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© 2006 American Meteorological Society. The authors thank the ECMWF for providing their reanalysis data. We also thank the Instituto Nacional de Meteorología (INM) for providing the precipitation data for the Spanish stations. We thank the European Climate Assessment (ECA) project (supported by the Network of European Meteorological Services EUMETNET). This work was supported by the Portuguese Science Foundation (FCT) through project VAST (Variability of Atlantic Storms and Their impact on land climate) Contract POCTI/ CTA/46573/2002, cofinanced by the European Union under program FEDER. The Universidad Autónoma de Madrid (UAM) also supported this work. Thanks to Julio Díaz for his help. Finally, the suggestions of two anonymous reviewers helped to improve the original manuscript., March monthly accumulated precipitation in the central and western regions of the Iberian Peninsula presents a clear continuous decline of 50% during the 1960-97 period. A finer analysis using daily data reveals that this trend is exactly confined to the month of March. However, this is merely the most visible aspect of a larger phenomenon over the North Atlantic/European sector. The European precipitation trends in March for the period 1960-2000 show a clear distribution of increasing precipitation in the northern regions (the British Isles and parts of Scandinavia) together with decreasing trends throughout the western Mediterranean Basin. Relevant circulation changes over the North Atlantic and European sectors explain these precipitation trends. First, a regional Eulerian approach by means of a weather-type (WT) classification shows that the major rainfall contributors in March display significantly decreasing frequencies for the Iberian Peninsula, in contrast to the corresponding "wet" weather types for the U.K./Ireland sector, which display increasing frequencies. Within a larger context, a Lagrangian approach, based oil the analysis of storm tracks over Europe and the North Atlantic region, reveals dramatic changes in the location of cyclones in the last four decades that coincide with the corresponding precipitation trends in Europe. The North Atlantic Oscillation is suggested to be the most important large-scale factor controlling both the circulation changes and the precipitation trends over the Euro-Atlantic area in March. Finally, the potential impact of reduced precipitation for rivers and water resources in the Iberian Peninsula is considered., Network of European Meteorological Services EUMETNET, Fundação para a Ciência e a Tecnologia (FCT), Portugal, Program FEDER (UE), Unión Europea (UE), Project VAST (Variability of Atlantic Storms and Their impact on land climate). UE, Universidad Autónoma de Madrid (UAM), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

This study was supported by the EU/FP6 project CIRCE (#036961) (D. B., J.L., R. T., and R. G.), the Instituto Dom Luiz-Faculdade de Ciencias da Universidade de Lisboa project ENAC (PTDC/AAC-CLI/103567/2008) (D. B., R. T.), the Swiss National Science Foundation (Swiss National Center of Competence in Research-Climate) (E. F.), the EU/FP7 project ACQWA (#212250) (J.L.), the Deutsche Forschungsgemeinschaft project PRIME (LU1608/1-1, AOBJ: 568460) within the Priority Program 'INTERDYNAMIK' (J.L.), the project "Historical climatology of the Middle East based on Arabic sources back to ad 800" (LU 1608/2-1 AOBJ 575150) (J.L.) and the project "Climate Change and Extreme Weather in Hesse-Analysis of observation data and ensemble projections for the 21st century" funded by the Hessian Centre on Climate Change and Geology (J.L.). The ENSEMBLES data used in this work was funded by the European Union/FP6 project ENSEMBLES (#505539), whose support is gratefully acknowledged. 20th Century and National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalyses data were provided by the National Oceanic and Atmospheric Administration (NOAA)/Office of Oceanic and Atmospheric Research (OAR)/Earth System Research Laboratory (ESRL) Physical Sciences Division, Boulder, Colorado, USA, from their Web site at www.esrl.noaa.gov/psd/., The summer of 2010 was exceptionally warm in eastern Europe and large parts of Russia. We provide evidence that the anomalous 2010 warmth that caused adverse impacts exceeded the amplitude and spatial extent of the previous hottest summer of 2003. "Mega-heatwaves" such as the 2003 and 2010 events likely broke the 500-year-long seasonal temperature records over approximately 50% of Europe. According to regional multi-model experiments, the probability of a summer experiencing mega-heatwaves will increase by a factor of 5 to 10 within the next 40 years. However, the magnitude of the 2010 event was so extreme that despite this increase, the likelihood of an analog over the same region remains fairly low until the second half of the 21st century., EU, Instituto Dom Luiz-Faculdade de Ciencias da Universidade de Lisboa, Swiss National Science Foundation (Swiss National Center of Competence in Research-Climate), Deutsche Forschungsgemeinschaft, Hessian Centre on Climate Change and Geology, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Springer 2005., Meteorological observations made on board ships prior to 1854 have until now been overlooked in climatological research largely as a result of the lack of rigorous abstraction and treatment criteria. However, the CLIWOC project has shown that millions of potentially valuable observations have been preserved throughout Europe in the many logbooks that were prepared by officers in the navies of the great powers. Moreover these data can be used and treated in a fashion similar to today's ship-based instrumental observations. The most significant logbook collections are from Spain, the UK, the Netherlands and France. This paper describes the main archives where the logbooks can be found and provides an account of their contents and of the manner in which they were set out. The potential of this source is emphasised by the fact that whilst the CLIWOC project abstracted data for 300,000 days, nearly 90% of the European logbook collections have yet to be examined. This paper concludes with a discussion as to the direction of future studies in this important field., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 StudiaGeo s.r.o., Two different groups of indices have been defined to analyze the evolution of global temperature between 1958 and 1998. All the indices were evaluated at three different levels (850, 500 and 200 hPa), and averaged indices were calculated using the whole globe, continental areas and oceanic areas. The first group of indices analyzes the area of the world covered with higher and lower than normal temperatures, detecting a slight cooling in the 200 hPa level. The second group of indices studies the annual frequency of extreme events, and again, it is at 200 hPa where the most intense variation is detected. Finally, an analysis is performed to determine the regions most sensible to variations in the occurrence of extreme events. Tropical areas are mostly responsible of the variations detected in the second group of indices., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

©2003 American Meteorological Society., Spanish historical archives contain a vast store of information about Spain and its former colonies in America and Asia. Some searches for climate-related information within these archives have been undertaken recently, but they have been by no means exhaustive. This paper discusses the principal archives and shows, by means of several examples, that they exhibit a high potential for inferring past climate over a wide range of timescales and geographical areas. Extraction of such information is often time consuming, and requires a combination of archival, historical, and climatological expertise, and the development of individualized methodologies to fit each situation and type of data. In spite of these difficulties, the archives can be particularly useful in many cases where there are no alternative sources of climate data. Thus, the complexities of the multidisciplinary effort required should not discourage other researchers from undertaking similar studies., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© EGS - Springer-Verlag 2000. Topical Editor F. Vial thanks F. Lott for his help in evaluating this paper., The North Atlantic Oscillation (NAO) and the Southern Oscillation (SO) are compared from the standpoint of a possible common temporal scale of oscillation. To do this a cross-spectrum of the temporal series of NAO and SO indices was determined, finding a significant common oscillation of 6-8 years. To assure this finding, both series were decomposed in their main oscillations using singular spectrum analysis (SSA). Resulting reconstructed series of 6-8 years' oscillation were then cross-correlated without and with pre-whitened, the latter being significant. The main conclusion is a possible relationship between a common oscillation of 6-8 years that represents about 20% of the SO variance and about 25% of the NAO variance., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Springer 2005. This work was supported by the European Commission, DG XII, Programme 2.4.1: ‘Better exploitation of existing data and adaptation of existing systems’, EC Framework V Project EVK2-CT-2000-00090 (CLIWOC). The authors thank David Parker for his many suggestions during the preparation of this paper. Scott Woodruff is thanked for providing the US Maury data of Figure 5. The CLIWOC database is accessible via Internet via http://www.ucm.es/info/cliwoc/, from which links are included to allow for consultation of the imaged logbooks., We have compiled a meteorological database over the world's oceans by digitizing data from European ship logbooks of voyages in the period 1750-1854. The observations are carefully reviewed and transformed into quantitative data. The chief contents of the database are wind direction and wind force information, from a period without standardized scales. It is found that the information content of these so-called non-instrumental data is much higher than previously believed. The 105-year CLIWOC database extends existing meteorological world ocean databases like ICOADS back in time by a full century., European Commission, Directorate General XII (DG XII), Unión Europea (UE), 5th Framework Project FP% (UE), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 by the American Geophysical Union. The authors would like to thank two anonymous reviewers for their valuable comments. The Spanish Science and Technology Department supported this study trough the VALIMOD (Climatic VALIdation of Conceptual MODels) project (REN2002-04558-C04-01)., This paper examines the role of North Hemisphere snow cover in the linkage between the winter North Atlantic Oscillation (NAO) and the summer Northern Annular Mode (NAM). This transition is partially supported by the persistence of the NAO-induced snow cover anomalies and the asymmetric thermal distribution induced by summer snow cover. We define an index of subpolar temperature difference which links winter NAO with the subsequent summer NAM. The index is also significant in the linkage between summer and winter climates and can be used as an useful predictor of the upcoming winter NAO., Spanish Science and Technology Department, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© European Geophysical Society 2002. Topical Editor J.-P. Duvel thanks I. Durre and J. Coiffier for their help in evaluating this paper., Extremely hot days (EHD) in Madrid have been analysed to determine the synoptic patterns that produce EHDs during the period of 1955-1998. An EHD is defined as a day with maximum temperature higher than 36.5°C, a value which is the threshold for the intense effects on mortatility and it coincides with the 95 percentile of the series. Two different situations have been detected as being responsible for an EHD occurrence, one more dynamical, produced by southern fluxes, and another associated with a stagnation situation over Iberia of a longer duration. Both account for 92% of the total number of days, thus providing an efficient classification framework. A circulation index has been derived to characterise and forecast an EHD occurrence. This paper shows that EHD occur in Madrid during short duration events, and no long heat waves, like those recorded in other cities, are present. Additionally, no clear pattern can be detected in the EHD frequency; the occurrence is tied to changes in the summer location of the Azores high., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 by the American Geophysical Union., The quasi-biennial oscillation (QBO) signal in stratospheric zonal and meridional wind, temperature, and geopotential height fields is analyzed based on the use of the National Centers for Environmental Prediction (NCEP) reanalysis (1958-2001). The multitaper method-singular value decomposition (MTM-SVD), a multivariate frequency domain analysis method, is used to detect significant and spatially coherent narrowband oscillations. The QBO is found as the most intense signal in the stratospheric zonal wind. Then, the MTM-SVD method is used to determine the patterns induced by the QBO at every stratospheric level and data field. The secondary meridional circulation associated with the QBO is identified in the obtained patterns. This circulation can be characterized by negative (positive) temperature anomalies associated with adiabatic rising (sinking) motions over zones of easterly (westerly) wind shear and over the subtropics and midlatitudes, while meridional convergence and divergence levels are found separated by a level of maximum zonal wind shear. These vertical and meridional motions form quasi-symmetric circulation cells over both hemispheres, though less intense in the Southern Hemisphere., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Author(s) 2005. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License. The authors wish to thank M. Salmon, D. Efthymiadis and M. Salas from the Climatic Research Unit for their help during the first phases of the work. This work was supported by the EC Framework V Project EVK2-CT-2000-00090 (CLIWOC)., Measurements of wind strength and direction abstracted from European ships' logbooks during the recently finished CLIWOC project have been used to produce the first gridded Sea Level Pressure ( SLP) reconstruction for the 1750 - 1850 period over the North Atlantic based solely on marine data. The reconstruction is based on a spatial regression analysis calibrated by using data taken from the ICOADS database. An objective methodology has been developed to select the optimal calibration period and spatial domain of the reconstruction by testing several thousands of possible models. The finally selected area, limited by the performance of the regression equations and by the availability of data, covers the region between 28° N and 52° N close to the European coast and between 28° N and 44° N in the open Ocean. The results provide a direct measure of the strength and extension of the Azores High during the 101 years of the study period. The comparison with the recent land-based SLP reconstruction by Luterbacher et al. ( 2002) indicates the presence of a common signal. The interannual variability of the CLIWOC reconstructions is rather high due to the current scarcity of abstracted wind data in the areas with best response in the regression. Guidelines are proposed to optimize the efficiency of future abstraction work., Fifth Framework Programme (FP5), UE, Unión Europea (EU), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Author(s) 2008. © Copernicus Gesellschaft MBH 2008. This work is licensed under a Creative Commons License., One of the main problems in climate reconstruction from documentary sources is the evaluation of the quality of non instrumental meteorological records in absence of instrumental observations to perform a calibration. In these cases it is mandatory to envision different approaches to assess the climatic signal in a reconstruction. This work is aimed to test the consistency of a snow frequency reconstruction in the central Argentinean Andes by studying the synoptic patterns related to the occurrence of precipitation in this area. While the original reconstruction covers the period between 1885 and 1996, the insufficiency of overlapping instrumental data limited the calibration to a short 15-year interval. In this paper we evaluate the performance of the reconstructed series for the entire 45-year period between 1958 and 1996 by analyzing the displacement in the jet stream and the patterns of geopotential height related to anomalies in the reconstructed snow frequency series. Previous works have linked the precipitation in the central Andes to the ENSO through the Pacific South American mode. We also have found this connection between ENSO and the reconstructed precipitation. Finally, it is shown that the ENSO relationship is the cause of a significant link between the precipitation anomalies in the central Argentinean Andes and the ice extent around the Antarctic Peninsula., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

©2003 American Meteorological Society. The authors wish to thank C. Appenzeller, E. Cook, J. Luterbacher, C. J. Proctor, and F. S. Rodrigo for providing their proxy NAO reconstructions. This study is supported by the Spanish Comisión Interministerial de Ciencia y Tecnología under Grant CLI98-0649., Records of taxes collected during the seventeenth and eighteenth centuries contribute to understanding of climatic variability of the subtropical North Atlantic region. Historical documentary sources in the Canary Islands have been used to construct cereal production series for the period 1595–1836. The cereal growth period in this region covers essentially the rainy season, making these crops adequate to characterize the annual precipitation. A proxy for the Islands' rainfall based on the historical series of wheat and barley production has been constructed and assessed by using two independent series of dry and wet years. The spectral analysis of the crop production reveals a strong non stationary behavior. This fact, along with the direct comparison with several reconstructed and instrumental North Atlantic Oscillation series, suggests the potential use of the reconstructed precipitation as a proxy for this climatic oscillation during preinstrumental times., Comisión Interministerial de Ciencia y Tecnología (CICYT), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2009 GADAM Centre, Institute of Physics, Silesian University of Technology. All rights reserved. We wish show our gratitude to the persons that help in the acquisition of trunk sections of Holm Oaks in special to Maderas Bautista from Alcántara area. Special mention must be for D. Justo Hernández Morgado from Roca de la Sierra (Badajoz) who gave the total set of trunks used from this area. Thanks to Troy Nahumko and Adrian Birtwistle for their support on the English version. We also thank two anonymous referees that help during the initial version of the manuscript. R. García Herrera is partially supported by the EU CIRCE project (EU IP 036961). D. Patón was supported by a "Salvador de Madariaga" grant of the Spanish Minister of Science and Technology. The Spanish National Institute of Meteorology kindly provided the meteorological data., A total of 47 trunk sections from Holm Oak (Quercus ilex subsp. ballota Desf) trees growing at two different sites at the Extremadura region (SW Spain) were considered in the computation of a regional tree-ring chronology useful to interpret the tree-ring/Mediterranean climate relationships. This is the first dendroclimatological research of Holm Oaks conducted to reveal its potential use as a climatic proxy. The obtained tree-ring chronologies were compared with climatic parameters based on monthly, seasonal and annual rainfall, and monthly maximum, minimum and average temperature. The best correlations were obtained with maximum temperatures during the period between previous winter and early spring. Influence of rainfall was less relevant. Growth of this species indicates a typical bimodal (spring and autumn) strategy that avoids low winter temperatures and summer drought. Despite some technical difficulties recognizing tree rings in Holm Oaks, its good sensitivity to climate variability and its wide distribution and longevity (~800 years), allow us to consider this species as a good candidate for temperature reconstructions in the Mediterranean Basin., Unión Europea. FP6, Ministerio de Ciencia y Tecnología (MCYT), España, Instituto Nacional de Meteorología (INM), España, Agencia Estatal de Meteorología del Gobierno de España (AEMET), Proyecto Salvador de Madariaga, PROJECT (Climate Change and Impact Research: the. Mediterranean Environment), UE, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Springer 2005. The authors thank the three reviewers who helped to improve the clarity of the work. D. Wheeler kindly revised the manuscript., Records of wind strength taken onboard Spanish and French ships during the 1750-1850 period have been digitized and examined using content analysis techniques to derive the equivalent wind strength in terms of the current Beaufort scale, this conversion being a key step in any attempt to compare ancient records with modern climatologies. During the analysis it was evident that Spanish and French officers used a great number of different terms to describe the wind force. However, when the records are analyzed and homogenized, a broadly common and essentially narrow vocabulary was identified, indicating that, at this period, a great effort had been made to regulate the maritime language. Using contemporary dictionaries and navigation manuals, an equivalence was established between the original wind force terms and the Beaufort scale., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2005 Elsevier B.V. The authors wish to thank the INM for providing the CG lightning data used in the development of the paper. Our thanks also to the two anonymous referees of this paper for their interesting suggestions and comments., In this paper cloud-to-ground (CG) lightning flashes of 33 Mesoscale Convective Systems (MCSs) over the Western Mediterranean area are analyzed. Mean values of 22% for the positive CG ratio, 1.1 (2.4) for positive (negative) CG multiplicity, 17 kA (22.6 kA) of peak current for the positive (negative) CG flashes and a mean flash rate of around 13 min(-1) are obtained. The percentage of positive CGs and the multiplicity of negative CG are higher, while the mean peak currents are lower than in previous studies on MCSs. A more detailed case analysis reveals that there are great differences among the CG characteristics of MCSs. The life cycle of CG lightning associated with MCSs is also analyzed. The growing stages of MCSs are characterised by high CG lightning activity. The positive CG flash rate generally reaches a maximum before the negative CG flash rate does. In both cases the peak is recorded before or when MCSs show the largest area. Maximum flash rate and densities coincide with the area where the MCS shows the minimum cloud-top temperatures and therefore shows highest vertical development., 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

© European Geosciences Union 2005. NCEP/NCAR reanalysis data were obtained from the Climate Prediction Centre. The Atlantic-European window used here was kindly provided by Ian Harris and David Viner from the Climatic Research Unit. The authors would like to acknowledge Isabel Trigo from CGUL for helpful suggestions on a earlier version of this paper. Spanish Instituto Nacional de Meteorología provided Meteorological data from Madrid. Two anonimous reviewers provided helpful comments which improved considerably the original manuscript. Topical Editor O. Boucher thanks two referees for their help in evaluating this paper., This paper examines the effect of extreme summer temperatures on daily mortality in two large cities of Iberia: Lisbon (Portugal) and Madrid (Spain). Daily mortality and meteorological variables are analysed using the same methodology based on Box-Jenkins models. Results reveal that in both cases there is a triggering effect on mortality when maximum daily temperature exceeds a given threshold (34°C in Lisbon and 36°C in Madrid). The impact of most intense heat events is very similar for both cities, with significant mortality values occurring up to 3 days after the temperature threshold has been surpassed. This impact is measured as the percentual increase of mortality associated to a V C increase above the threshold temperature. In this respect, Lisbon shows a higher impact, 31%, as compared with Madrid at 21%. The difference can be attributed to demographic and socio-economic factors. Furthermore, the longer life span of Iberian women is critical to explain why, in both cities, females are more susceptible than males to heat effects, with an almost double mortality impact value. The analysis of Sea Level Pressure (SLP), 500 hPa geo-potential height and temperature fields reveals that, despite being relatively close to each other, Lisbon and Madrid have relatively different synoptic circulation anomalies associated with their respective extreme summer temperature days. The SLP field reveals higher anomalies for Lisbon, but extending over a smaller area. Extreme values in Madrid seem to require a more western location of the Azores High, embracing a greater area over Europe, even if it is not as deep as for Lisbon. The origin of the hot and dry air masses that usually lead to extreme heat days in both cities is located in Northern Africa. However, while Madrid maxima require wind blowing directly from the south, transporting heat from Southern Spain and Northern Africa, Lisbon maxima occur under more easterly conditions, when Northern African air flows over the cen, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Inter-Research 2005. This study was partially supported by the Risk Prediction Initiative, under Grant RPI02-2-009. The authors thank F. Koek, for providing a copy of the original Selga (1935) paper, and Chris Landsea and 2 anonymous reviewers, whose comments helped us to improve the manuscript., A chronology of typhoons and storms in the Western North Pacific is presented, based on the previous work of Miguel Selga, a former director of the Manila Observatory. It includes data about 863 typhoons, storms and depressions over the western Pacific area between 1901 and 1934. The chronology provides information covering a wide area, from Guam to the Gulf of Tonkin and from the equator to Japan. The resulting typhoon series has been included in a database, which is freely accessible, and annual typhoon occurrence and trajectories are also shown. A comparison of the typhoon passage frequency over the Philippine area with a previously available chronology was made to assure the validity of Selga's observations, showing good agreement., Risk Prediction Initiative (RPI2.0), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2001 American Meteorological Society. The authors wish to thank to the two anonymous referees for their useful comments, which have contributed to the improvement of the quality and presentation of this work. This study is supported by the Spanish Comisión Interministerial de Ciencia y Tecnologia under Grant CLI98-0649., The aim of this paper is to investigate the relationship between the Canary Island rainfall and the Atlantic large-scale circulation, characterized by the North Atlantic oscillation (NAO) index. The Canary Islands are located in the Atlantic subtropical belt under the direct influence of the Azores high and the trade winds. Their steep orography makes the islands very sensitive to small variations in a synoptic situation, thus providing an excellent natural observatory for the North Atlantic variability associated with changes in pressure patterns. A significant relationship between rainfall and the NAO is found for five of the seven Canary Islands. In order to characterize the physical mechanisms involved, a set of automatic objective techniques for identification and detection of disturbances is applied to the 1000- and 500- hPa geopotential from the NCEP-NCAR reanalysis for the period from 1955 to 1998. This method allows for the identification and detection of four main synoptic systems-either at the surface or at 500 hPa-that are responsible for 80% of the precipitation over the Canary Islands: Atlantic surface lows (ASLs), 500-hPa lows (UALs), 500- hPa troughs over the Canary Islands (TROs), and deep Atlantic lows (DALs), which affect the entire troposphere. Three of the detected disturbances (ASLs, TROs, and DALs) exhibit a dipolar structure with a low pressure center over 35 degreesN associated with a positive anomaly at higher latitudes, resembling the NAO negative pattern. The analysis of the variability of the disturbance occurrence and the changes in their associated anomaly patterns shows that deeper and more frequent ASLs and TROs affect the Canary Islands during the negative phase of the NAO. However, UAL disturbances are less frequent, and DALs do not exhibit significant variations with the NAO phase. The standard deviation of the 2.5-8-day bandpass-filtered geopotential height shows that the maximum variability associated with the NAO occurs over th, Comisión Interministerial de Ciencia y Tecnologia (CICYT), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2007 American Meteorological Society. This work was partially supported by the Spanish Ministry of Science through Grant HP 2004-0039. We also thank the Instituto Nacional de Meteorología (INM) for providing the precipitation data for the Spanish stations. R. M. Trigo was supported by Projects VAST (Variability of Atlantic Storms and their impact on land climate), Contract POCTI/CTA/ 46573/2002, and CLIMAAT (Climate and Meteorology of the Atlantic Archipelagos), Interreg IIIb A3/2.3, both cofinanced by the EU under program FEDER. Three anonymous reviewers also helped to improve this manuscript., The 2004/05 hydrological year (October 2004 to September 2005) was characterized by intense dry conditions affecting most of western Europe (35 degrees-55 degrees N and 10 degrees W-10 degrees E). In Iberia the drought affected every month of this period, with the southern half of Iberia receiving roughly 40% of the usual precipitation by June 2005. Moreover, this episode stands as the driest event in the last 140 yr, producing major socioeconomic impacts particularly due to the large decrease in hydroelectricity and agricultural production in both Iberian countries (Portugal and Spain). To assess the atmospheric submonthly circulation associated with this drought an Eulerian [weather types (WTs)] and a Lagrangean (objective storm tracks) analysis were combined. There was a dramatic drop in "wet" WT frequency during winter, with less than 50% of the normal value, and a corresponding increase of "dry" WTs. The storm-track analysis reveals an impressive northward displacement of cyclone trajectories in the North Atlantic sector in winter months, resulting in an almost complete absence of cyclones crossing Iberia and western Europe. At the monthly scale, the intense drought in Iberia was due to a combination of different physical mechanisms. First, the scarce precipitation observed between November 2004 and January 2005 was associated with positive North Atlantic Oscillation (NAO) indexes for these months. In February, the East Atlantic (EA) pattern seems to be the main driver. In March neither the negative NAO (-1.8) nor the positive EA (1.1) are capable of explaining the large negative precipitation anomalies. However, it is shown that during March 2005, an intense and anomalous blocking was displaced southward of its usual location, inhibiting the occurrence of precipitation over Iberia and leading to a negative NAO index anomalously associated with low precipitation records., Spanish Ministry of Science, EU, program FEDER., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2005 American Meteorological Society. This work was supported by the Spanish Ministry and Science and Technology (MCYT) under Grant REN2002-04558-C04-02 and by the Galician Programme of Research and Development under Grant PGIDIT03PXIC38301PN. The authors thank three anonymous reviewers for their helpful comments and suggestions., This study presents the first multidecadal climatology of cutoff low systems in the Northern Hemisphere. The climatology was constructed by using 41 yr (1958-98) of NCEP-NCAR reanalysis data and identifying cutoff lows by means of an objective method based on imposing the three main physical characteristics of the conceptual model of cutoff low (the 200-hPa geopotential minimum, cutoff circulation, and the specific structure of both equivalent thickness and thermal front parameter fields). Several results were confirmed and climatologically validated: 1) the existence of three preferred areas of cutoff low occurrence (the first one extends through southern Europe and the eastern Atlantic coast, the second one is the eastern North Pacific, and the third one is the northern China-Siberian region extending to the northwestern Pacific coast; the European area is the most favored region); 2) the known seasonal cycle, with cutoff lows forming much more frequently in summer than in winter; 3) the short lifetime of cutoff lows, most cutoff lows lasted 2-3 days and very few lasted more than 5 days; and 4) the mobility of the system, with few cutoff lows being stationary. Furthermore, the long study period has made it possible (i) to find a bimodal distribution in the geographical density of cutoff lows for the European sector in all the seasons (with the exception of winter), a summer displacement to the ocean in the American region, and a summer extension to the continent in the Asian region, and (ii) to detect northward and westward motion especially in the transitions from the second to third day of occurrence and from the third to fourth day of occurrence. The long-term cutoff low database built in this study is appropriate to study the interannual variability of cutoff low occurrence and the links between cutoff lows and jet stream systems, blocking, or major modes of climate variability as well as the global importance of cutoff low in the stratosphere-troposphere exch, Ministerio de Ciencia y Tecnología (MICYT), España, Comunidad Autónoma de Galicia, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2008 American Meteorological Society. We gratefully acknowledge librarians at historical libraries and societies for help in collecting historical data. We also thank Henry Díaz, Ramón Pérez, and an anonymous reviewer for their comments. The Spanish Ministry of Science and Education provided partial support through Grant MEC.CGL2005-25107-E/CLI. Cary Mock’s contribution is supported by NSF Grant ATM-0502105., This paper documents a rare spell of severe weather in Spain that took place during the mid-nineteenth century when a tropical storm struck the southwest of the country on 29 October 1842. The use of a variety of independent documentary sources has provided unprecedented scope for the analysis of this event, allowing it to be set within its wider context, and for a judgement to be made on its tropical origin. The evidence suggests that this was similar, though stronger, to the more recent Hurricane Vince, which made landfall in Spain on 10 October 2005. This case study not only places Hurricane Vince, suggested at the time to have been unique, in its more proper long-term context, but it also demonstrates how documentary sources can improve our wider understanding of climate dynamics during historical times in the Atlantic basin., Ministerio de Educación y Ciencia (MEC), España, National Science Foundation (NSF), EE.UU., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2010 by the American Geophysical Union. NCEP reanalysis data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, at their Web site (http://www.cdc.noaa.gov/). The Ufficio Idrografico of Venice provided sea level data. Solar data were obtained from the National Geophysical Data Center of the NOAA at their Web site (www.ngdc.noaa.gov/stp/SOLAR/ftpsolarradio.html). This study was partially supported by EU Sixth Framework Program (CIRCE) contract 036961 (GOCE) and the ENAC project (PTDC/AAC-CLI/103567/2008) funded by the IDL-FFCUL. We also acknowledge the contribution from the ESF MedCLIVAR program., This study explores the long-term frequency variability of high-surge events (HSEs) in the North Adriatic, the so-called acqua alta, which, particularly during autumn, cause flooding of the historical city center of Venice. The period 1948-2008, when hourly observations of sea level are available, is considered. The frequency of HSEs is correlated with the 11 year solar cycle, solar maxima being associated with a significant increase in the October-November-December HSE frequency. The seasonal geopotential height pattern at 1000 hPa (storm surge pattern; SSP) associated with the increased frequency of HSEs is identified for the whole time period and found to be similar to the positive phase of the main variability mode of the regional atmospheric circulation (empirical orthogonal function 1; EOF1). However, further analysis indicates that solar activity modulates the spatial patterns of the atmospheric circulation (EOF) and the favorable conditions for HSE occurrence (SSP). Under solar maxima, the occurrence of HSEs is enhanced by the main mode of regional atmospheric variability, namely, a large-scale wave train pattern that is symptomatic of storm track paths over northern Europe. Solar minima reveal a substantially different and less robust SSP, consisting of a meridionally oriented dipole with a preferred southward path of storm track activity, which is not associated with any dominant mode of atmospheric variability during low-solar periods. It is concluded that solar activity plays an indirect role in the frequency of HSEs by modulating the spatial patterns of the main modes of atmospheric regional variability, the favorable patterns for HSE occurrence, and their mutual relationships, so that constructive interaction between them is enhanced during solar maxima and inhibited in solar minima., EU, IDL-FFCUL, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

Copyright 2005 by the American Geophysical Union. We would like to thank J. Luterbacher and two anonymous reviewers for their helpful comments and suggestions. The authors are in debt with C. Gouveia for her technical support., The summer of 2003 was characterised by exceptionally warm weather in Europe with the average temperature exceeding that of any previous summer over the last 500 years. The seasonal 2003 summer temperature for central Europe was beyond the historical distribution range and could bear a closer resemblance with climate change scenarios for late XXI century. Nevertheless, it was the heatwave that occurred between the 1st and the 15th of August 2003 that had a major impact in excessive mortality rates throughout Europe, with catastrophic amplitude in France. Here we show, on a daily basis, when and where the magnitude and spatial extent of this heatwave episode has surpassed previous historical maxima, and that this episode is associated with an equally maximum blocking pattern over western Europe. Finally we show that surface and low troposphere air temperature anomalies are particularly well associated with the increased mortality rates in France., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2007 by the American Geophysical Union. This work was supported by UNICAJA. The authors wish to thank M. J. Puertas for abstraction of the original reports; A. Gullón for helping in the historical interpretation; M. Barriendos, P. Jones, G. Können and D. Wheeler for the fruitful discussion about the interpretation of the results; the Spanish Meteorological Institute; and C. Camacho for useful information about the characteristics of the Tavira tower. Finally, the two anonymous reviewers are thanked for their helpful comments., A new documentary source of data for wind, atmospheric pressure and air temperature for the city of Cadiz (southern Spain) has been abstracted, analyzed and compared with present-day data. Wind records cover the period 1806-1852 with three observations per day. Instrumental pressure and temperature cover the period 1825-1852. While the historical pressure series shows average values very close to that found for the period 1971-2000, temperature shows a large asymmetric seasonal warming, with increments in the order of 2 degrees C for the winter months and almost no change for summer. Wind measurements have been transformed into their numerical equivalents and then compared with present-day values. The analysis shows that the numerical estimation of ancient wind forces observed at Cadiz, while providing a robust climatic signal, has a strong bias to larger values than their instrumental equivalents. Despite the uncertainties involved in the interpretation of early wind series, this effect could be related to the recording of "average wind gusts" rather than average winds as measured by today's anemometers. In consequence, wind climatologies based on historical data, which recently are becoming available to the scientific community, should be used carefully., UNICAJA, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 American Meteorological Society. We gratefully acknowledge Ann Wakefield, Howard Margot, and many others for help in obtaining archival data, and Dennis Wheeler, Lesley-Ann Dupigny-Giroux, Richard Campanella, David Bastian, Vicky Slonosky, Anuj Patwardhan, Stephanie Dodds, and three reviewers for help and discussions in various stages of the research. This research is supported by NSF Grant ATM-0502105., Major hurricanes are prominent meteorological hazards of the U.S. Atlantic and Gulf coasts. However, the official modern record of Atlantic basin tropical cyclones starts at 1851, and it does not provide a comprehensive measure of the frequency and magnitude of major hurricanes. Vast amounts of documentary weather data extend back several centuries, but many of these have not yet been fully utilized for hurricane reconstruction. These sources include weather diaries, ship logbooks, ship protests, and newspapers from American, British, and Spanish archives. A coordinated effort, utilizing these historical sources, has reconstructed a major hurricane in August 1812, which is the closest to ever pass by New Orleans, Louisiana, including Hurricane Katrina. The storm became a tropical depression in the Caribbean Sea, passed south of Jamaica as a tropical storm, and then strengthened to hurricane strength in the Gulf of Mexico. It made landfall about 65 km southeast of New Orleans and passed just to the west of the city. Historical storm surge and damage reports indicate it as a major hurricane at landfall. Given that conditions during 1812 include having lower sea level, higher land elevation prior to human-induced subsidence, and more extensive wetlands, a recurrence of such a major hurricane would likely have a greater detrimental societal impact than that of Hurricane Katrina. The 1812 hurricane study provides an example of how historical data can be utilized to reconstruct past hurricanes in a manner that renders them directly comparable with those within our modern record., National Science Foundation (NSF), EE.UU., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2008 New York Academy of Sciences. European Meteorology Society Annual Meeting (7º. 2007. El Escorial, Spain). European Conference on Applications of Meteorology (8º. 2007. El Escorial, Spain), The quasibiennial oscillation (QBO) dominates the variability of the equatorial stratosphere and also affects the circulation and temperature of the extratropical region. In this paper we review previous work showing that the mid- to high-latitude circulation is weaker (stronger) when QBO easterlies (westerlies) dominate in the low equatorial stratosphere. The accepted explanation for the extratropical QBO signature is based on the QBO modulation of upward propagating planetary Rossby waves. This mechanism is consistent with the strong seasonality observed in the extratropical QBO. The largest QBO signature in the northern extratropical stratosphere occurs during winter when the dominating westerly wind allows the penetration of planetary waves in the northern stratosphere. However, during the southern winter, planetary waves do not disrupt the southern stratospheric vortex and the largest QBO signature is found during the late spring (November). To further illustrate these mechanisms, we analyze the QBO signature on the mid- to high-latitude circulation of the stratosphere using data from the ERA-40 reanalysis. The extratropical signature in both hemispheres is evaluated as a function of the latitude-height structure of the zonal wind in the tropical region in order to determine how the extratropical response depends on the vertical phase structure of the tropical QBO. We also analyze the QBO impact on planetary wave activity in order to determine how this modulation can explain the observed extratropical QBO signal., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 American Meteorological Society. The Spanish Science and Technology Department supported this study trough the VALIMOD (Climatic Validation of Conceptual Models) project (REN2002-04558-C04-01)., In this paper a 55-yr (1948-2002) Northern Hemisphere blocking climatology is presented. Traditional blocking indices and methodologies are revised and a new blocking detection method is designed. This algorithm detects blocked flows and provides for a better characterization of blocking events with additional information on blocking parameters such as the location of the blocking center, the intensity, and extension. Additionally, a new tracking procedure has been incorporated following simultaneously the individual evolution of blocked flows and identifying coherently persistent blocked patterns. Using this method, the longest known Northern Heinisphere blocking climatology is obtained and compared with previous studies. A new regional classification into four independent blocking sectors has been obtained based on the seasonally preferred regions of blocking formation: Atlantic (ATL), European (EUR), West Pacific (WPA), and East Pacific (EPA). Global and regional blocking characteristics have been described, examining their variability from the seasonal to interdecadal scales. The global long-term blocking series in the North Hemisphere showed a significant trend toward weaker and less persistent events, as well as regional increases (decreases) in blocking frequency over the WPA (ATL and EUR) sector. The influence of teleconnection patterns (TCPs) on blocking parameters is also explored, being confined essentially to wintertime, except in the WPA sector. Additionally, regional blocking parameters, especially frequency and duration, are sensitive to regional TCPs, supporting the regional classification obtained in this paper. The ENSO-related blocking variability is evident in blocking intensities and preferred locations but not in frequency. Finally, the dynamical connection between blocking occurrence and regional TCPs is examined through the conceptual model proposed by Charney and DeVore. Observational evidence of a dynamical link between the asymmetrical tem, Spanish Science and Technology Department, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© John WiIley & Sons LTD. This work was supported by the research framework established between STREAM group at University Complutense of Madrid and Iberdrola Renovables Energia S.A., through a fellowship programme under Art. 83 of L.O.U. Two anonymous reviewers contributed to improve the original manuscript., The study of the wind power output variability comprises different time scales. Among these, low-frequency variations can substantially modify the performance of a wind power plant during its lifetime. In recent years, other temporal scales such as the short-term variability or the climatological conditions of wind and the corresponding generated power have been investigated in depth. However, the study of longer decadal and multidecadal variations is still in its early stages. In this work, the wind power output long-term variability is analysed for two locations in Spain, during the period 1871-2009. This is attained by computing the annual wind speed probability density functions derived from an ensemble of atmospheric sea level pressure data set through a statistical downscaling based in evolutionary algorithms. Results reveal significant trends and periodicities in multidecadal bands including 13, 25 and 46years, as well as significant differences among both sites. The impact of the leading large-scale circulation patterns (NAO, EA, SCAND and AMO) on wind power output and its stationarity is analysed. Results on both locations show non-stationary significant and opposite seasonal couplings with these forcings. Finally, the long-term variability of the reconstructed Weibull parameters of the annual wind speed distributions is used to derive a linear model to estimate the annual wind power., STREAM Group (University Complutense of Madrid - UCM), Iberdrola Renovables Energia S.A., Universidad Complutense de Madrid (UCM), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

Copyright 2008 by the American Geophysical Union. This work was partly funded by the Spanish National Research Project TRODIM MEC-CGL2007-65891-C05-04-CLI., The seasonality of the quasi-biennial oscillation (QBO) and its secondary circulation is analyzed in the European Reanalysis (ERA-40) and Middle Atmosphere European Centre Hamburg Model (MAECHAM5) general circulation model data sets through the multitaper method-singular value decomposition (MTM-SVD). In agreement with previous studies, the results reveal a strong seasonal dependence of the QBO secondary circulation. This is characterized by a two-cell structure symmetric about the equator during autumn and spring. However, anomalies strongly weaken in the summer hemisphere and strengthen in the winter hemisphere, leading to an asymmetric QBO secondary circulation characterized by a single-cell structure displaced into the winter hemisphere during the solstices. In ERA-40, this asymmetry is more pronounced during the northern than during the southern winter. These results provide the first observation of the QBO secondary circulation asymmetries in the ERA-40 reanalysis data set across the full stratosphere and the lower mesosphere, up to 0.1 hPa. The MTM-SVD reconstruction of the seasonal QBO signals in the residual circulation and the QBO signals in Eliassen Palm (EP) flux divergences suggest a particular mechanism for the seasonal asymmetries of the QBO secondary circulation and its extension across the midlatitudes. The analysis shows that the QBO modulates the EP flux in the winter hemispheric surf zone poleward of the QBO jets. The zonal wind forcing by EP flux divergence is transformed by the Coriolis effect into a meridional wind signal. The seasonality in the stratospheric EP flux and the hemispheric differences in planetary wave forcing cause the observed seasonality in the QBO secondary circulation and its hemispheric differences., Proyecto TRODIM (Diagnosis y modelización de la tropopausa extratropical), MEC, Ministerio de Educación y Ciencia (MEC), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 Royal Meteorological Society. This study is supported by the Spanish Comision Interministerial de Ciencia y Tecnologia under grant CLI98-0649. The Spanish Instituto Nacional de Meteorología provided the data for this study. The authors wish to thank the two anonymous referees for their useful comments, which contributed to improving the quality and presentation of this work., A strong decreasing trend in the Canary Islands' precipitation is detected by studying daily rainfall time series for the second half of the 20th century. An analysis of the extreme events shows that this trend is due mainly to a decrease in the upper percentiles of the precipitation distribution. The results suggest that local factors play a fundamental role on extreme event behaviour., Spanish Comisión Interministerial de Ciencia y Tecnología, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Springer-Verlag Berlin Heidelberg 2015. The authors wish to acknowledge Ricardo Trigo and one anonymous reviewer for their detailed and helpful comments to the original manuscript. The data for this paper are available at Spanish National Research Council repository (http://sac.csic.es/spei/database.html), at Climate Research Unit (http://www.cru.uea.ac.uk/cru/data/nao/) and the Climate Prediction centre of the NOAA (http://www.cpc.ncep.noaa.gov/data/teledoc/telecontents.shtml). This work was supported by the research project CGL2014-52135-C3-1-R and Red de variabilidad y cambio climático RECLIM (CGL2014-517221-REDT) financed by the Spanish Commission of Science and Technology and FEDER, Ephyslab (UVIGO-CSIC Associated Unit) and "LIFE12 ENV/ES/000536-Demonstration and validation of innovative methodology for regional climate change adaptation in the Mediterranean area (LIFE MEDACC)" financed by the LIFE programme. C. A-M received a postdoctoral fellowship #JCI-2011-10263. Iberdrola Renovable provided partial support from contracts., This paper analyses the influence of different atmospheric circulation indices on the multi-scalar drought variability across Europe by using the Standardized Precipitation Evapotranspiration Index (SPEI). The monthly circulation indices used in this study include the North Atlantic oscillation (NAO), the East Atlantic (EA), the Scandinavian (SCAN) and the East Atlantic-Western Russia (EA-WR) patterns, as well as the recently published Westerly Index (WI), defined as the persistence of westerly winds over the eastern north Atlantic region. The results indicate that European drought variability is better explained by the station-based NAO index and the WI than by any other combination of circulation indices. In northern and central Europe the variability of drought severity for different seasons and time-scales is strongly associated with the WI. On the contrary, the influence of the NAO on southern Europe droughts is stronger than that exerted by the WI. The correlation patterns of the NAO and WI with the SPEI show a spatial complementarity in shaping drought variability across Europe. Lagged correlations of the NAO and WI with the SPEI also indicate enough skill of both indices to anticipate drought severity several months in advance. As long as instrumental series of the NAO and WI are available, their combined use would allow inferring European drought variability for the last two centuries and improve the calibration and interpretation of paleoclimatic proxies associated with drought., Ministerio de Economía e Innovación (MICINN), Red de variabilidad y cambio climático (RECLIM), Iberdrola, LIFE Programme (UE), Comisión Interministerial de Ciencia y Tecnología (CICYT), Estrategia Española de Ciencia y Tecnología y de Innovación 2013-2020, Fondo Europeo de Desarrollo Regional (FEDER), Environmental Physics Laboratory EPHYSLAB, Universidad de Vigo, Consejo Superior de Investigaciones Científicas (CSIC), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

©2007 American Meteorological Society. The authors thank M. Molloy of Elkridge, Maryland, for translation of the French document and Joe D. Elms and Larry Nicodemus, National Climatic Data Center, Asheville, North Carolina, for providing the modern Barbados data. Gill Jackson of The Royal Society generously provided assistance with the Sharpe manuscript record., The first barometers in the Americas were provided by the Royal Society of London in 1677 to correspondents in the Caribbean Island of Barbados. Colonel William Sharpe of Barbados was the first person in the Americas to make daily observations of the weather using a meteorological instrument (other than a wind vane) and made the first known measurements of barometric pressure within the circulation of a hurricane on 12 August 1680. His record provides new insight into the early history of the barometer and early perceptions of tropical weather, vindicates the hypothesis that the barometer would prove useful in detecting hurricanes, and contributes to Edmund Halley's understanding of the empirical distinctions between the Tropics and temperate zones. Sharpe's name and contributions, previously unknown to the meteorological community, can now be properly recognized., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2008 New York Academy of Sciences. European Meteorology Society Annual Meeting (7. 2007. El Escorial). European Conference on Applications of Meteorology (8. 2007. El Escorial, Spain). This work has been funded by the Spanish Ministry of Education and Science and the Fulbright Commission in Spain. The WACCM3 simulations discussed here were carried out at the Barcelona Supercomputing Center, Barcelona, Spain, and at the National Center for Atmospheric Research (NCAR), Boulder, CO, USA. NCAR is sponsored by the US National Science Foundation., Although the El Nino-Southern Oscillation (ENSO) is a tropospheric phenomenon, its effects are also observed in the stratosphere. Traditionally, the study of ENSO above the troposphere has been difficult because of the lack of global observations at high altitudes and also because of the presence of other sources of variability whose signals are difficult to disentangle from ENSO effects. Recent work with general circulation models that isolate the ENSO signal have demonstrated its upward propagation into the stratosphere. Here we review the literature in this field and show results from the most recent version of the Whole Atmosphere Community Climate Model to illustrate the propagation and the mechanisms whereby the signal manifests itself in the stratosphere. The ENSO signal propagates upward to about 40 km by means of large-scale Rossby waves. The propagation is strongly influenced by the zonal mean zonal winds. Most of the strong ENSO events tend to peak in the boreal winter and so the ENSO signal is observed mainly at high latitudes during the Northern Hemisphere winter where the winds are westerly and allow Rossby wave propagation. The ENSO signal is also identified at polar latitudes in the Northern Hemisphere winter in the form of warmer temperatures and weaker winds during a strong El Nino event. This signal shows a zonally homogeneous behavior from the intensification of the stratospheric meridional circulation (in which air rises in the tropics and moves toward the winter pole where it descends) forced by anomalous propagation and dissipation of Rossby waves at middle latitudes during strong ENSO events., Spanish Ministry of Education and Science, Fulbright Commission in Spain, US National Science Foundation, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 StudiaGeo s.r.o., Equivalent temperature based in the NCEP/NCAR reanalysis database has been used as a simultaneous measure of temperature and humidity. Its variations during the 1958-1998 added to the effect of the inclusion of satellite data during the late seventies have been analyzed. An increase of the globally averaged equivalent temperature has been detected, the trend has been considerably greater during the first half of the study period and significant differences can be found between continental and oceanic areas. The relation of the trend with four of the main modes of climate variability has been assessed. The North Atlantic Oscillation and the Artic Oscillations are closely related to the equivalent temperature over the North Atlantic basin, extending toward Northern Asia in the second case. El Nino/Southern Oscillation and the Antarctic Oscillation seem to have a more global effect., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2004 American Meteorological Society. The National Center for Atmospheric Research is sponsored by the National Science Foundation. We thank Jon Eischeid for his help in obtaining the MSU data used in this paper, and Henry Diaz, Dan Marsh, Bill Randel, and Anne Smith for discussions and suggestions on the original manuscript., The El Niño-Southern Oscillation (ENSO) signal in the troposphere and lower stratosphere was investigated using Microwave Sounding Unit (MSU) data for the period 1979-2000. Empirical orthogonal functions (EOFs) were computed separately for zonal-mean and eddy temperatures in the Tropics and shown to provide a compact, physically intuitive description of ENSO that captures many of the details of its inception and evolution. Regressions of the MSU data on the principal components (PCs) of the tropical EOFs were then used to estimate the global signal of ENSO. The results show that ENSO accounts for over two-thirds of the temperature variability in the tropical troposphere, where its signature is composed of distinct zonal-mean and eddy patterns whose evolution is not simultaneous. In the tropical stratosphere, and outside the Tropics, ENSO explains a much smaller fraction of the variance (similar to10%), and manifests itself purely in the form of eddy anomaly patterns. The PCs of the eddy EOFs of the tropical stratosphere are almost perfectly correlated with those of the troposphere, suggesting that together the EOFs describe the vertical structure of equatorial waves. Volcanic eruptions and the quasi-biennial oscillation (QBO) are responsible for most of the variability (similar to87%) of the tropical lower stratosphere, and this variability is uncorrelated with ENSO; in the tropical troposphere, the effect of volcanic eruptions is detectable but small, accounting for about 3% of the variance., National Science Foundation, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Author(s) 2014. CC Attribution 3.0 License. The proposal for this special issue has been initiated within the CIRCE (EU-fp6 project, contract number 036961) and supported by the MedCLIVAR network (www.medclivar.eu)., There is an increasing interest of scientists on climate extremes. A progressively larger number of papers dealing with climate issues have been produced in the past 15 yr, and those dealing with extremes have increased at an even faster pace. The number of papers on extremes in the Mediterranean follows this overall trend and confirms how extremes are perceived to be important by the scientific community and by society. This special issue (which is mainly related to activities of the MedCLIVAR (Mediterranean CLImate VARiability and Predictability) and CIRCE (Climate Change and Impact Research: the Mediterranean Environment) projects), contains thirteen papers that are representative of current research on extremes in the Mediterranean region. Five have precipitation as its main target, four temperature (one paper addresses both variables), and two droughts; the remaining papers consider sea level, winds and impacts on society. Results are quite clear concerning climate evolution toward progressively hotter temperature extremes, but more controversial for precipitation, though in the published literature there are indications for a future increasing intensity of hydrological extremes (intense precipitation events and droughts). Scenario simulations suggest an attenuation of extreme storms, winds, waves and surges, but more results are requested for confirming this future change., MedCLIVAR Project (Mediterranean Climate Variability and Predictability), Unión Europea (UE), CIRCE (Climate change and impact research project), UE, Sixth Framework Programme (FP6), UE, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2015 American Meteorological Society. This study was supported by the Spanish Ministry of Science and Innovation (MCINN) through the MATRES (CGL2012-34221) project and the EU FP7 program through the StratoClim project (603557). We thank W. Seviour and D. Mitchell for providing the onset dates of the SSWs detected with their definition in the ERA reanalyses. We thank A. Butler and two anonymous reviewers for their useful comments and recommendations., Sudden stratospheric warmings (SSWs) are characterized by a pronounced increase of the stratospheric polar temperature during the winter season. Different definitions have been used in the literature to diagnose the occurrence of SSWs, yielding discrepancies in the detected events. The aim of this paper is to compare the SSW climatologies obtained by different methods using reanalysis data. The occurrences of Northern Hemisphere SSWs during the extended-winter season and the 1958-2014 period have been identified for a suite of eight representative definitions and three different reanalyses. Overall, and despite the differences in the number and exact dates of occurrence of SSWs, the main climatological signatures of SSWs are not sensitive to the considered reanalysis.The mean frequency of SSWs is 6.7 events decade^-1, but it ranges from 4 to 10 events, depending on the method. The seasonal cycle of events is statistically indistinguishable across definitions, with a common peak in January. However, the multidecadal variability is method dependent, with only two definitions displaying minimum frequencies in the 1990s. An analysis of the mean signatures of SSWs in the stratosphere revealed negligible differences among methods compared to the large case-to-case variability within a given definition.The stronger and more coherent tropospheric signals before and after SSWs are associated with major events, which are detected by most methods. The tropospheric signals of minor SSWs are less robust, representing the largest source of discrepancy across definitions. Therefore, to obtain robust results, future studies on stratosphere-troposphere coupling should aim to minimize the detection of minor warmings., Unión Europea. FP7, Ministerio de Ciencia e Innovación (MICINN), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2003 by the American Geophysical Union., The spatiotemporal evolution of the zonal wind in the stratosphere is analyzed based on the use of the NCEP reanalysis (1958-2001). MultiTaper Method-Singular Value Decomposition (MTM-SVD), a frequency-domain analysis method, is applied to isolate significant spatially-coherent variability with narrowband oscillatory character. A quasibiennial oscillation is detected as the most intense coherent signal in the stratosphere, the signal being less intense in the lower levels. There is a clear downward propagation of the signal with time at low latitudes, not evident at mid and high latitudes. There are differences in the behavior of the signal over both hemispheres, being much weaker over the SH. In the NH an anomaly in the zonal wind field, in phase with the equatorial signal, is detected at approximately 60degreesN. Two different areas at subtropical latitudes are detected to be characterized by wind anomalies opposed to that of the equator., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

©2001 American Meteorological Society. The authors wish to thank Mr. Cruz Apestegui for advice on the design and sailing characteristics of the Manila galleons, and Drs. A. K. Smith, W. Randel, P. Gent, and A. Kaplan for their comments on the original manuscript. Valuable comments were also provided by two anonymous reviewers. This work was supported in part by a Small Grant for Exploratory Research from the Earth System History (ESH) Program of the National Science Foundation (NSF); the support and encouragement of former ESH Director Dr. Howard Zimmerman is gratefully acknowledged. The National Center for Atmospheric Research is sponsored by NSF., Historical accounts of the voyages of the Manila galleons derived from the Archivo General de Indias (General Archive of the Indies, Seville, Spain) are used to infer past changes in the atmospheric circulation of the tropical Pacific Ocean. It is shown that the length of the voyage between Acapulco, Mexico, and the Philippine Islands during the period 1590-1750 exhibits large secular trends, such that voyages in the middle of the seventeenth century are some 40% longer than those at the beginning or at the end of the century, and that these trends are unlikely to have been caused by societal or technological factors. Analysis of a series of "virtual voyages," constructed from modem wind data,,indicates that sailing time to the Philippines depended critically on the strength of the trade winds and the position of the western Pacific monsoon trough. These results suggest that the atmospheric circulation of the western Pacific underwent large, multidecadal fluctuations during the seventeenth century., National Science Foundation (NSF), EE.UU., Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© Springer-Verlag 2010. This study received support from MICINN through the TRODIM (CGL2007-65891-C05-05/CLI and CGL2007-65891-C05-02/CLI) projects, from IDL-FCUL through the ENAC (PTDC/AAC-CLI/103567/2008) project and from the EU 6th Framework Program (CIRCE) contract number 036961 (GOCE). We would like to thank J. F. González-Rouco for providing useful comments and suggestions. Two anonymous reviewers contributed to improve the final version of this paper., This paper aims to provide a new blocking definition with applicability to observations and model simulations. An updated review of previous blocking detection indices is provided and some of their implications and caveats discussed. A novel blocking index is proposed by reconciling two traditional approaches based on anomaly and absolute flows. Blocks are considered from a complementary perspective as a signature in the anomalous height field capable of reversing the meridional jet-based height gradient in the total flow. The method succeeds in identifying 2-D persistent anomalies associated to a weather regime in the total flow with blockage of the westerlies. The new index accounts for the duration, intensity, extension, propagation, and spatial structure of a blocking event. In spite of its increased complexity, the detection efficiency of the method is improved without hampering the computational time. Furthermore, some misleading identification problems and artificial assumptions resulting from previous single blocking indices are avoided with the new approach. The characteristics of blocking for 40 years of reanalysis (1950-1989) over the Northern Hemisphere are described from the perspective of the new definition and compared to those resulting from two standard blocking indices and different critical thresholds. As compared to single approaches, the novel index shows a better agreement with reported proxies of blocking activity, namely climatological regions of simultaneous wave amplification and maximum band-pass filtered height standard deviation. An additional asset of the method is its adaptability to different data sets. As critical thresholds are specific of the data set employed, the method is useful for observations and model simulations of different resolutions, temporal lengths and time variant basic states, optimizing its value as a tool for model validation. Special attention has been paid on the devise of an objective scheme easily applicable t, MICINN through the TRODIM, IDL-FCUL through the ENAC, EU 6th Framework Program (CIRCE), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2006 by the American Geophysical Union. This paper has been partially funded by NCAR and MPI, which, additionally, kindly provided the data from the models. Furthermore, we want to thank the National Institute of Meteorology (INM) in Spain and the ECMWF for facilitating the accessto the ERA-40 data., The vertical propagation of the El Nino-Southern Oscillation (ENSO) temperature signal has been analyzed in two general circulation models, the Whole Atmosphere Community Climate Model and the Middle Atmosphere European Center - Hamburg Model, and in the ERA-40 reanalysis data set. Monthly mean data have been used, and composite differences ( El Nino - La Nina) have been computed. Our results show that the ENSO signal propagates into the middle atmosphere by means of planetary Rossby waves. Significant wave-like anomalies are observed up to around 40 km. This propagation is strongly influenced by the zonal mean zonal winds, being most effective in midlatitudes of the Northern Hemisphere because ENSO events tend to peak in northern winter, when stratospheric winds are westerly in the Northern Hemisphere, and allow vertical propagation of Rossby waves. In addition, zonal mean temperature anomalies are observed in the middle atmosphere in the tropics and at polar latitudes of the Northern Hemisphere. These anomalies are the result of changes in the residual mean meridional circulation: Our analysis reveals that during an El Nino event, vertical wave propagation and divergence of Eliassen-Palm flux are enhanced, forcing a stronger residual circulation in the stratosphere, which cools the tropics and warms the higher latitudes. This pattern is highly significant in the models during certain months but much less in the ERA-40 data, where other sources of variability ( in particular the quasi-biennial oscillation) also influence the residual circulation., NCAR, MPI, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2016 IOP Publishing Ltd. We thank the editor for handling this paper and the anonymous reviewers for their constructive feedback. We also gratefully acknowledge Isla Simpson and Minfang Ting for providing the stationary wave model code. This research has been supported by the Supercomputing Centre of Galicia (CESGA) through three ICTS projects and FEDER funds. In addition, computing resources were also provided by the Barcelona Supercomputing Center through three RES activities, and by the EOLO cluster of excellence at Universidad Complutense de Madrid. G Chiodo was partly supported by the Spanish Ministry of Education in the framework of the FPU doctoral fellowship (grant AP2009-0064). This work was supported by the Spanish Ministry of Science and Innovation (MCINN) through the CONSOLIDER (CSD2007-00050-II-PR4/07), MATRES (CGL2012-34221), and ExCirEs (CGL2011-24826) projects, and by the European Commission within the FP7 framework through the StratoClim project (Ref. 603557). JM Vaquero acknowledges the support from the Junta de Extremadura (Research Group Grants GR10131) and from the Spanish Government (AYA2011-25945 and AYA2014-57556-P). The authors also aknowledge the COST Action ES1005 TOSCA (http://tosca-cost.eu) and the WCRP/SPARC SOLARIS-HEPPA project (http://solarisheppa.geomar.de/)., Solar variability represents a source of uncertainty in the future forcings used in climate model simulations. Current knowledge indicates that a descent of solar activity into an extended minimum state is a possible scenario. With aid of experiments from a state-of-the-art Earth system model, we investigate the impact of a future solar minimum on Northern Hemisphere climate change projections. This scenario is constructed from recent 11 year solar-cycle minima of the solar spectral irradiance, and is therefore more conservative than the 'grand' minima employed in some previous modeling studies. Despite the small reduction in total solar irradiance (0.36 W m^-2), relatively large responses emerge in the winter Northern Hemisphere, with a reduction in regional-scale projected warming by up to 40%. To identify the origin of the enhanced regional signals, we assess the role of the different mechanisms by performing additional experiments forced only by irradiance changes at different wavelengths of the solar spectrum. We find that a reduction in visible irradiance drives changes in the stationary wave pattern of the North Pacific and sea-ice cover. A decrease in UV irradiance leads to smaller surface signals, although its regional effects are not negligible. These results point to a distinct but additive role of UV and visible irradiance in the Earth's climate, and stress the need to account for solar forcing as a source of uncertainty in regional scale projections., Unión Europea. FP7, Ministerio de Economía y Competitividad (MINECO), Ministerio de Ciencia e Innovación (MICINN), Infraestructuras Científicas y Técnicas Singulares (ICTS), MINECO, Fondo Europeo de Desarrollo Regional (FEDER), UE, Junta de Extremadura, Fundación Pública Galega Centro Tecnolóxico de Supercomputación de Galicia (CESGA), 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.

Documentary climate data describe evidence of past climate arising from predominantly written historical documents such as diaries, chronicles, newspapers, or logbooks. Over the past decades, historians and climatologists have generated numerous document-based time series of local and regional climates. However, a global dataset of documentary climate time series has never been compiled, and documentary data are rarely used in large-scale climate reconstructions. Here, we present the first global multi-variable collection of documentary climate records. The dataset DOCU-CLIM comprises 621 time series (both published and hitherto unpublished) providing information on historical variations in temperature, precipitation, and wind regime. The series are evaluated by formulating proxy forward models (i.e., predicting the documentary observations from climate fields) in an overlapping period. Results show strong correlations, particularly for the temperature-sensitive series. Correlations are somewhat lower for precipitation-sensitive series. Overall, we ascribe considerable potential to documentary records as climate data, especially in regions and seasons not well represented by early instrumental data and palaeoclimate proxies.

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

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.

Extreme weather events are expected to increase due to climate change, which could pose an additional burden of morbidity and mortality. In recent decades, drought severity has increased in several regions around the world, affecting health by increasing the risk of water-, food-, and vector-borne diseases, malnutrition, cardiovascular and respiratory illness, mental health disorders, and mortality. Drought frequency and severity are expected to worsen across large regions as a result of a decrease in precipitation and an increase in temperature and atmospheric evaporative demand, posing a pressing challenge for public health. Variation in impacts among countries and communities is due to multiple factors, such as aging, socioeconomic status, access to health care, and gender, affecting population resilience. Integrative proactive action plans focused on risk management are required, and resources should be transferred to developing countries to reduce their vulnerability and risk.