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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., Comision Europea, CSIC, Portuguese Fundaç˜ ao para a Ciˆencia e a Tecnologia (FCT), Ministerio de Ciencia, Innovación y Universidades (España), Instituto Dom Luiz, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

Este proyecto propone un cambio del rol del docente en el aula de transmisor a facilitador. Para ello, se apuesta por implantar metodologías que favorezcan el aprendizaje cooperativo en el aula y potencien el desarrollo de competencias transversales.

Flash droughts (FDs) are distinguished by a rapid development associated with strong precipitation deficits and/or increases in atmospheric evaporative demand in the short-term, but little is known about the atmospheric conditions underlying these events. In this study, we analyse for the first time the atmospheric dynamics involved in the development of FDs in Spain over the period 1961–2018. FDs are related to large-scale atmospheric circulation patterns affecting the region, in particular with the positive phase of the North Atlantic Oscillation (NAO). The NAO is the main atmospheric driver of FDs in winter and autumn, and it is essential in explaining FD development in spring. We also found that FDs are typically linked to strong positive anomalies in 500 hPa geopotential height and sea level pressure over the region during the weeks prior to the onset. At the synoptic scale, the most common weather types (WTs) recorded during the development of FDs are Anticyclonic Western (ANT_W_AD), East (E_AD) and Northeast (NE_AD) advection, and Anticyclonic (ANTICYC). In particular, ANTICYC WT is the main atmospheric driver of FDs in summer. Ridging conditions occur frequently during FDs in all seasons, being the most important factor controlling FD development in spring. Likewise, we noted that some of the FDs recorded in summer are related to and/or exacerbated by Saharan air intrusions associated with pronounced ridges. The results of this research have important implications for the understanding, monitoring and prediction of FDs in Spain, providing a detailed assessment of the main atmospheric dynamics involved in FD triggering at different spatial scales., Ministerio de Ciencia, Innovación y Universidades (España), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub, Pagado por el autor

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

The upper-level jet stream is a critical element of atmospheric circulation, driving synoptic systems and extreme weather events. This study analyzes the impact of upper-level jets on South American (SA) summer temperature and precipitation under different El Niño-Southern Oscillation (ENSO) phases. Using the ERA5 reanalysis dataset from 1979 to 2022, we perform a daily multiparametric characterization of the jet stream, considering its spatial and temporal discontinuities. Besides latitude and intensity, we find that the departure and number of branches of the subtropical jet (STJ) and the longitudinal extent of the Pacific branch of the polar front jet (PFJ) are needed for their description. An additional parameter is required to characterize the STJ due to its absence on around 40% of summer days over SA. Moreover, we observe distinct long-term changes in PFJ parameters across different ocean basins. Three synoptic weather types (WTs) of the upper-level zonal wind are identified: normal conditions, a prominent STJ pattern, and a PFJ-only pattern. The latter pattern is associated with anticyclonic anomalies at 500hPa in the South Atlantic Ocean and an active SA Convergence Zone, which favors clear skies and warm (wet and cold) conditions in southern SA (Brazil). Consistently, the probability of experiencing warm spells in central Argentina is increased more than twofold. Finally, we detect that the temperature anomalies associated with the WTs are independent of the ENSO phase. However, ENSO modulates the frequency of the WTs: during La Niña (El Niño), the PFJ-only (prominent STJ) pattern is more common., Unión Europea. H2020, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

This paper assesses whether moving summer holidays to the warmest period of the year in Spain could be a useful climate change adaptation strategy. While the most popular period for Spanish summer holidays has traditionally been August, we illustrate that the second half of July is the hottest period of the year and when the negative effects of high temperatures are most pronounced. If the holiday period in the second fortnight of August was moved to the second fortnight of July, some of the associated impacts would be mitigated due to the reduced anthropogenic activity during non-working days. In particular, we find a significant reduction in the annual peak of labour productivity loss (~25 %) and, to a lesser extent, of electricity demand and near-surface ozone concentrations (~3–4 %). Finally, we also show that global warming could lead to enhanced differences between both fortnights (even with no change in the seasonal cycle of temperature) because of the non-linear relationships between temperature and its impacts. Therefore, the positive effect of shifting holidays would be even larger in the coming future., Ministerio de Ciencia e Innovación, Comisión Europea, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

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., Ministerio de Economía, Industria y Competitividad, Ministerio de Ciencia Innovación y Universidades, Ministerio de Educación, Cultura y Deporte, National Science Foundation, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

The build-up of pollutants to harmful levels can occur when meteorological conditions favour their production or accumulation near the surface. Such conditions can arise when a region experiences air stagnation. The link between European air stagnation, air pollution and the synoptic- to large-scale circulation is investigated in this article across all seasons and the 1979–2018 period. Dynamical indices identifying atmospheric blocking, Rossby wave breaking, subtropical ridges, and the North Atlantic eddy-driven and subtropical jets are used to describe the synoptic- to large-scale circulation as predictors in statistical models of air stagnation and pollutant variability. It is found that the large-scale circulation can explain approximately 60 % of the variance in monthly air stagnation, ozone and wintertime particulate matter (PM) in five distinct regions within Europe. The variance explained by the model does not vary strongly across regions and seasons, apart from for PM when the skill is highest in winter. However, the dynamical indices most related to air stagnation do depend on region and season. The blocking and Rossby wave breaking predictors tend to be the most important for describing air stagnation and pollutant variability in northern regions, whereas ridges and the subtropical jet are more important to the south. The demonstrated correspondence between air stagnation, pollution and the large-scale circulation can be used to assess the representation of stagnation in climate models, which is key for understanding how air stagnation and its associated climatic impacts may change in the future., Ministerio de Economía, Industria y Competitividad, Ministerio de Ciencia, Innovación y Universidades, Comunidad de Madrid, Ministerio de Educación, Cultura y Deporte, Ministerio de Economía y Competitividad, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

Air stagnation occurs under stable weather conditions, weak winds in the lower tomid-troposphere and absence of precipitation. These conditions minimize the horizontal dispersion and vertical mixing of air masses as well as the scavenging of air pollutants, favouring their accumulation in the lower atmospheric layers (e.g. Leibensperger et al.,2008; Jacob and Winner, 2009; Tai et al., 2010; Dawson et al., 2014). In the last few years, several studies have developed meteorological indices to identify stagnant conditions conducive to enhanced air pollution (Wang and Angell, 1999;Horton et al., 2012, 2014; Wang et al., 2016, 2018; Cai et al., 2017; Zou et al., 2017; Feng et al., 2018, 2020; Huang et al., 2018). Despite sharing common features, such socalled air stagnation indices (ASIs) are defined based on different meteorological variables and their applicability may be geographically dependent. Most previous studies on air stagnation have either been conducted on global and hemispheric scales (Horton et al.,2012, 2014; Wang et al., 2018), or have been confined to the US (Wang and Angell, 1999; Leibensperger et al., 2008; Tai et al., 2010) or China (Huang et al., 2017, 2018; Wanget al., 2016; Zou et al., 2020). However, although southern Europe has been identified as a climate hot spot where climate models project strong increases in air stagnation frequency (Horton et al., 2014), a systematic analysis of air stagnation and its impact on air quality has not been carried out hitherto for Europe and the Mediterranean region...

Air stagnation occurs under stable weather conditions, weak winds in the lower tomid-troposphere and absence of precipitation. These conditions minimize the horizontal dispersion and vertical mixing of air masses as well as the scavenging of air pollutants, favouring their accumulation in the lower atmospheric layers (e.g. Leibensperger et al.,2008; Jacob and Winner, 2009; Tai et al., 2010; Dawson et al., 2014). In the last few years, several studies have developed meteorological indices to identify stagnant conditions conducive to enhanced air pollution (Wang and Angell, 1999;Horton et al., 2012, 2014; Wang et al., 2016, 2018; Cai et al., 2017; Zou et al., 2017; Feng et al., 2018, 2020; Huang et al., 2018). Despite sharing common features, such socalled air stagnation indices (ASIs) are defined based on different meteorological variables and their applicability may be geographically dependent. Most previous studies on air stagnation have either been conducted on global and hemispheric scales (Horton et al.,2012, 2014; Wang et al., 2018), or have been confined to the US (Wang and Angell, 1999; Leibensperger et al., 2008; Tai et al., 2010) or China (Huang et al., 2017, 2018; Wanget al., 2016; Zou et al., 2020). However, although southern Europe has been identified as a climate hot spot where climate models project strong increases in air stagnation frequency (Horton et al., 2014), a systematic analysis of air stagnation and its impact on air quality has not been carried out hitherto for Europe and the Mediterranean region..., El estancamiento atmosférico se caracteriza por condiciones atmosféricas estables, vientos débiles en la troposfera media y baja, y ausencia de precipitación. Estas condiciones minimizan la dispersión horizontal y la mezcla vertical de masas de aire, favoreciendo la acumulación de contaminantes cerca de la superficie de la Tierra (ej. Leibensperger et al., 2008; Jacob and Winner, 2009; Tai et al., 2010; Dawson et al., 2014). En los últimos años, varios estudios han desarrollado índices meteorológicos para identificar las condiciones de estancamiento que podrían desencadenar episodios de contaminación atmosférica (Wang and Angell, 1999; Horton et al., 2012, 2014; Wang et al.,2016, 2018; Cai et al., 2017; Zou et al., 2017; Feng et al., 2018, 2020; Huang et al., 2018). Pese a compartir características comunes, estos índices se definen a partir de diferentes variables meteorológicas y su aplicabilidad podría depender del lugar. En el momento actual, la mayoría de los estudios sobre las situaciones de estancamiento se han realizado a escala global o hemisférica (Horton et al., 2012, 2014; Wang et al., 2018) o se han centrado en los Estados Unidos (Wang and Angell, 1999; Leibensperger et al., 2008; Tai et al., 2010)y China (Huang et al., 2017, 2018; Wang et al., 2016; Zou et al., 2020). Sin embargo, pese a que las proyecciones climáticas indican que el entorno Mediterráneo podría ser una delas zonas con un mayor aumento del estancamiento en el futuro (Horton et al., 2014), no se ha llevado a cabo un análisis sistemático sobre el mismo para esta región...

El archivo adjunto es el último manuscrito enviado a la revista antes de ser publicado (posprint)., We have assessed the dependency of wind power resources in Western Europe on the atmospheric circulation as represented by a new set of 8 tailored weather regimes (WRs). For this purpose, we have derived wind capacity factors (CFs) from a meteorological reanalysis dataset and from high-resolution data simulated by the Weather Research and Forecasting (WRF) model. We first show that WRs capture effectively year-round onshore wind power production variability across Europe, especially over northwestern/central Europe and Iberia. Since the influence of the large-scale circulation on wind energy production is regionally dependent, we have then examined the high-resolution CF data interpolated to the location of more than 100 wind farms in two regions with different orography and climatological features, the United Kingdom and the Iberian Peninsula. The use of the monthly frequencies of occurrence of WRs as predictors in a multi-linear regression model allows explaining up to two thirds of the month-to-month CF variability for most seasons and sub-regions. These results outperform those previously reported based on Euro-Atlantic modes of atmospheric circulation, indicating that the use of WRs customized to the region of study is preferred to reproduce the evolution of wind energy resources. Finally, we have applied these WRs to understand the day-to-day evolution of specific episodes with anomalous regional wind power production. In particular, the wind energy deficit of summer 2018 in the United Kingdom and the surplus of March 2018 in Iberia stemmed from the combination of WRs associated with low and high CFs, respectively. These findings are relevant for the forecast of wind energy resources as the large-scale features of the atmospheric circulation captured by WRs can be modelled with considerably less uncertainty than wind speeds at wind farm sites., Iberdrola Renovables Energía S.A.U, Ministerio de Educación, Cultura y Deporte, Ministerio de Economía y Competitividad, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

El archivo adjunto es el último manuscrito enviado a la revista antes de ser publicado (posprint)., We have examined the joint impact of daily maximum temperature and air stagnation on observed maximum daily 8-h running average (MDA8) and hourly near-surface ozone (O3) over eight regions of Europe for the summer period 1998–2015. The percentage of stagnant area in a region is a better predictor of summer MDA8 O3 in central/southern Europe (correlation coefficient R = 0.50–0.70) than in the north (R = 0.06–0.39). The correlations of MDA8 O3 with temperature are higher than with stagnation for most regions, and the impact of stagnation on those correlations is region-dependent. MDA8 O3 mixing ratios consistently increase over central/southern Europe under stagnant conditions, but this has not been found for some temperature ranges in the north. Under non-stagnant situations and relatively high temperatures (20–25 °C), southerly advection often brings aged air masses from more polluted areas to the receptor regions in the north. Furthermore, the occurrence of stagnation tends to amplify the ozone diurnal cycles in the center/south of the continent, yielding lower nighttime and higher daytime mixing ratios than on non-stagnant days, again with a less clear effect in the north. Changes in planetary boundary layer height, accumulation of ozone and precursors, and subsequent photochemical production during stagnant days are the presumed underlying mechanisms for the amplification of the diurnal cycles. The results from this study prove that the effects of stagnation on summer ozone are regionally dependent across Europe. Consequently, climate model projections of increases in stagnation should not directly be translated into degraded air quality without a proper assessment of the regional impacts., Ministerio de Educación, Cultura y Deporte, Ministerio de Economía y Competitividad, Ministerio de Economía, Industria y Competitividad, Ubben Program for Climate and Carbon Science, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

This Ph.D. Thesis elaborates and analyzes several hybrid Soft-Computing algorithms for optimization and prediction problems in Atmospheric Physics. The core of the Thesis is a recently developed optimization meta-heuristic, the Coral Reefs Optimization Algorithm (CRO), an evolutionary-based approach which considers a population of possible solutions to a given optimization problem. It simulates different procedures mimicking real processes occurring in coral reefs in order to evolve the population towards good solutions for the problem. Alternative modifications of this algorithm lead to powerful co-evolution meta-heuristics, such as theCRO-SL, in which Substrates implementing different search procedures are included. Another modification of the algorithm leads to the CRO-SP, which considers Species in the evolutionof the population, and it is able to deal with different encodings within a single population.These approaches are hybridized with other Machine Learning and traditional algorithms such as neural networks or the Analogue Method (AM), to come up with powerful hybrid approaches able to solve hard problems in Atmospheric Physics...

This Ph.D. Thesis elaborates and analyzes several hybrid Soft-Computing algorithms for optimization and prediction problems in Atmospheric Physics. The core of the Thesis is a recently developed optimization meta-heuristic, the Coral Reefs Optimization Algorithm (CRO), an evolutionary-based approach which considers a population of possible solutions to a given optimization problem. It simulates different procedures mimicking real processes occurring in coral reefs in order to evolve the population towards good solutions for the problem. Alternative modifications of this algorithm lead to powerful co-evolution meta-heuristics, such as theCRO-SL, in which Substrates implementing different search procedures are included. Another modification of the algorithm leads to the CRO-SP, which considers Species in the evolutionof the population, and it is able to deal with different encodings within a single population.These approaches are hybridized with other Machine Learning and traditional algorithms such as neural networks or the Analogue Method (AM), to come up with powerful hybrid approaches able to solve hard problems in Atmospheric Physics..., En esta Tesis Doctoral se elaboran y analizan en detalle diferentes algoritmos híbridos deSoft-Computing para problemas de optimización y predicción en Física de la Atmósfera. El núcleo central de la Tesis es un algoritmo meta-heurístico de optimización recientemente desarrollado, conocido como Coral Reefs Optimization algorithm (CRO). Este algoritmo pertenece a la familia de la Computación Evolutiva, de forma que considera una población de solucionesa un problema concreto, y simula los diferentes procesos que ocurren en un arrecife de coralpara evolucionar dicha población hacia la solución óptima del problema. Recientemente se han propuesto diferentes versiones del algoritmo CRO básico para obtener mecanismos potentes de optimización co-evolutiva. Una de estas modificaciones es el CRO-SL, en la que se definen un conjunto de Sustratos en el algoritmo, de manera que cada sustrato simula un mecanismo de evolución diferente, que son aplicados a la vez en una única población. Otra modificación hadado lugar al conocido como CRO-SP, un algoritmo donde se definen diferentes Especies, capaz de manejar varias codificaciones para un mismo problema a la vez. Estas versiones del CRO han sido hibridadas con varias técnicas de Aprendizaje Máquina, tales como varios tipos de redes neuronales de entrenamiento rápido, sistemas de aprendizaje tales como Máquinas de Vectores Soporte, o sistemas de predicción vinculados totalmente al área de la Física Atmosférica, tales como el Método de los Análogos (AM). Los algoritmos híbridos obtenidos son muy robustos y capaces de obtener excelentes soluciones en diferentes problemas donde han sido probados...

Droughts are probably the natural hazard with the highest socioeconomicimpact. Simultaneously, they are a very complex phenomenon; they are triggered by a diversity of physical factors and occur at a variety of time scales. Consequently, the instrumental record currently available is too short and the characterization of its multidecadal variability requires the use of natural proxies (tree rings, sedimentary records) or documentary sources. In this paper we analyse three documentary sources with potential to analyse the long-term variability of droughts: chapter acts, logbooks and chronicles. The chapter acts recorded discussions and decisions made during the assemblies of the local authorities and provide continuous and direct evidence on drought impacts. They are especially useful to study droughts between the 15th and the 19th centuries in Europe and the 17th to 18th in the former colonies. Logbooks recorded the meteorological conditions and the incidents occurred during navigation. They provide indirect information through the circulation indices that can be very helpful to understand the mechanisms and teleconnections associated to droughts. Finally, the chronicles are historiographical documents describing political and social events. They are secondary sources and the references to climatic events are discontinuous, thus their analysis must be extremely careful, but they are especially useful to study specific drought events especially prior to 15th century when no other sources are available., Las sequías son uno de los riesgos naturales que mayor impacto causan en la población y en la economía, por lo que estudiarlas es fundamental para poder implementar medidas de prevención y adaptación a las mismas. Sin embargo, son un fenómeno climático muy complejo que ocurre a distintas escalas temporales y se desencadena por una amplia variedad de factores físicos. El registro instrumental del que se dispone actualmente no es suficientemente largo para estudiar en detalle las sequías, especialmente su variabilidad multidecadal por lo que se hace necesario recurrir a otras fuentes de información como los proxies naturales (anillos de los árboles, registros sedimentarios…) o las fuentes documentales. En este trabajo analizamos tres fuentes documentales con potencial en el estudio de la variabilidad multidecadal de las sequías: actas capitulares, diarios de navegación y crónicas. Las actas capitulares registran las discusiones y decisiones tomadas por los gobiernos locales en sus reuniones. Destacan debido a que proporcionan información continua y directa sobre los impactos de las sequías y son de especial relevancia entre los siglos XV y XIX en Europa y en los siglos XVII y XVIII en las colonias. Los diarios de navegación son los registros que elaboran los navegantes durante sus rutas, en los que registran las condiciones meteorológicas de las mismas y los incidentes ocurridos. Presentan información indirecta de índices de circulación especialmente interesantes para entender los mecanismos y teleconexiones asociados a las sequías. Por último, las crónicas son documentos historiográficos que se realizan con el objetivo de describir eventos políticos y sociales. Sin embargo, se trata de fuentes documentales secundarias, donde las referencias a eventos climáticos son discontinuas. Por ello, deben ser tratadas con cautela. Las crónicas no son de gran utilidad para estudiar la variabilidad de las sequías, no obstante pueden ser muy útiles para estudiar eventos de sequía

The Northern Hemisphere annular mode, also known as the Arctic Oscillation/North Atlantic Oscillation (AO/NAO) is a dominant atmospheric mode in the Northern Hemisphere winter that influences climate fluctuations from the eastern seaboard of the United States to Siberia and from the Arctic to the subtropical Atlantic. After almost a century of scientific investigation, the fundamental mechanisms determining the evolution of the AO/NAO are not yet completely understood. The ocean is favored as the most likely forcing of atmospheric variability, given the time scales of oceanic circulation and its large heat capacity. Our analyses of snow cover, soil temperatures, zonal winds, and geopotential heights identify the effect of land–atmosphere interaction over Eurasia on Northern Hemisphere atmospheric circulation, explaining the predictive signal that links fluctuations of April–October snow cover with the following winter AO/NAO phases.

Southwestern Europe experienced extraordinary rainy and windy conditions in March 2018, leading to the end of the most severe drought since 1970 at continental scale. This anomalous weather was linked to a persistent negative North Atlantic Oscillation pattern. Two weeks earlier a sudden stratospheric warming (SSW) took place, preceded by the strongest planetary wave activity on record. In this study, we explore the connection between the SSW and the weather shift by employing a weather regime approach and flow analogues. The timing of the downward propagation of the stratospheric anomalies, the transition to and persistence of the negative North Atlantic Oscillation weather regime, and the sudden precipitation increase are all consistent with the typical tropospheric state after SSWs. Our results evidence a significant role of the 2018 SSW in the record-breaking precipitation event., Unión Europea - FP7, Ministerio de Economía, Comercio y Empresa (España), Programme Atracción de Talento de la Comunidad de Madrid, Ministerio de Educación, Formación Profesional y Deportes (España), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub