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The projected winter changes of the North Atlantic eddy-driven jet (EDJ) under climate change conditions have been extensively analysed. Previous studies have reported a squeezed and elongated EDJ. However, other changes present large uncertainties, specifically those related to the intensity and latitude. Here, the projections of the EDJ in a multimodel ensemble of CMIP6 are scrutinised by using a multiparametric description of the EDJ. The multimodel mean projects non-stationary responses of the EDJ latitude through the winter, characterised by a poleward shift in early winter and equator migration in late winter. These intraseasonal shifts (rather than a genuine narrowing) explain the previously established squeezing of the EDJ and are linked to the future changes in different drivers: the 200 hPa meridional temperature gradient and Atlantic warming hole in early winter, and the stratospheric vortex in late winter. Model biases also influence EDJ projections, contributing to the poleward shift in early winter. [ABSTRACT FROM AUTHOR]

This study analyzes the relationship between drought processes and crop yields in Moldova, together with the effects of possible future climate change on crops. The severity of drought is analyzed over time in Moldova using the Standard Precipitation Index, the Standardized Precipitation Evapotranspiration Index, and their relationship with crop yields. In addition, rainfall variability and its relationship with crop yields are examined using spectral analysis and squared wavelet coherence. Observed station data (1950–2020 and 1850–2020), ERA5 reanalysis data (1950–2020), and climate model simulations (period 1970–2100) are used. Crop yield data (maize, sunflower, grape), data from experimental plots (wheat), and the Enhanced Vegetation Index from Moderate Resolution Imaging Spectroradiometer satellites were also used. Results show that although the severity of meteorological droughts has decreased in the last 170 years, the impact of precipitation deficits on different crop yields has increased, concurrent with a sharp increase in temperature, which negatively affected crop yields. Annual crops are now more vulnerable to natural rainfall variability and, in years characterized by rainfall deficits, the possibility of reductions in crop yield increases due to sharp increases in temperature. Projections reveal a pessimistic outlook in the absence of adaptation, highlighting the urgency of developing new agricultural management strategies. [ABSTRACT FROM AUTHOR]

The article titled "The first intrusion of Saharan dust in the Canary Islands, scientifically documented and known (February 7, 1863)" talks about the first time the presence of Saharan dust in the Canary Islands was scientifically documented. Charles Darwin conducted an analysis aboard the brig "Beagle" in 1863, collecting dust particle samples and analyzing their size. Sabin Berthelot scientifically described a dust intrusion in the Canary Islands on February 7, 1863. The article highlights the importance of being cautious when linking these patterns to climate change due to the short observational record and limited understanding of associated synoptic patterns. [Extracted from the article]

Atmospheric extreme events cause severe damage to human societies and ecosystems. The frequency and intensity of extremes and other associated events are continuously increasing due to climate change and global warming. The accurate prediction, characterization, and attribution of atmospheric extreme events is, therefore, a key research field in which many groups are currently working by applying different methodologies and computational tools. Machine learning and deep learning methods have arisen in the last years as powerful techniques to tackle many of the problems related to atmospheric extreme events. This paper reviews machine learning and deep learning approaches applied to the analysis, characterization, prediction, and attribution of the most important atmospheric extremes. A summary of the most used machine learning and deep learning techniques in this area, and a comprehensive critical review of literature related to ML in EEs, are provided. The critical literature review has been extended to extreme events related to rainfall and floods, heatwaves and extreme temperatures, droughts, severe weather events and fog, and low-visibility episodes. A case study focused on the analysis of extreme atmospheric temperature prediction with ML and DL techniques is also presented in the paper. Conclusions, perspectives, and outlooks on the field are finally drawn. [ABSTRACT FROM AUTHOR]

Air pollution is a major environmental threat to human health. Pollutants can reach extreme levels in the lower atmosphere when weather conditions permit. As pollutant concentrations depend on scales and processes that are not fully represented in current global circulation models (GCMs), and it is often too computationally expensive to run models with atmospheric chemistry and aerosol processes, air stagnation is often used as a proxy for pollution events with particular success in Europe. However, the variables required to identify air stagnation can have biases in GCM output, which adds uncertainty to projected trends in air stagnation. Here, the representation of air stagnation in GCMs is assessed for Europe in the historical period and in end-of-century projections based on a high-emission scenario using three methods for identifying air stagnation. The monthly frequency of stagnation during summer and autumn is projected to increase with climate change when stagnation is identified by a well-established index. However, this increase is not present when air-stagnation frequency is estimated using a statistical model based on the synoptic- to large-scale atmospheric circulation. This implies that the projected increases in air stagnation are not driven by an increase in frequency or severity of large-scale circulation events that are conducive to stagnation. Indeed, projected changes to the atmospheric circulation in GCMs, in particular a reduction in atmospheric block frequency, would suggest a reduction in future air stagnation. Additional analyses indicate that the projected increases in stagnation frequency follow the trend toward more frequent dry days, which is apparently unrelated to the large-scale drivers of air stagnation. [ABSTRACT FROM AUTHOR]

Main modes of atmospheric variability exert a significant influence on weather and climate at local and regional scales on all time scales. However, their past changes and variability over the instrumental record are not well constrained due to limited availability of observations, particularly over the oceans. Here we couple a reconstruction method with an evolutionary algorithm to yield a new 1° × 1° optimized reconstruction of monthly North Atlantic sea level pressure since 1750 from a network of meteorological land and ocean observations. Our biologically inspired optimization technique finds an optimal set of weights for the observing network that maximizes the reconstruction skill of sea level pressure fields over the North Atlantic Ocean, bringing significant improvements over poorly sampled oceanic regions, as compared to non-optimized reconstructions. It also reproduces realistic variations of regional climate patterns such as the winter North Atlantic Oscillation and the associated variability of the subtropical North Atlantic high and the subpolar low pressure system, including the unprecedented strengthening of the Azores high in the second half of the twentieth century. We find that differences in the winter North Atlantic Oscillation indices are partially explained by disparities in estimates of its Azores high center. Moreover, our reconstruction also shows that displacements of the summer Azores high center toward the northeast coincided with extremely warm events in western Europe including the anomalous summer of 1783. Overall, our results highlight the importance of improving the characterization of the Azores high for understanding the climate of the Euro-Atlantic sector and the added value of artificial intelligence in this avenue. [ABSTRACT FROM AUTHOR]

This study explores the uncertainty of future summer warming over Iberia using storylines constructed from climate model simulations of the Climate Model Intercomparison Project Phase 6. Unlike prior storyline approaches focusing on remote drivers and global teleconnections of atmospheric circulation, we use regional factors that directly influence summer temperatures: ridging activity, soil moisture and Mediterranean sea surface temperature. These drivers explain a substantial portion of the observed variability across climate models, with ridging activity and soil moisture showing the strongest influence on Iberian warming. Under a high radiative forcing scenario (SSP5–8.5), the storylines of Iberian warming based on these two drivers range between 7 and 9 °C for the end of the 21st century. The storyline leading to the largest warming is characterised by a drying out of the soil conditions and an increase in the anticyclonic activity over Iberia. We find similar conclusions for simple extreme heat indicators, though the approach struggles with more complex heatwave metrics. We also propose a novel modification of the storyline approach to increase the data sample of climate responses by using different time intervals throughout the 21st century. This modification would allow the application of more complex statistical models, the exploration of non-linear relationships and the identification of other drivers shaping the regional climate projections. • Soil moisture & ridging explain most multi-model spread of Iberian warming (IW). • Storylines of IW range between ∼1.6–2.1 °C per degree of global warming. • The influence of Mediterranean sea surface temperatures on IW is of secondary importance. • Similar findings on extreme temperatures, but complex metrics pose challenges. • Novel modification of the storyline approach: extending data via moving windows. [ABSTRACT FROM AUTHOR]

The present study analyses changes in the timing and duration of the hot days season over the Middle East and North Africa region from 1970 to 2099 using model simulations of 11 regional models from the Coordinated Regional Climate Downscaling Experiment under the RCP8.5 scenario. In general, a non‐symmetrical lengthening of the hot days season is projected, with a tendency to extend more into spring than into autumn. By the end of the century and the RCP8.5 scenario, Western Africa and the Persian Gulf display a hot days season starting 60 days earlier than in the historical period (1970–1999) (May vs. July, respectively). Southernmost latitudes are the most affected by a later retreat of the hot days season, of up to 60 days with respect to the historical period (October vs. August). The length of the extreme season is projected to increase between 100 and 120 days for the southernmost latitudes and the Persian Gulf resulting in nearly four more months with hot days conditions. [ABSTRACT FROM AUTHOR]

Over the last decade, the world warmed by 0.25 °C, in-line with the roughly linear trend since the 1970s. Here we present updated analyses showing that this seemingly small shift has led to the emergence of heat extremes that would be virtually impossible without anthropogenic global warming. Also, record rainfall extremes have continued to increase worldwide and, on average, 1 in 4 rainfall records in the last decade can be attributed to climate change. Tropical regions, comprised of vulnerable countries that typically contributed least to anthropogenic climate change, continue to see the strongest increase in extremes. [ABSTRACT FROM AUTHOR]

We have analyzed the record-breaking drought that affected western and central Europe from July 2016 to June 2017. It caused widespread impacts on water supplies, agriculture, and hydroelectric power production, and was associated with forest fires in Iberia. Unlike common continental-scale droughts, this event displayed a highly unusual spatial pattern affecting both northern and southern European regions. Drought conditions were observed over 90% of central-western Europe, hitting record-breaking values (with respect to 1979–2017) in 25% of the area. Therefore, the event can be considered as the most severe European drought at the continental scale since at least 1979. The main dynamical forcing of the drought was the consecutive occurrence of blocking and subtropical ridges, sometimes displaced from their typical locations. This led to latitudinal shifts of the jet stream and record-breaking positive geopotential height anomalies over most of the continent. The reduction in moisture transport from the Atlantic was relevant in the northern part of the region, where decreased precipitation and increased sunshine duration were the main contributors to the drought. On the other hand, thermodynamic processes, mostly associated with high temperatures and the resulting increase in atmospheric evaporative demand, were more important in the south. Finally, using flow circulation analogs we show that this drought was more severe than it would have been in the early past. [ABSTRACT FROM AUTHOR]

Blocking occurrence and its impacts on European temperature have been studied in the last decade. However, most previous studies on blocking impacts have focused on winter only, disregarding its fingerprint in summer and differences with other synoptic patterns that also trigger temperature extremes. In this work, we provide a clear distinction between high-latitude blocking and sub-tropical ridges occurring in three sectors of the Euro-Atlantic region, describing their climatology and consequent impacts on European temperature during both winter and summer. Winter blocks (ridges) are generally associated to colder (warmer) than average conditions over large regions of Europe, in some areas with anomalies larger than 5 °C, particularly for the patterns occurring in the Atlantic and Central European sectors. During summer, there is a more regional response characterized by above average temperature for both blocking and ridge patterns, especially those occurring in continental areas, although negative temperature anomalies persist in southernmost areas during blocking. An objective analysis of the different forcing mechanisms associated to each considered weather regime has been performed, quantifying the importance of the following processes in causing the temperature anomalies: horizontal advection, vertical advection and diabatic heating. While during winter advection processes tend to be more relevant to explain temperature responses, in summer radiative heating under enhanced insolation plays a crucial role for both blocking and ridges. Finally, the changes in the distributions of seasonal temperature and in the frequencies of extreme temperature indices were also examined for specific areas of Europe. Winter blocking and ridge patterns are key drivers in the occurrence of regional cold and warm extreme temperatures, respectively. In summer, they are associated with substantial changes in the frequency of extremely warm days, but with different signatures in southern Europe. We conclude that there has been some misusage of the traditional blocking definition in the attribution of extreme events. [ABSTRACT FROM AUTHOR]

This talk provides an overview of several extreme events that affected Europe in the last years (2016-2018). The assessment focuses on the exceptionality of these events, considering the ongoing climate change and the associated synoptic circulation by using multiple approaches to diagnose extreme events and weather systems.July 2016 to June 2017 recorded the most severe European drought at continental scale since at least 1979, causing widespread impacts in water supply, agriculture and hydroelectric production. The event featured a highly unusual spatial pattern affecting northern and southern Europe, due to an alternating occurrence of high-latitude blocks and subtropical ridges that triggered precipitation deficits in the north and warming in the south, respectively. The drought peak in June 2017 coincided with the earliest European mega-heatwave of the last decades causing devastating forest fires and human casualties. It was associated with an unprecedented subtropical warm air intrusion, with signatures similar to those typical of July and August ridges. Dry conditions were partially alleviated in the second half of 2017 but exacerbated again in central and northern sectors during 2018. In the case of southwestern Europe, drying abruptly ended in March 2018, when this region experienced extraordinary rainy and windy conditions following the occurrence of an exceptional Sudden Stratospheric Warming (SSW). Recent warming trends are shown to exacerbate some of these events, which may represent current examples of future European extremes. Still, the results indicate a key role of the dynamics (high-latitude blocks and subtropical ridges), whose future projections are uncertain. Future studies should address the key drivers governing regional dynamical changes that are relevant to European extremes. [ABSTRACT FROM AUTHOR]

Ships' logbooks have been preserved in archives of different European countries. This paper reviews how their records provide reliable information relevant to meteorology and climatology, extending the observational record back to at least the early 18th century. This allows describing weather during historical events, improving the knowledge on hurricanes or unveiling multidecadal variability previously unsuspected, such as the steady enhancement of the Australian monsoon, the high variability of the atmospheric circulation over the Euro‐Atlantic region during the Late Maunder Minimum or the relationship between the Western North Pacific Summer Monsoon and the El Niño—Southern Oscillation. Observations from ships can feed long‐term reanalysis projects and contribute to reduce their uncertainties over the oceans. The extended record of observations also aids the search of analogues before the human fingerprint, thus improving the detection and attribution of climate change. The integration with paleoclimate proxies is a complex task that requires merging heterogeneous records with a wide range of time resolutions, spatial density, and responses to the climate system. However, recent international efforts open the field to new opportunities. Summing up, logbooks are a consistent, but underexploited, source of relevant climatic data that will widen our knowledge of the past climate. This in turn provides a way to better understand present climatic variations and predict future changes. This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change Ships' logbooks help to understand climate variability of the last 300 years. [ABSTRACT FROM AUTHOR]

• Most of the Euro-Mediterranean region affected by drought conditions during 2021/22. • Recursive high-pressure systems & a poleward jet shift explain rainfall deficits. • Most severe drought since at least 1891 when considering evaporative demand (AED) • Enhanced AED caused unprecedented low soil moisture & runoff since at least 1965. • Potential worst-case droughts if historic rainfall deficits occur with current AED. The Euro-Mediterranean region experienced a remarkable drought during the hydrological year 2021/22. Substantial and widespread impacts on water supply systems, agricultural crops, and the production of hydroelectric power were observed. This assessment characterises the drought from a long-term perspective using a multi-index approach and analyses the associated atmospheric circulation at the annual and monthly time scales. The main dynamical forcing of the drought was the unusual recurrence of high-pressure systems over western Europe, at least partly due to an anomalous southward shift in blocking activity and a remarkable occurrence of low-latitude blocks. This led to record-breaking positive geopotential height anomalies over western Europe and a poleward displacement of the North Atlantic eddy-driven jet. Although most of the region was affected by mild drought conditions, the 2021/22 event was not unprecedented in terms of precipitation deficits since other periods of the 20th century (e.g., in the 1920s, 1940s and 1970s) displayed moderate and severe drought conditions over larger areas. However, the 2021/22 drought has been the most intense since at least 1891 because of high atmospheric evaporative demand (AED) values associated with extreme temperatures, especially during the summer of 2022. This enhanced AED also contributed to depleting soil moisture and reducing runoff generation, leading to unprecedented deficits since at least 1965. Finally, we find important differences in the 2021/22 event as compared to other major historical droughts over the Euro-Mediterranean region. In particular, the contrasting effect of AED evidences its increasing role over the last decades and warns about the current risk of experiencing unprecedented droughts. [ABSTRACT FROM AUTHOR]

Atmospheric blocking and other disruptions of the usual westerly flow are an important component of the intra-seasonal and inter-annual variability in mid-latitudes. A comprehensive assessment of high-latitude blocks and sub-tropical ridges (which do not require wave-breaking occurrence) shows that their surface impacts (temperature and precipitation) are generally of opposite signal. In particular, extreme drought episodes and heat events in southern Europe and Mediterranean-like climatic areas should not be attributed to blockings, but rather to sub-tropical ridges, as the latter almost completely wipe out precipitation and result in well above-average temperatures in these areas (Sousa et al., 2018). In this sense, a better understanding and an objective classification of sub-tropical ridges phenomenology is needed, particularly under the context of global warming, and on the hot-topic of the Hadley Cell expansion, where some contradictory results have emerged in recent years.Here we present a new algorithm designed for the detection of sub-tropical ridges. Taking advantage of this new product, we analyzed the occurrence of intense and/or persistent sub-tropical ridges in several drought and extreme heat episodes such as: the 2003 European heatwave; the 2004-2005 Iberian drought; the late 2017 wildfires season in California; the 2015-2017 "Day-Zero" drought in Cape Town. Our results show how sub-tropical intrusions were involved in these unprecedented events with significant socio-economic impacts, being the persistence and intensity of such atmospheric patterns particularly notable in western margins of continental areas (e.g. Iberia, California, South Africa). Finally, and within the context of a warming planet and the disparate rates estimated for tropical expansion (Staten et al., 2018), we have analyzed regional changes in the latitudinal extension and intensity of sub-tropical ridges. By applying the new detection scheme to the NCEP reanalysis our results suggest a clear intensification of ridges affecting areas with Mediterranean climates and its association with the observed increase in the magnitude of extreme heat and drought events in those regions. Despite the intensification of subtropical ridges, our results suggest no robust changes in its latitudinal extension at the northern hemispheric scale (when compared to internal variability). On the other hand, a more generalized poleward shift appears to be present in the southern hemisphere.Sousa et al., 2018, Climate Dynamics, DOI:10.1007/s00382-017-3620-2Staten et al., 2018, Nature Climate Change, DOI:10.1038/s41558-018-0246-2This work was supported by project IMDROFLOOD – Improving Drought and Flood Early Warning, Forecasting and Mitigation using real-time hydroclimatic indicators (WaterJPI/0004/2014) funded by FCT. [ABSTRACT FROM AUTHOR]