter over most of Europe, while negative values (dry–warm/wet–cold) are dominant in summer. In the next step, an ensemble of seven regional climate models (RCMs) from the CORDEX project driven by the ERA‐Interim reanalysis were examined as to their reproduction of the regional patterns of the P–T correlations. In winter, the RCMs yielded overly strong positive P–T correlations over northern Europe, while the correlations were too weak in the south compared to observed data. During summer, the biases were generally larger; the RCMs were able to capture the overall negative P–T correlations but these tended to be too weak over northern Europe. This deficiency was found to be linked to simulated differences in shortwave radiation (a proxy for cloud cover) between dry and wet months. In western, central, and southeastern Europe, by contrast, most RCMs yielded too strong negative correlations in summer, and overly large decreases of relative humidity during dry months probably contributed to these errors. The results pointed up issues that should be addressed as the reported RCMs' deficiencies may lower credibility of projected compound dry–hot events in climate change scenarios. [ABSTRACT FROM AUTHOR]

Background and Aims European ancient woodlands are subject to land use change, and the distribution of herbaceous understorey species may be threatened because of their poor ability to colonize isolated forest patches. The regeneration niche can determine the species assembly of a community, and seed germination traits may be important descriptors of this niche. Methods We analysed ecological records for 208 herbaceous species regarded as indicators of ancient woodlands in Europe and, where possible, collated data on seed germination traits, reviewed plant regeneration strategies and measured seed internal morphology traits. The relationship between plant regeneration strategies and ecological requirements was explored for 57 species using ordination and classification analysis. Key Results Three regeneration strategies were identified. Species growing in closed-canopy areas tend to have morphological seed dormancy, often requiring darkness and low temperatures for germination, and their shoots emerge in early spring, thus avoiding the competition for light from canopy species. These species are separated into two groups: autumn and late winter germinators. The third strategy is defined by open-forest plants with a preference for gaps, forest edges and riparian forests. They tend to have physiological seed dormancy and germinate in light and at higher temperatures, so their seedlings emerge in spring or summer. Conclusion Seed germination traits are fundamental to which species are good or poor colonizers of the temperate forest understorey and could provide a finer explanation than adult plant traits of species distribution patterns. Seed dormancy type, temperature stratification and light requirements for seed germination are important drivers of forest floor colonization patterns and should be taken in account when planning successful ecological recovery of temperate woodland understories. [ABSTRACT FROM AUTHOR]

European winter weather is dominated by several low‐frequency teleconnection patterns, the main ones being the North Atlantic Oscillation, East Atlantic, East Atlantic/Western Russia, and Scandinavian patterns. We analyze the century‐long ERA‐20C reanalysis and ASF‐20C seasonal hindcast data sets and find that these patterns are subject to decadal variability and fluctuations in predictive skill. Using indices for determining periods of extreme cold or warm temperatures, we establish that the teleconnection patterns are, for some regions, significantly correlated or anti‐correlated to cold or heat waves. The seasonal hindcasts are however only partly able to capture these relationships. There do not seem to be significant changes to the observed links between large‐scale circulation patterns and extreme temperatures between periods of higher and lower predictive skill. Plain Language Summary: Large‐scale atmospheric patterns that influence European winter weather showed slowly evolving fluctuations over the course of the twentieth century. This affects how well the patterns can be predicted by seasonal forecasting models. However, the impact of the large‐scale patterns on extreme winter temperatures mostly does not change over time, although forecasting models often struggle to correctly predict these impacts. Key Points: The predictive skill of winter seasonal hindcasts for teleconnection patterns in Europe varied over the twentieth centurySeasonal hindcasts only partly reproduce the links between teleconnection patterns and winter temperature extremesThe teleconnection/surface temperature relationships do not significantly change despite fluctuations in predictive skill [ABSTRACT FROM AUTHOR]

The strong multidecadal variability in North Atlantic (NA) winter atmospheric circulation is poorly understood and appears too weak in climate models. Recent research has shown peak atmospheric multidecadal variability over the NA in late winter, particularly March, linked to Atlantic multidecadal variability (AMV) of the ocean. Here a range of NA atmospheric circulation indices are assessed to provide a comprehensive picture of early‐to‐late winter low‐frequency variability and its representation in the latest generation of climate models (Coupled Model Intercomparison Project Phase 6 [CMIP6]). As found for CMIP5, CMIP6 models exhibit too‐weak multidecadal NA atmospheric variability compared to reanalysis data over the period 1862–2005. Consistent with previous research, the eastern part of the NA westerly jet (U700NA) exhibits peak low‐frequency variability in March. However, for NA‐wide jet speed and the NAO, low‐frequency variability and model‐reanalysis discrepancies are strongest in January and February, associated with too‐weak NA ocean‐atmosphere linkages. Plain Language Summary: The strong low‐frequency multidecadal variability of large‐scale atmospheric circulation in the North Atlantic (NA) drives variability in climate conditions over western Europe. Reliably reproducing this variability in climate models is of high importance for estimating future climatic conditions. However, a current issue in climate modeling is that models generally exhibit weak winter multidecadal variability compared to estimates based on observationally constrained reconstructions (reanalyses). In particular recent research has shown that strong low‐frequency atmospheric variability and associated discrepancies between models and reanalyses are most pronounced in late winter, particularly March. The first step in this study is to establish that the current generation of climate models still exhibit the long‐standing issue that simulated multidecadal variability of NA atmospheric circulation is weaker than in reanalyses. A subseasonal analysis shows that, consistent with previous research, the eastern part of the NA westerly jet exhibits peak low‐frequency variability in March. However, for NA‐wide indices, tropospheric westerly jet speed and the NAO, low‐frequency variability is strongest in January and February. Evidence is shown suggesting that these inter‐index differences in subseasonal variability are associated with differences in monthly correlations with NA subpolar gyre SSTs. Key Points: Climate models exhibit systematically weak winter multidecadal North Atlantic (NA) atmospheric variability relative to reanalysis outputThe subseasonal timing of 20th century winter variability is sensitive to the choice of atmospheric circulation indexOnset of strong variability occurs earliest for NA jet speed (December), followed by NAO (January) and eastern‐NA jet speed (February) [ABSTRACT FROM AUTHOR]

The impacts of Arctic stratospheric polar vortex (SPV) on wintertime precipitation over the Northern Hemisphere are analyzed based on various datasets. Two groups of ensemble climate model experiments with the SPV nudged towards strong and weak states are performed to clarify stratospheric impacts on changes in precipitation. During weak SPV events, precipitation rates over the western and southeastern parts of North Pacific Ocean, the southern part of North Atlantic Ocean, and Southern Europe are larger, whereas the total precipitation rates over the central North Pacific, the northern part of North Atlantic and Northern Europe are smaller than those during strong SPV events. The SPV-induced changes in precipitation over the North Atlantic are stronger than those over the North Pacific. The convective (large-scale) precipitation changes play a major role in the total precipitation changes over the southern (northern) parts of middle latitudes associated with SPV changes. The tropospheric zonal wind deceleration around 60°N associated with weak SPV events is responsible for lower-tropospheric anomalous cyclonic flows over the two oceans at middle latitudes. The anomalous cyclonic flows lead to more large-scale precipitation in the southeastern parts of the oceans and less large-scale precipitation over Northern Europe and the central North Pacific during weak SPV events. The stratosphere–troposphere coupling over the North Atlantic is stronger than that over the North Pacific, leading to stronger large-scale precipitation responses over the former region. In addition, convective precipitation rates between 30 and 45°N are basically larger during weak SPV events than during strong SPV events. This is because more baroclinic waves associated with a southward shift of storm tracks during weak SPV events cause more heat exchanges between the lower latitudes and higher latitudes. Consequently, the upper tropospheric temperature and static ability between 30 and 45°N are reduced, leading to larger convective available potential energy and more convective precipitation during weak SPV events. [ABSTRACT FROM AUTHOR]