Search

The summer of 2022/23 in Argentina set a record with ten heatwaves. Here, we compare the synoptic and thermodynamic conditions of the four heatwaves with the largest spatial extent using ERA5 reanalysis data. All heatwaves were associated with mid-level anticyclonic anomalies but with different characteristics: three were quasi-stationary high-pressure systems, while one was transient. We also find that enhanced surface fluxes strongly influenced the daily temperature evolution. Furthermore, we perform an attribution exercise using the analogue technique to measure the contributions of atmospheric circulation, soil moisture, and climate change. For quasi-stationary events, the main contribution came from the circulation (up to 2 °C relative to random flow in the present climate). Conversely, the transient heatwave showed a stronger association with extreme soil moisture deficits, with an estimated increase of ~+1 °C relative to wetter conditions. Climate change has also increased the intensity of heatwaves by +0.5 to +1.2 °C relative to previous decades.

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.

The North Atlantic eddy-driven jet (EDJ) is an essential component of the Euro-Atlantic atmospheric circulation. It has been typically described in terms of latitude and intensity but this is not enough to fully characterize its variability and complex EDJ configurations. Here, we present a set of daily parameters of the EDJ based on low-tropospheric zonal wind data for the 1948–2020 period. They describe the intensity, sharpness, location, edges, tilt and other zonal asymmetries of the EDJ, therefore dissecting its structure beyond the latitudinal regimes. This allows for assessments of specific EDJ aspects and a multi-parametric treatment of EDJ configurations in a manageable way. Overall, variations in EDJ parameters reflect distinctive patterns of eddy forcing and wave breaking, with anticyclonic eddies playing a major role in shaping the EDJ structure. A multimodal behavior of the EDJ is only detected in latitude, which largely influences the longitudinal position of the EDJ. Other aspects of the EDJ are less constrained by the latitude and display a variety of configurations. Four multi-parametric states (northern, central, tilted and split EDJs) provide a satisfactory description of recurrent patterns of the EDJ. They participate in meridional migrations of the EDJ, but yield less dramatic transitions than viewed from the latitudinal perspective. Finally, the EDJ parameters help to better understand the EDJ influence on European climate. In many regions, latitude and intensity contain limited information on near-surface anomalies, and their signals can be masked by the additional effect of other EDJ parameters., CRUE-CSIC, Ministerio de Ciencia, Innovación y Universidades, Ministerio de Ciencia e Innovación, Depto. de Física de la Tierra y Astrofísica, Instituto de Geociencias (IGEO), Universidad Complutense de Madrid, TRUE, pub

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., Ministerio de Economía y Competitividad, Depto. de Física de la Tierra y Astrofísica, Instituto de Geociencias (IGEO), Universidad Complutense de Madrid, TRUE, pub

Recent studies have stressed the key role of the east Atlantic (EA) pattern and its interactions with the North Atlantic Oscillation (NAO) in Euro-Atlantic climate variability. However, instrumental records of these leading patterns of variability are short, hampering a proper characterization of the atmospheric circulation beyond the mid-nineteenth century. In this work, we present the longest (1685–2014) observational-based records of winter NAO and EA indices as well as estimates of the North Atlantic eddy-driven jet stream speed and latitude for the same period. The time series display large variability from interannual to multidecadal time scales, with, for example, positive (negative) EA (NAO) phases dominating before 1750 (during much of the nineteenth century). By identifying winters with different combinations of NAO/EA phases in the twentieth century, our results highlight the additional role of EA in shaping the North Atlantic action centers and the European climate responses to NAO. The EA interference with the NAO signal is stronger in precipitation than in temperature and affects areas with strong responses to NAO such as Greenland and the western Mediterranean, which prevents simplistic relationships of natural proxies with NAO. The last three centuries uncover multidecadal periods dominated by specific NAO/EA states and substantial interannual-to-centennial variability in the North Atlantic jet stream, thus providing new evidence of the dynamics behind some outstanding periods. Transitions in the NAO/EA phase space have been recurrent and pin down long-lasting anomalies, such as the displacement of the North Atlantic action centers in the late twentieth century, besides some disagreements between NAO indices., Instituto Dom Luiz, Portuguese Science Foundation, Ministerio de Economía y Competitividad, European Research Area for Climate Services, Depto. de Física de la Tierra y Astrofísica, Instituto de Geociencias (IGEO), Universidad Complutense de Madrid, TRUE, pub

Heat waves (HWs) can cause large socioeconomic and environmental impacts. The observed increases in their frequency, intensity and duration are projected to continue with global warming. This review synthesizes the state of knowledge and scientific challenges. It discusses different aspects related to the definition, triggering mechanisms, observed changes and future projections of HWs, as well as emerging research lines on subseasonal forecasts and specific types of HWs. We also identify gaps that limit progress and delineate priorities for future research. Overall, the physical drivers of HWs are not well understood, partly due to difficulties in the quantification of their interactions and responses to climate change. Influential factors convey processes at different spatio-temporal scales, from global warming and the large-scale atmospheric circulation to regional and local factors in the affected area and upwind regions. Although some thermodynamic processes have been identified, there is a lack of understanding of dynamical aspects, regional forcings and feedbacks, and their future changes. This hampers the attribution of regional trends and individual events, and reduces the ability to provide accurate forecasts and regional projections. Sustained observational networks, models of diverse complexity, narrative-based methodological approaches and artificial intelligence offer new opportunities toward process-based understanding and interdisciplinary research., EU-funded H2020 project CLINT, Ministerio de Ciencia, Innovación y Universidades, Ministerio de Economía, Industria y Competitividad, Ministerio de Ciencia e Innovación, European Research Council, Depto. de Física de la Tierra y Astrofísica, Instituto de Geociencias (IGEO), Universidad Complutense de Madrid, TRUE, pub

This study describes the climatological characteristics of regional heat waves (HWs) over southern South America (SSA) for the warm seasons (October–March) of 1979–2018 based on daily maximum temperature series from 131 weather stations. Clustering of stations with high co-occurrence of simultaneous HW days is employed to identify regional HW events over five homogeneous regions: northern, central-eastern and southern SSA regions, central Argentina, and central Chile. When all regions are considered, we find a mean frequency of ∼4 HWs per year. Transitional regions (northern SSA, central-eastern SSA and central Argentina) are characterised by longer, albeit less intense, HWs than the southernmost region (southern SSA), whereas central Chile events display the lowest duration, intensity and extension. By aggregating these single HW attributes into a combined severity index, a ranking of historical HWs has been obtained, with the March 1980 event standing as the most severe one of SSA. The assessment of long-term changes reveals significant increases in the frequency of regional HW days over central Argentina and central Chile only. Trends in HW characteristics are also region dependent, and the southernmost region is the only one where HW severity has increased significantly. We report similarities and differences in the synoptic circulation patterns associated with regional HW events. Southern SSA HWs have the most distinctive signatures, related to extratropical high-pressure systems blocking the westerly flow. In the remaining regions, HWs are associated with anomalies in the South Atlantic (northern SSA, central-eastern SSA and central Argentina) or South Pacific (central Chile) High, and the intensification of the northerly low-level flow by regional thermal lows and South American Low Level Jet events. Regional HWs often migrate from northern to central-eastern SSA and central Argentina, following the displacement/intensification of the South Atlantic High, whi, CSIC, CONICET, Universidad de Buenos Aires, Depto. de Física de la Tierra y Astrofísica, Instituto de Geociencias (IGEO), Universidad Complutense de Madrid, TRUE, pub

In 1639, the German naturalist Georg Marcgraf established the first astronomical observatory in the Americas, located in Recife (Brazil). There, he made the first daily systematic meteorological observations of wind direction, precipitation, fog, and thunder and lightning from 1640 to 1642. We outline the circumstances that led to this observatory being established and analyze the observations. The range of values obtained from all the variables recorded by Marcgraf corresponds well with Recife’s current climate. However, wetter-than-normal conditions were recorded during 1640, while anomalous concentrations of foggy days occurred from May to December 1641. We hypothesize that these anomalous record foggy days could be associated with the highly explosive eruptions of the Komagatake and Parker volcanoes, both in 1640.