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This paper reports analysis of the ability of 24 coupled global climate models that were used in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change to simulate the current monthly seasonal cycle of sea level pressure, surface air temperature and precipitation over the Iberian Peninsula in the last two decades of the twentieth century. The period investigated runs from 1979 to 1998. In order to assess the performance of the models, averaged seasonal cycles and probability density functions (PDFs) calculated from model simulations are compared with the corresponding seasonal cycles, whilst PDFs are also obtained using the data from the ERA40 reanalysis and the Global Precipitation Climatology Project. We found that simulated PDFs generally provided a better fit to actual PDFs than seasonal cycles do. This conclusion indicates that when evaluating model performance, the climate variability as measured by means of PDFs is not the only climatic element that should be tested. Regarding the comparison based on the seasonal cycle, results also show that the root mean square skill score is more useful than the r skill score. To rank the AR4 models, sea level pressure, surface air temperature and precipitation variables were selected and a group of five AR4 models were identified as the models which best reproduce current climate in the area: MIROC3.2-HIRES, MPI-ECHAM5, GFDL-CM2.1, BCCR-BCM2.0 and UKMO-HADGEM1. The rank obtained should not be understood in a hierarchical manner because there is a certain degree of internal variability in the model ensembles. Finally, it should be noted that these results are in good agreement with other classifications found in the scientific literature. [ABSTRACT FROM AUTHOR]

Precipitation over the Western part of Iberian Peninsula is known to be related to the large-scale sea level pressure field and thus to advection of humidity into this area. The major problem is to downscale this synoptic atmospheric information to local daily precipitation patterns. One way to handle this problem is by weather-state models, where, based on the pressure field, each day is classified into a weather state and precipitation is then modeled within each weather state via multivariate distributions. In this paper, we propose a spatiotemporal Bayesian hierarchical model for precipitation. Basic objective and novelty of the paper is to capture and model the essential spatiotemporal relationships that exist between large-scale sea level pressure field and local daily precipitation. A specific local spatial ordering that mimics the essential large-scale patterns is used in the likelihood. The model is then applied to a network of rain gauge Stations in the river Tagus valley. The inference is then carried out using appropriate MCMC methods. [ABSTRACT FROM AUTHOR]

The North Atlantic Oscillation (NAO) exerts a major influence on the climate of the North Atlantic region. However, other atmospheric circulation modes (ACMs), such as the East Atlantic (EA) and Scandinavian (SCAND) patterns, also play significant roles. The dynamics of lakes on the Iberian Peninsula are greatly controlled by climatic parameters, but their relationship with these various ACMs has not been investigated in detail. In this paper, we analyze monthly meteorological and limnological long-term datasets (1950-2011 and 1992-2011, respectively) from two lakes on the northern and central Iberian Peninsula (Sanabria and Las Madres) to develop an understanding of the seasonal sensitivity of these freshwater systems to the NAO, EA and SCAND circulation modes. The limnological variability within Lake Sanabria is primarily controlled by fluctuations in the seasonal precipitation and wind, and the primary ACMs associated with the winter limnological processes are the NAO and the SCAND modes, whereas only the EA mode appears to weakly influence processes during the summer. However, Lake Las Madres is affected by precipitation, wind and, to a lesser extent, temperature, whereas the ACMs have less influence. Therefore, we aim to show that the lakes of the Iberian Peninsula are sensitive to these ACMs. The results presented here indicate that the lake dynamics, in some cases, have a higher sensitivity to variations in the ACMs than single local meteorological variables. However, certain local features, such as geography, lake morphology and anthropic influences, are crucial to properly record the signals of these ACMs. [ABSTRACT FROM AUTHOR]

The aim of this paper is to quantitatively characterize the climatology of daily precipitation indices in Catalonia (northeastern Iberian Peninsula) from 1951 to 2003. This work has been performed analyzing a subset of the ETCCDI (Expert Team on Climate Change Detection and Indices) precipitation indices calculated from a new interpolated dataset of daily precipitation, namely SPAIN02, regular at 0.2° horizontal resolution (around 20 km) and from two high-quality stations: the Ebro and Fabra observatories. Using a jack-knife technique, we have found that the sampling error of the SPAIN02 regional averaged is relatively low. The trend analysis has been implemented using a Circular Block Bootstrap procedure applicable to non-normal distributions and autocorrelated series. A running trend analysis has been applied to analyze the trend persistence. No general trends at a regional scale are observed, considering the annual or the seasonal regional averaged series of all the indices for all the time windows considered. Only the consecutive dry days index (CDD) at annual scale shows a locally coherent spatial trend pattern; around 30 % of the Catalonia area has experienced an increase of around 2-3 days decade-1. The Ebro and Fabra observatories show a similar CDD trend, mainly due to the summer contribution. Besides this, a significant decrease in total precipitation (around -10mm decade-1) and in the index "highest precipitation amount in five-day period" (RX5DAY, around -5 mm decade-1), have been found in summer for the Ebro observatory. [ABSTRACT FROM AUTHOR]

In this paper, series of drought occurrence and drought extension in the Iberian Peninsula are constructed for the 1600-1750 period from seven rogation series. These rogation ceremony records come from Bilbao, Catalonia, Zamora, Zaragoza, Toledo, Murcia and Seville. They are distributed across the Peninsula and include the areas with the most characteristic Iberian climate types, influenced by the Atlantic and the Mediterranean conditions, described from modern data. A seasonal division of the series shows that spring is a critical season for rogation series in most of Iberia, being Bilbao the only site were the highest number of rogations is detected for a different season. The annual analysis of the series shows a dramatic difference between the first half of the 17th century when droughts are characterized by its local character; and the rest of the period, when they affect to broader regions or even to the whole Peninsula. The analysis of spring series confirms the existence of the two periods detected in the annual analysis. Finally, secondary documentary sources are used to further characterise the two most extended droughts in the period, 1664 and 1680, and to verify the extension of the areas affected by droughts recorded through rogation series. [ABSTRACT FROM AUTHOR]

This paper studies the winter temperatures of the second part of the sixteenth century in the central area of the Iberian Peninsula. A large number of historical documents that are stored in many different Spanish archives were consulted in order to carry out this research. The data was first arranged and weighted according to the intensity and significance of the meteorological phenomena described and, subsequently, these values were assigned an ordinal index ranging from +4 to -4. The statistical treatment applied is based on the reconstruction of temperatures equivalent to this ordinal index, expressed as anomalies of the 1961-1990 period, belonging to a reference station located at the approximate geographical center of the area under study. The results show winter thermal conditions different from current ones that, for the most part, stay below the reference average and that occurred with a wide range of variability. The influence that thermal conditions had on the evolution of some environmental aspects are considered based on the forest exploitation problem information and on the wine harvest production. [ABSTRACT FROM AUTHOR]

The interannual variability and predictability of the winter streamflow of the main Iberian Peninsula international rivers (Douro, Tejo, and Guadiana) are examined for the period 1923–2004. In the first part of this paper, a singular spectral analysis was carried out to isolate the main oscillatory components of the streamflow series. Results showed a similar model structure for the three rivers, including the following components: (i) a nonlinear trend that contains variability at periods of 20–30 yr, (ii) modulated amplitude oscillations with associated periods in the bands 2–3, 4–5, and 6–8 yr, and (iii) a red noise process. These models accounts for the bulk of winter river flow variance, ranging between 64% (Guadiana) and 96% (Douro). In general, the amount of variability associated with the low-frequency component is similar to that associated with the interannual variability. The analysis of the association between the North Atlantic Oscillation (NAO) and the streamflow variability proved this relationship to be complex and nonstationary. In particular, it is found that only when the NAO presents high amplitude oscillations is this mode capable of dominating the streamflow variability. In Part II, autoregressive-moving-average (ARMA) models were fitted to the filtered streamflow series and an interannual forecasting experiment was conducted. Results were tested against the raw streamflow series. The percentage of variance explained by the models ranged from 25% to 62%. Additionally, the ARMA models presented useful one-year-ahead forecasting skills. Particularly during the validation period (1986–2004) the models performed between 51% and 53% better than climatology. The skill against persistence proved to be much greater, indicating that the climatology is a better benchmark than persistence for streamflow forecasting in Iberia. Finally, the developed models were, in most cases, able to accurately predict the phase of the streamflow, with a percentage of agreement that ranged from 54% to 90% throughout the validation period. [ABSTRACT FROM AUTHOR]

• Long-term air temperature prediction is carried out by a novel two-phased approach. • eXplainable Artificial Intelligence models are applied to better analyse the results. • The approach is applied to the Southern part of the Iberian Peninsula from ERA5 data. • A comprehensive comparison against state-of-the-art techniques has been carried out. • XAI models outperform the compared techniques and benefit from being interpretable. In this paper we have tackled the problem of long-term air temperature prediction with eXplainable Artificial Intelligence (XAI) models. Specifically, we have evaluated the performance of an Artificial Neural Network (ANN) architecture with sigmoidal neurons in the hidden layer, trained by means of an evolutionary algorithm (Evolutionary ANNs, EANNs). This XAI model architecture (XAI-EANN) has been applied to the long-term air temperature prediction at different sub-regions of the South of the Iberian Peninsula. In this case, the average August air temperature has been predicted from ERA5 Reanalysis data variables, obtaining good predictions skills and explainable models in terms of the input climatological variables considered. A cluster analysis has been first carried out in terms of the average air temperature in the zone, in such a way that a number of sub-regions with different air temperature behaviour have been defined. The proposed XAI-EANN model architecture has been applied to each of the defined sub-regions, in order to find significant differences among them, which can be explained with the XAI-EANN models obtained. Finally, a comprehensive comparison against some state-of-the-art techniques has also been carried out, concluding that there are statistically significant differences in terms of accuracy in favour of the proposed XAI-EANN model, which also benefits from being an XAI model. [ABSTRACT FROM AUTHOR]

A high resolution atmospheric modelling study was done for a 20-year recent historical period. The dynamic downscaling approach adopted used the Max Planck Institute Earth System Model (MPI-ESM) to drive the WRF running in climate mode. Three online nested domains were used covering part of the North Atlantic and Europe, with a resolution 81 km, and reaching 9 km in the innermost domain which covers the Iberian Peninsula. This paper presents the validation of the WRF configuration, which is based on historic simulations between 1986 and 2005 and observational datasets of near surface temperature and precipitation for the same period. The validation was done in terms of comparison of probability distributions between model results and observations, as daily climatologies, spatially averaged inside subdomains obtained with cluster analysis of the observations, for each of the four seasons. In addition, Taylor diagrams are presented for each of the seasons and subdomains. This validation approach was repeated with the results of a new WRF simulation with the same parameterisations but forced by the ERA-Interim reanalysis. The capacity of the MPI-ESM driven WRF configuration to compare with observations and in a manner similar to the ERA-Interim driven WRF, ensures the capacity of the configuration for climate and climate change studies. Considering the difficulty to simulate extremes in long term simulations, the results showed a comfortable comparison of both models (forced by climate model and reanalysis results) with observations. This provides us confidence on the continuity of using the MPI-ESM driven WRF configuration for climate studies. [ABSTRACT FROM AUTHOR]

Available research has extensively examined the spatiotemporal patterns of fire‐weather regime in Portugal, but a comprehensive climatology of extreme wildfires is still under development. This study calls for different strategies and scales of analysis aiming to describe the relationships between medium and low troposphere weather conditions and severe fire behaviour in mainland Portugal, between 1980 and 2018. In particular, critical fire‐weather patterns and thresholds that can contribute to operational and forecasting know‐how in short and medium time ranges are presented. We updated the general trends in the fire regime with a new, longer daily burned area series and developed a method that identifies Extreme Wildfire Periods (EWP) that form the basis for climate analysis. Synoptic analysis using Circulation Weather Types (CWT) showed that the northeasterly and easterly directional flows are significantly associated with EWP and produce the most severe fire‐weather conditions. The four main CWT related to extreme fire are driven from anticyclones over the eastern Atlantic between the Azores and the British Isles. However, severe situations can also be regulated by CWT with marginal presence in both summer and EWP: low systems located to the west and northwest of Iberia carrying air masses from the south quadrant are related to catastrophic events. Regarding the antecedent climate, the results indicate that the coincident meteorological drought, whether weak or intense, is a necessary but not sufficient condition for the development of an EWP. An increasing relevance of water stress for shorter intervals preceding EWP, in the order of days and weeks, is apparent. Following these results, fine dead fuel moisture thresholds related to transitions in fire behaviour in Portuguese landscapes are computed using a promising predictive moisture content model. Finally, the different methods used are summoned for the detailed analysis of an EWP starting under unusual synoptic circulation. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim To understand how vegetation mediates the interplay between fire and climate. Specifically, we predict that neither the switching of climatic conditions to high flammability nor the sensitivity of fire to such conditions are universal, but rather depend on fuel (vegetation) structure, which in turn changes with productivity. Location An aridity/productivity gradient on the Iberian Peninsula (Mediterranean Basin). Methods We defined 13 regions distributed along an aridity gradient, which thus differ in productivity and fuel structure. We then assessed the changes in the temporal fire-climate relationship across regions. Specifically, for each region we estimated three variables: the aridity level for switching to flammable conditions (i.e. climatic conditions conducive to fire), the frequency of these flammable conditions and the area burnt under such conditions. These variables were then related to regional aridity and fuel structure indicators. Results In mediterranean ecosystems, the aridity level for switching to flammable conditions increased along the aridity gradient. Differences in fire activity between regions were not explained by the frequency of flammable conditions but by the sensitivity of fire to such conditions, which was higher in wetter and more productive regions. Main conclusions Under mediterranean climatic conditions, fuel structure is more relevant in driving fire activity than the frequency of climatic conditions conducive to fire. At a global scale, fuel also drives the fire-climate relationship because it determines the climatic (aridity) threshold for switching to flammable conditions. Our results emphasize the role of landscape structure in shaping current and future fire-climate relationships at a regional scale, and suggest that future changes in the fire regime (i.e. under global warming) might be different from what it is predicted by climate alone. [ABSTRACT FROM AUTHOR]

This study presents the monthly 10‐m wind speed climatology, decadal variability and possible trends in the North Atlantic and Europe from ERA5 reanalysis from 1979 to 2018 and investigates the physical reasons for the decadal variability. Additionally, temporal time series are examined in three locations: the central North Atlantic, Finland and Iberian Peninsula. The 40‐year mean and the 98th percentile wind speeds emphasize a distinct land‐sea contrast and a seasonal variation with the strongest winds over the ocean and during winter. The strongest winds and the highest variability are associated with the storm tracks and local wind phenomena such as the mistral. The extremeness of the winds is examined with an extreme wind factor (the 98th percentile divided by mean wind speeds) which in all months is higher in southern Europe than in northern Europe. Mostly no linear trends in 10‐m wind speeds are identified in the three locations but large annual and decadal variability is evident. The decadal 10‐m wind speeds were stronger than average in the 1990s in northern Europe and in the 1980s and 2010s in southern Europe. These decadal changes were largely explained by the positioning of the jet stream and storm tracks and the strength of the north–south pressure gradient in the North Atlantic. The 10‐m winds have a positive correlation with the North Atlantic Oscillation in the central North Atlantic and Finland on annual scales and during cold season months and a negative correlation in Iberian Peninsula mostly from July to March. The Atlantic Multi‐decadal Oscillation has a moderate negative correlation with the winds in the central North Atlantic but no correlation in Finland and Iberian Peninsula. Overall, our results emphasize that while linear trends in wind speeds may show a general long‐term trend, more information on the changes is obtained by analysing long‐term variability. [ABSTRACT FROM AUTHOR]

The realism of a specific configuration of the WRF Regional Climate Model (RCM) to represent the observed temperature evolution over the Iberian Peninsula (IP) in the 1971–2005 period has been analyzed. The E-OBS observational dataset was used for this purpose. Also, the added value of the WRF simulations with respect to the IPSL Earth System Model (ESM) used to drive the WRF RCM was evaluated. In general, WRF presents lower temperatures than in the observations (negative biases) over the IP. These biases are comparatively larger than those of the driving ESM. Once the biases are corrected, WRF provides an added value in terms of a higher spatial representation. WRF introduces more variability in some regions in comparison to gridded observation. Warming trends according to the observations are also well represented by the RCM. In the second part of this study, the projections of future climate performed with both the ESM and the RCM were evaluated for the RCP4.5 and RCP8.5 scenarios during the 21st century. Although both models simulate temperature increases, the RCM simulates a smaller warming than the ESM after the mid-21st century, except for winter. Using the WRF model, the maximum temperature increase reaches 6 ∘ C and 3 ∘ C for RCP8.5 and RCP4.5 in the south east of the Iberian Peninsula by the end of the 21st century, respectively. [ABSTRACT FROM AUTHOR]

Climate change projections for the four major divisions of the Worldwide Bioclimatic Classification System in the Iberian Peninsula (IP) are analysed using a six‐member ensemble (EURO‐CORDEX) for 1961–1990, 1981–2010, 2011–2040, and 2041–2070 periods for RCP4.5 and RCP8.5. The direct forcing method was used to correct the bias of the simulated data using an observational gridded dataset (E‐OBS). Results show a decrease of the temperate areas in the north‐western region of the IP, with higher expression in RCP8.5 for 2041–2070. Major changes in bioclimates, ombrotypes, and thermotypes are projected to occur in northernmost regions, as well as, central and south‐eastern areas of Iberia. The projected decrease of Mediterranean pluviseasonal areas hint at a decrease of several evergreen or deciduous forest types. Conversely, due to the projected increase of Mediterranean xeric and desertic areas, it can be expected an increase of microforests or dense shrubby lands, as well as the appearance of half deserts or low‐density scrublands. Finally, the continentality index patterns revealed a strengthening of the coastal‐inner climate contrasts in the future, mainly for RCP8.5. [ABSTRACT FROM AUTHOR]

The authors present a novel self-organized climate regionalization (CR) method that obtains a spatial clustering of regions, based on the explained variance of physical measurements in their coverage. This method enables a microscopic characterization of the probabilistic spatial extent of climate regions, using the statistics of the obtained clusters. It also allows for the study of the macroscopic behaviour of climate regions through time by using the dissimilarity among different cluster size probability histograms. The main advantages of the presented method, based on the Second-Order Data-Coupled Clustering (SODCC) algorithm, are that SODCC is robust to the selection of tunable parameters and that it does not require a regular or homogeneous grid to be applied. Moreover, the SODCC method has higher spatial resolution, lower computational complexity, and allows for a more direct physical interpretation of the outputs than other existing CR methods, such as Empirical Orthogonal Function (EOF) or Rotated Empirical Orthogonal Function (REOF). These facts are illustrated with an example of winter wind speed regionalization in the Iberian Peninsula through the period (1979 − 2014). This study also reveals that the North Atlantic Oscillation (NAO) has a high influence over the wind distribution in the Iberian Peninsula in a subset of years in the considered period. [ABSTRACT FROM AUTHOR]

Regional models used for downscaling the European climate usually include a relatively small area of the Atlantic Ocean and are uncoupled, with the SST used as lower boundary conditions much coarser than the mesh of the regional atmospheric model. Concerns thus arise about the proper representation of the oceanic influence and the role of air-sea coupling in such experiments. A complex orography and the exposure to different air and ocean masses make the Iberian Peninsula (IP) an ideal test case for exploring the impact of including explicitly the North Atlantic in the regional domain and the added value that coupling brings to regional climate modeling. To this end, the regionally-coupled model ROM and its atmospheric component, the regional atmospheric model REMO are used in a set of coupled and uncoupled experiments forced by the ERA-Interim reanalysis and by the global climate model MPI-ESM. The atmospheric domain is the same in all simulations and includes the North Atlantic and the ocean component is global and eddy permitting. Results show that the impact of air-sea coupling on the IP winter biases can be traced back to the features of the simulated North Atlantic Ocean circulation. In summer, it is the air-sea interactions in the Mediterranean that exert the largest influence on the regional biases. Despite improvements introduced by the eddy-permitting ocean, it is suggested that a higher resolution could be needed for a correct simulation of the features of the large-scale atmospheric circulation that impact the climate of the IP. [ABSTRACT FROM AUTHOR]

Migratory birds spend periods of the year in different locations as a response to seasonal changes in environmental suitability. They are classified as either 'niche‐trackers' or 'niche‐switchers', depending on whether they track or switch environmental conditions throughout the year. However, the relationship between these strategies and their migratory behaviour is still unclear. Here we examine whether migratory European Robins Erithacus rubecula and Eurasian Blackcaps Sylvia atricapilla track environmental conditions between breeding and wintering areas and whether their behaviour differs from that of their sedentary counterparts. We used ringing data for both migratory and sedentary individuals wintering sympatrically in the Iberian Peninsula to assess the environmental conditions relating to their seasonal distributions. We explored seasonal niche‐tracking using two multivariate analyses with alternative sets of predictor variables (landscape and climate) to generate different environmental scenarios. Our results show that migratory individuals track similar climatic conditions throughout their seasonal distributions, whereas sedentary birds cope with great variation in climate over the course of the year. In addition, migratory birds show less seasonal overlap in the landscape structure of their chosen habitats compared with sedentary individuals. These results suggest that there is a trade‐off between, on the one hand, the cost for migrants of travelling long distances and, on the other, the increased flexibility required by sedentary birds if they are to tolerate a wider suite of environmental conditions within their permanent ranges. Given that sedentary populations in the southern Iberian Peninsula seem to be linked to populations of migratory individuals of these two species that started to move northwards after the last glacial cycle, the observed patterns suggest that migrant birds represent a fraction of the southern population that is specialized in the exploitation of a narrower range of environmental conditions. [ABSTRACT FROM AUTHOR]

As the global climate warms, increased aridity is expected to become a major determinant of forest productivity and tree growth. In gymnosperms, wood density quantified at seasonal to annual scales can be related to changes in tracheid lumen size due to alterations in soil water availability. In this way, minimum wood density (MND) has been shown to respond negatively to early growing-season precipitation in several conifers because dry conditions reduce tracheid lumen size and consequently increase MND. We investigated if this relationship between spring precipitation and MND applies to four conifer species (Abies alba , Pinus sylvestris , Pinus nigra , Juniperus thurifera) in NE Spain from mesic (A. alba , P. sylvestris) to xeric (P. nigra , J. thurifera) conditions. We further assessed how climate, precipitation, and drought-affected tree-ring width (TRW) and MND at several time scales to test if water shortage in spring increases MND and decreases TRW over time and seasonally. Lastly, we quantified the post-drought MND recovery. We found the strongest negative correlations between MND and spring precipitation in P. nigra followed by J. thurifera. In these two species, the associations between MND and 9-month long droughts peaked in early spring (P. nigra , r = − 0.73 ; J. thurifera , r = − 0.50). Juniperus thurifera presented a better post-drought recovery (decrease in MND), followed by P. nigra and P. sylvestris. We conclude that MND is a reliable and accurate proxy of drought severity during spring in conifers subjected to seasonal water shortage. MND can be used as an early-warning indicator of short- and long-term changes in the responses of trees to water shortage. [ABSTRACT FROM AUTHOR]

1. Climate change is expected to produce shifts in species distributions as well as behavioural, life‐history, and/or morphological adaptations to find suitable conditions or cope with the altered environment. Most of our knowledge on this issue comes from studies on vertebrates, mainly endotherm species. However, it remains uncertain how small ectotherms, such as insects, respond to increased temperature. 2. This study tested whether climate change over the last 100 years (1904–2013) has affected morphological and functional traits in workers of the social wasp Dolichovespula sylvestris in the Iberian Peninsula. 3. Head width and forewing length, as well as body mass and wing area (assuming no change in shape), decreased over time and with increased mean annual temperature, even when controlling for geographical location and altitude. Interestingly, wing size decreased with a steeper slope compared with body size. If there is no change in wing shape, this would lead to an invariable wing loading (body mass:wing area ratio) over time, with potential consequences on flying ability of more recent (and thus smaller) wasp individuals. 4. These results suggest that recent climate change is leaving morphological signatures in social wasps, increasing the evidence for this phenomenon in insects. The data furthermore suggest that the known efficient thermoregulatory ability of social insect colonies may not successfully buffer the effect of global warming. [ABSTRACT FROM AUTHOR]

New 10Be dates for glacial landforms in the Fuentes Carrionas area (Cantabrian Mountains, nothern Spain) are presented. Mapped and dated landforms in Fuentes Carrionas made possible a palaeoglacier reconstruction for four glacial stages. Results were compared to other nearby palaeoenvironmental proxies, so a final approximation on the mean annual temperature and annual precipitation that caused the four glacial advance stages is proposed. Glaciers reached their maximum extension at 36 ka, in a cold and dry environment. A second advance stage took place between 18.5 and 19.5 ka, during the Last Glacial Maximum (LGM), when glaciers advanced in a wet environment, with positive rainfall anomalies. A third glacial advance was dated during the Oldest Dryas, in which climate shifted to extremely cold and dry conditions. Finally, a last stage has been identified and proposed to the Younger Dryas, in which precipitation anomalies are negligible. Our results confirm some of the previously made palaeoglacial and palaeoenvironmental inferences for the Iberian Peninsula, as well as provide valuable and accurate anomalies, which are useful for climate modelling. [ABSTRACT FROM AUTHOR]

To assess the regional multi-decadal to multi-centennial climate variability along the southern Iberian Peninsula during the mid- to late-Holocene record of paleo-environmental indicators from marine sediments were established for two sites in the Alboran Sea (ODP-161-976A) and the Gulf of Cádiz (GeoB5901-2). High-resolution records of organic geochemical properties and planktic foraminiferal assemblages are used to decipher precipitation and vegetation changes as well as hydrological conditions with respect to sea surface temperature (SST) and marine primary productivity (MPP). As a proxy for precipitation change, records of plant-derived n -alkane composition suggest a series of five distinct dry episodes in southern Iberia at 5.4±0.3 ka cal BP, from 5.1 to 4.9±0.1 ka cal BP, from 4.8 to 4.7±0.1 ka cal BP, from 4.4 to 4.3±0.1 ka cal BP, and at 3.7±0.1 ka cal BP. During each dry episode the vegetation suffered from reduced water availability. Interestingly, the dry phase from 4.4 to 4.3±0.1 ka cal BP is followed by a rapid shift towards wetter conditions revealing a more complex pattern in terms of its timing and duration than was described for the 4.2 ka event in other regions. The series of dry episodes as well as closely connected hydrological variability in the Alboran Sea were probably driven by NAO-like (North Atlantic Oscillation) variability. In contrast, surface waters in the Gulf of Cádiz appear to have responded more directly to North Atlantic cooling associated with Bond events. In particular, during Bond events 3 and 4, a pronounced increase in seasonality with summer warming and winter cooling is found. [ABSTRACT FROM AUTHOR]

An automated atmospheric rivers (ARs) detection algorithm is used for the North Atlantic Ocean basin that allows the identification and a comprehensive characterization of the major AR events that affected the Iberian Peninsula over the 1948-2012 period. The extreme precipitation days in the Iberian Peninsula and their association (or not) with the occurrence of ARs is analyzed in detail. The extreme precipitation days are ranked by their magnitude and are obtained after considering 1) the area affected and 2) the precipitation intensity. Different rankings are presented for the entire Iberian Peninsula, for Portugal, and for the six largest Iberian river basins (Minho, Duero, Tagus, Guadiana, Guadalquivir, and Ebro) covering the 1950-2008 period. Results show that the association between ARs and extreme precipitation days in the western domains (Portugal, Minho, Tagus, and Duero) is noteworthy, while for the eastern and southern basins (Ebro, Guadiana, and Guadalquivir) the impact of ARs is reduced. In addition, the contribution from ARs toward the extreme precipitation ranking list is not homogenous, playing an overwhelming role for the most extreme precipitation days but decreasing significantly with the less extreme precipitation days. Moreover, and given the narrow nature of the ARs, the location of the ARs over each subdomain is closely related to the occurrence (or not) of extreme precipitation days. [ABSTRACT FROM AUTHOR]

A method for ranking daily precipitation events is presented based on the most comprehensive database of daily gridded precipitation dataset available for the Iberian Peninsula spanning from 1950 to 2008. The magnitude of an event is obtained after considering the area affected as well as its intensity in every grid point and taking into account the daily normalized departure from climatology. Different precipitation rankings are presented considering the entire Iberian Peninsula, Portugal and also the six largest river basins in the Iberian Peninsula. [ABSTRACT FROM AUTHOR]

Understanding functional diversity is critical to manage and preserve biodiversity and ecosystem functioning in the face of global change. However, the efforts to characterize this functional component have been mostly directed to vascular vegetation. We sampled lichen-dominated biological soil crusts (BSCs) in semiarid grasslands along an environmental gradient in the Iberian Peninsula. We characterized five effect functional traits for 31 lichens species, and evaluated the influence of large scale (i.e. precipitation) and small scale factors (i.e. substrate type, shrub presence, Stipa tenacissima presence) on dominant trait values; i.e. community weighted means, and functional divergence; i.e. Rao quadratic entropy in 580 sampling quadrats. Across the gradient, we found multiple trait shifts and a general increase of functional divergence with increasing precipitation. We also observed that substrate type and small scale biotic factors determined shifts in all traits studied, while these factors affected less to functional divergence. Comparing functional diversity with taxonomic diversity, we found contrasting responses to both large and small scale factors. These findings suggest that BSC community trait composition is influenced by multi-scale abiotic and biotic factors with environmental filtering dominating at large spatial scales and limiting similarity at specific small scales. Also, our results emphasize the potential differences between taxonomic and functional diversity in response to environmental factors. We concluded that functional diversity of BSCs not only provides novel and critical knowledge of BSC community structure, but also it should be considered as a critical tool in biodiversity conservation strategies, ecosystem services assessment and ecological modelling. [ABSTRACT FROM AUTHOR]

ABSTRACT Heinrich Event 3 (H3) is well documented in the North Atlantic Ocean as a cooling event that occurred ca. 31 000 years ago. Deep-sea cores around the Iberian Peninsula coastline have been analysed to characterize the H3 event, but there are no data on the terrestrial response to this event. Here we present for the first time an analysis of terrestrial proxies for characterizing the H3 event, using the small-vertebrate assemblage (comprising small mammals, squamates and amphibians) from the Galls Carboners cave, an archaeo-palaeontological deposit located in the Prades mountain range in the north-eastern Iberian Peninsula. This assemblage shows the H3 event to be characterized in north-eastern Iberia by harsher and drier terrestrial conditions than today. Our results were compared with the small-vertebrate assemblage data recovered from present-day Strix aluco pellets available from this site, as well as with the general H3 event fluctuations and with other sites where the previous Heinrich events (H5 and H4) and subsequent Late Glacial Maximum have been detected in the Mediterranean and Atlantic regions of the Iberian Peninsula. Terrestrial proxies seem to follow the same climatic pattern as detected in the deep-sea cores at NorthGRIP and the Iberian margins. [ABSTRACT FROM AUTHOR]

Variability in precipitation affects annual total records and causes instability in rainfall distribution throughout the year. Our aim in this study was to develop a procedure, based on pluviometric centralisation and dispersion parameters, that is able to characterise rainfall distribution throughout a year of precipitation in a unique, condensed and precise manner. This enabled the evolution of intra-annual precipitation from 1837 to 2010 in the southwest of the Iberian Peninsula to be determined. The obtained results showed irregular oscillations of the parameters during the selected period. Specifically, patterns of precipitation in recent decades revealed the following differentiating features: the displacement of the most intense rainy periods in autumn with a consequent decrease in precipitation in spring, and more erratic distribution throughout the year with an increase of the frequency of intra-annual dispersion peaks. [ABSTRACT FROM AUTHOR]

This study illustrates the sensitivity of regional climate change projections to the model physics. A single-model (MM5) multi-physics ensemble of regional climate simulations over the Iberian Peninsula for present (1970-1999) and future (2070-2099 under the A2 scenario) periods is assessed. The ensemble comprises eight members resulting from the combination of two options of parameterization schemes for the planetary boundary layer, cumulus and microphysics. All the considered combinations were previously evaluated by comparing hindcasted simulations to observations, none of them providing clearly outlying climates. Thus, the differences among the various ensemble members (spread) in the future projections could be considered as a matter of uncertainty in the change signals (as similarly assumed in multi-model studies). The results highlight the great dependence of the spread on the synoptic conditions driving the regional model. In particular, the spread generally amplifies under the future scenario leading to a large spread accompanying the mean change signals, as large as the magnitude of the mean projected changes and analogous to the spread obtained in multi-model ensembles. Moreover, the sign of the projected change varies depending on the choice of the model physics in many cases. This, together with the fact that the key mechanisms identified for the simulation of the climatology of a given period (either present or future) and those introducing the largest spread in the projected changes differ significantly, make further claims for efforts to better understand and model the parameterized subgrid processes. [ABSTRACT FROM AUTHOR]

This work assesses the influence of the model physics in present-day regional climate simulations. It is based on a multi-phyiscs ensemble of 30-year long MM5 hindcasted simulations performed over a complex and climatically heterogeneous domain as the Iberian Peninsula. The ensemble consists of eight members that results from combining different parametrization schemes for modeling the Planetary Boundary Layer, the cumulus and the microphysics processes. The analysis is made at the seasonal time scale and focuses on mean values and interannual variability of temperature and precipitation. The objectives are (1) to evaluate and characterize differences among the simulations attributable to changes in the physical options of the regional model, and (2) to identify the most suitable parametrization schemes and understand the underlying mechanisms causing that some schemes perform better than others. The results confirm the paramount importance of the model physics, showing that the spread among the various simulations is of comparable magnitude to the spread obtained in similar multi-model ensembles. This suggests that most of the spread obtained in multi-model ensembles could be attributable to the different physical configurations employed in the various models. Second, we obtain that no single ensemble member outperforms the others in every situation. Nevertheless, some particular schemes display a better performance. On the one hand, the non-local MRF PBL scheme reduces the cold bias of the simulations throughout the year compared to the local Eta model. The reason is that the former simulates deeper mixing layers. On the other hand, the Grell parametrization scheme for cumulus produces smaller amount of precipitation in the summer season compared to the more complex Kain-Fritsch scheme by reducing the overestimation in the simulated frequency of the convective precipitation events. Consequently, the interannual variability of precipitation (temperature) diminishes (increases), which implies a better agreement with the observations in both cases. Although these features improve in general the accuracy of the simulations, controversial nuances are also highlighted. [ABSTRACT FROM AUTHOR]

Crops growing in the Iberian Peninsula may be subjected to damagingly high temperatures during the sensitive development periods of flowering and grain filling. Such episodes are considered important hazards and farmers may take insurance to offset their impact. Increases in value and frequency of maximum temperature have been observed in the Iberian Peninsula during the 20th century, and studies on climate change indicate the possibility of further increase by the end of the 21st century. Here, impacts of current and future high temperatures on cereal cropping systems of the Iberian Peninsula are evaluated, focusing on vulnerable development periods of winter and summer crops. Climate change scenarios obtained from an ensemble of ten Regional Climate Models (multimodel ensemble) combined with crop simulation models were used for this purpose and related uncertainty was estimated. Results reveal that higher extremes of maximum temperature represent a threat to summer-grown but not to winter-grown crops in the Iberian Peninsula. The study highlights the different vulnerability of crops in the two growing seasons and the need to account for changes in extreme temperatures in developing adaptations in cereal cropping systems. Finally, this work contributes to clarifying the causes of high-uncertainty impact projections from previous studies. [ABSTRACT FROM AUTHOR]

Hindcasts with reanalysis-driven regional climate models (RCMs) are a common tool to assess weather statistics (i.e. climate) and recent changes and trends. A remote sensing-based method to investigate the added value of surface marine RCM wind speed is introduced. The capability of the dynamical downscaling approach (with spectral nudging applied) to add value to the reanalysis wind speed forcing is assessed by the comparison with QuikSCAT Level 2B 12.5 km (L2B12) swath data in European waters for 2000-2007. Co-location criteria are within 0.1° and 0.06° in longitudinal and latitudinal distance from RCM grid points and within 10 min. In the wind speed range, QuikSCAT L2B12 is reliably reproducing (3-20 m s), dynamically downscaled wind speed does not show an added value in 'open ocean' areas. However, in coastal areas with complex topography, the regional models show an added value, especially around Iceland and the Iberian Peninsula and in the Mediterranean, Baltic and Irish Seas, validating the findings of previous in situ data-based studies on the added value. Strong interseasonal differences exist, in winter enhanced cyclonic and meso-cyclonic activity increases the potential of dynamical downscaling. In winter time, the added value is more pronounced around Iceland and Greenland, south of Iceland and within the Gulf of Lyon/Mistral region. Summarizing the presented method can be easily applied for other ocean areas, making QuikSCAT a valuable tool to identify marine regions where dynamical downscaling adds value to surface marine wind speed. A detailed comparison of 10 m winds from the National Centres of Environmental Prediction (NCEP)/National Centre for Atmospheric Research (NCAR) and the newer NCEP/DOE-II reanalyses is presented in the annex, motivating the use of the NCEP/NCAR reanalysis in the added value assessment. Copyright © 2010 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

1. The importance of dispersal capacity in structuring beta-diversity gradients has been pointed out in a number of recent studies, making geographical distance (GD) an important predictor of the composition of assemblages apart from environment. In this study, we analyse the relative importance of climate, habitat complexity and GD in four spider families with different dispersal tendencies in the centre of the Iberian Peninsula. 2. Regional beta-diversity was calculated for the four families and values were bootstrapped to test for significant difference between groups. Mantel tests assessed the explanatory capacity of four potential predictors – climatic similarity, similarity of vegetation complexity, GD and cost distance (CD) considering topography – on faunistic similarity. Simple regressions were used to compare decay rates, and bootstrapping tested for significant differences in coefficients. 3. Regional beta-diversity values were higher in less vagile families. Climatic distance was strongly correlated with faunistic dissimilarity in the four families, whereas GD had no explanatory power. Except in one family, CD was correlated with faunistic dissimilarity but its independent association was negligible when controlling for climate. 4. Both the pattern of regional beta-diversity among families and the pattern of variation in species composition explained by climate are consistent with the hypothesis that dispersion capacity influences the composition of the assemblages. However, climate distance was the main factor determining species sorting in space while GD had a weak effect. Differences in the degree of specialisation or nonlinear relationships between species composition and space may obscure the signal of GD at the scale of work. [ABSTRACT FROM AUTHOR]

A climatic description of total cloudiness in the Iberian Peninsula is presented, based on three global gridded datasets: the International Satellite Cloud Climatology Project (ISCCP) D2 data, gridded data (TS 2.1) from the Climate Research Unit (CRU), and the ECMWF Re-Analyses data (ERA-40). While the first grid data product is based on satellite imagery, the second series is from observations from the surface, and the third uses several types of observations that are assimilated into a grid. Since the series differ in their extension, the study has been limited to the shared period of 1984–2002 in regards to comparing results from the three sources of data. These results indicate that, in the Iberian Peninsula, the mean annual cloudiness ranges from 35–65% of fractional sky cover, depending on location and on data source. Seasonal evolution shows a very clear minimum of cloudiness that appears in summer and a maximum in winter. Important differences appear among the three sources; these differences are variable both in space and during the year. Regarding decadal trends of cloudiness, the results are sometimes contradictory: on an annual basis, ISCCP and ERA indicate general decreasing cloudiness, while CRU data show a continuous positive trend. [ABSTRACT FROM AUTHOR]

We model the past and future distribution of Pinus sylvestris in the Iberian Peninsula using the random forest algorithm, a machine learning technique that implements an automatic combination of tree predictors. In order to model the past, we chose two of the most climatically significant events recognized affecting the species distribution: the last glacial maximum (LGM, 21 000 cal. BP), and the mid Holocene (6000 cal. BP). In order to model the distributions, we based the future scenarios of climate change upon the four storylines projected by the Intergovernmental Panel on Climate Change (A1, A2, B1 and B2). The results obtained for the past show a contraction in the distribution area during the LGM and a subsequent expansion, coinciding with an improvement in climate in the mid Holocene. The presence of isolated populations of Pinus sylvestris at low altitudes could support the existence of refuges for Northern European taxa. The results obtained for the future, even in the least aggressive scenario, show a rapid decrease in this species' distribution and a vertical migration as a response to climate change. Pinus sylvestris populations would be restricted in the future to the higher altitudes of the mountains in the north of the Iberian Peninsula (mainly the Pyrenees), and the species would disappear from the central and southern mountain ranges. These results identify a risk to high-mountain forest species in the Iberian Peninsula from the effects of global warming. [ABSTRACT FROM AUTHOR]

'Little Ice Age' (LIA) glacier advance has been registered in three of the main Iberian high mountain areas: Pyrenees, Picos de Europa and Sierra Nevada. During the LIA, three different glacial environments have been differentiated in these three ranges. A high mountain glacial environment exists in the Pyrenees, where the altitude and northern latitude developed the most complex glacial environment between the oceanic influence on the western side and the Mediterranean influence on the eastern side. In the Pyrenees the LIA glaciation occurred in 15 massifs where there are up to 100 cirques; however, today the glaciers remain only in the highest peaks. A marginal glacial environment exists in the Picos de Europa related to the oceanic influence and topography in an Atlantic high mountain: there were six glaciers in the Picos de Europa Massif during the LIA. A marginal glacial environment also exists in the Sierra Nevada, related to the northern orientation and altitude in a Mediterranean high mountain, where only one glacier, the southernmost of Europe, occurred during the LIA. Several variations of LIA glaciers have been found: historical maximum (from the end of the seventeenth to the beginning of the eighteenth centuries); minor retreat with secondary regrowth (mid-eighteenth to nineteenth centuries); and continuous retreat (from the end of the nineteenth to the beginning of the twentieth centuries); followed by the almost complete extinction of the glaciers and an increase in the periglacial environment. There are now 29 glaciers in the Pyrenees, four buried icepatches in the Picos de Europa and one buried icepatch in the Sierra Nevada. The rise of ELAs from the last LIA glacial maximum until the present allows the calculation of an increase in temperatures of around 0.9°C in the Iberian high mountains. [ABSTRACT FROM AUTHOR]

Daily pluviometric records of 43 meteorological stations across the Iberian Peninsula have permitted a detailed analysis of dry spell patterns for the period 1951–2000 by distinguishing daily amount thresholds of 0.1, 1.0, 5.0 and 10.0 mm/day. The analyses are based on three annual series, namely the number of dry spells, N, the average dry spell length, L, and the extreme dry spell length, L max. First, the statistical significance of local trends for the annual series of N, L and L max has been investigated by means of the Mann-Kendall test and significant field trends have been established by means of Monte Carlo simulations. Clear signs of negative field trends are detected for N (1.0 and 10.0 mm/day) and L (0.1 mm/day). Second, the Weibull model fits well the empirical distributions of dry spell lengths for all the rain gauges, whatever the daily amount threshold, with a well ranged spatial distribution of their parameters u and k. On the basis of the Weibull distribution, return period maps for 2, 5, 10, 25 and 50 years have been obtained for dry spell lengths with respect to the four daily threshold levels. While for 0.1 and 1.0 mm/day the longest dry spells are expected at the south of the Iberian Peninsula, for 5.0 and 10.0 mm/day they are mostly detected at the southeast. Finally, the elapsed time between consecutive dry spells has been analysed by considering the same rain amount thresholds and different dry spell lengths at increasing intervals of 10 days. This analysis makes evident a significant negative field trend of the elapsed time between consecutive dry spells of lengths ranging from 10 to 20 days for daily amount thresholds of 1.0, 5.0 and 10.0 mm/day. [ABSTRACT FROM AUTHOR]

Atmospheric rivers are important atmospheric features implicated in the global water vapor budget, the cloud distribution, and the associated precipitation. The ARiD (Atmospheric River Detector) code has been developed to automatically detect atmospheric rivers from water vapor flux and has been applied to the ECMWF ERA5 archive over the period 1980–2020 above the Atlantic Ocean and Europe. A case study of an atmospheric river formed in the East Atlantic on August 2014 that reached France has been detailed using ECMWF ERA5 reanalysis, ground based observation data, and satellite products such as DARDAR, AIRS, GPCP, and GOES. This atmospheric river event presents a strong interaction with an intense upper tropospheric jet stream, which induced stratosphere–troposphere exchanges by tropopause fold. A 1980–2020 climatology of atmospheric rivers over Europe has been presented. The west of France, Iberian Peninsula, and British Islands are the most impacted regions by atmospheric rivers with an occurrence of up to four days per month during the October–April period. Up to 40% of the precipitation observed on the west European coast can be linked to the presence of ARs. No significant trend in the occurrence of the phenomena was found over 1980–2020. [ABSTRACT FROM AUTHOR]

Due to climate change, the Iberian Peninsula is suffering an increasing trend of extreme temperature events. The main objective of this study is to analyse this trends in frequency, duration and intensity of warm events and heat waves. The datasets used are 14 different regionalized dynamic climate projections. We choose the projections that present a spatial dependence similar to that of observed data. The spatial dependence is calculated by adjusting the data to max-stable processes. The observed data belong to the SPAIN02 grid for the period 1961–2000. We apply the Mann-Kendall test and the Theil-Sen estimator to calculate model trends in the future period (2011–2099). We have studied future extreme temperature events using two different definitions. One varying the threshold for each period and the other keeping it constant. The results show that the variability of maximum temperatures is decreasing for the western region of the Peninsula, while the Mediterranean area will see an increase in this variability. There will be an increase in the frequency of warm events for the southwestern corner of the Peninsula. Also, maximum temperatures will be higher in this area at the end of the century. However, in the Mediterranean region the warm events will last longer. Heat waves will be more frequent throughout the territory and more lasting in the Mediterranean area. We also found that studying extreme events using a varying threshold allows these events to be studied from the point of view of the variability of maximum temperatures, while if the study is carried out maintaining the threshold constant the results will be more direct. [ABSTRACT FROM AUTHOR]