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This work aims at characterizing the exceptional drought that affected Madeira Archipelago (Portugal) during the 2011–2012 hydrological year while including some major impacts but also the main atmospheric circulation mechanism behind the event. Precipitation records from six meteorological stations are used to assess the extreme drought episode by means of a decile classification. The assessment of the drought duration and severity is further corroborated by the Standardized Precipitation Index (SPI) computed for the 3, 6, 12 and 24 months’ time scales which confirmed that the 2012 drought event was one of the events with higher drought intensity at all scales, being classified as extreme at the 6-month time sale (SPI6 Vegetation activity is assessed through anomalies of NDVI (Normalized Difference Vegetation Index), confirming several large sectors of Madeira under vegetative stress. The southern sector of Madeira Island suffered up to seven months (out of nine) of extremely negative anomalies. From an operational point of view, obtained results reveal the ability of the developed methodology to monitor vegetation stress and droughts in Madeira. The extreme dryness of the Island favoured an unusually intense summer fire season of 2012 (between June and September) in Madeira being the year with highest number of fires in the last decade (with robust data). Furthermore, the main fire hotspots of the 2012 fire season are mostly coincident with the areas affected by drought. The large-scale atmospheric circulation responsible for the setting and intensification of the drought is evaluated using reanalysis data. An extensive high pressure anomaly (maximum above 12 hPa in December) persisted over the North Atlantic during the extended winter months (October to April), centred between the Azores Islands and the UK. This feature is in agreement with a positive NAO index (2.25 in December), a negative EA index (−1.76 in January and −1.73 in February) and compatible with enhanced north-easterly trade winds over the region. As a consequence of this uncharacteristic dynamics there was a deficit of moisture availability over the region as evaluated by the vertically integrated horizontal water vapour transport with a negative anomaly up to −120 kg m−1 s−1.

The summers of 2018 and 2019 were characterized by unusually warm conditions over Europe. Here, we describe the intense heatwaves striking the Iberian Peninsula in early August 2018 and late June 2019. The 2018 episode was relatively short-lived but outstanding in amplitude, particularly in western Iberia. Similar to previous mega-heatwaves, the 2019 event was long-lasting and affected large areas of western and central Europe, including eastern Iberia. During these events, many absolute temperature records were broken in western and eastern Iberia, respectively (some of them standing since 2003). In both cases, a cyclonic circulation off the coast in the northeastern Atlantic and a strong subtropical ridge pattern over the affected area promoted the advection of an anomalously warm air mass. This paper highlights the role of these very warm, stable and dry air intrusions of Saharan origin in the western and eastern Iberia heatwave events. Using a thermodynamical classification based on the geopotential height thickness and potential temperature, we show how the magnitude and poleward extension of these Saharan intrusions were unprecedented in the period since 1948. The relationship between Iberian heatwaves and Saharan warm air intrusions is discussed in the long-term context, showing a closer link in southern sectors of the Peninsula. However, a consistent poleward trend in the latitudinal extension of these subtropical intrusions reveals their increasing relevance for heatwaves in northern sectors of Iberia and western Europe. This overall trend is accompanied by an apparent “see-saw” in the occurrence of subtropical intrusions between eastern and western Iberia on multi-decadal scales., We acknowledge the E-OBS dataset from the EU-FP6 project ENSEMBLES (http://ensembleseu.metoffice.com) and the data providers in the ECA&D project (http://www.ecad.eu). PMS was supported by the projects IMDROFLOOD – Improving Drought and Flood Early Warning, Forecasting and Mitigation using real-time hydroclimatic indicators (WaterJPI/0004/2014) and HOLMDRIVE – North Atlantic Atmospheric Patterns influence on Western Iberia Climate: From the Lateglacial to the Present [PTDC/CTA-GEO/29029/2017] through Fundação para a Ciência e a Tecnologia, Portugal (FCT). RMT was partially supported by national funds through Fundação para a Ciência e a Tecnologia, Portugal (FCT) under project FireCast (PCIF/GRF/0204/2017). This research was partially funded by the European Union’s Horizon 2020 research and innovation programme under Grant agreement No 690462 within the frame of the ERANET “European Research Area for Climate Services –ERA4CS” 2016 Call. AMR was supported by the Scientific Employment Stimulus 2017 from FCT (CEECIND/00027/2017). We thank the Editor and reviewers for their helpful comments on this manuscript.

The present work presents a new observational gridded dataset (referred to as Iberia01) for daily precipitation and temperatures produced using a dense network (thousands) of stations over the Iberian Peninsula for the period 1971-2015 at 0.1° regular (and 0.11° CORDEX-compliant rotated) resolutions. We analyze mean and extreme indices and compare the results with the E-OBS v17 dataset (using both the standard and ensemble versions, at 0.25 and 0.1° resolutions, respectively), in order to assess observational uncertainty in this region. We show that Iberia01 produces more realistic precipitation patterns than E-OBS for the mean and extreme indices considered, although both are comparable for temperatures. To assess the differences between these datasets, a new probabilistic intercomparison analysis was performed, using the E-OBS ensemble (v17e) to characterize observational uncertainty and testing whether Iberia01 falls within the observational uncertainty range provided by E-OBS. In general, uncertainty values are large in the whole territory, with the exception of a number of kernels where the uncertainty is small, corresponding to the stations used to build the E-OBS grid. For precipitation, significant differences-at the 10% level-between both datasets were found for fewer than 25% of days over the Iberian Peninsula. For temperature, a very inhomogeneous spatial pattern was obtained, with either a small (in most of the regions) or large fraction of significantly different days, thus indicating sensible regions for observational uncertainty., This research has been partially funded by the Spanish R&D program MINECO/FEDER (grant no. CGL2015-66583-R, project MULTI-SDM), the Portuguese Foundation for Science and Technology – FCT (grant no. PTDC/GEOMET/7078/2014, SOLAR project; grant no. UID/GEO/50019/2019, Instituto Dom Luiz).

Within the scope of the two major international projects of long-term reanalysis for the 20th century coordinated by the National Oceanic and Atmospheric Administration and European Centre for Medium-Range Weather Forecasts, the Instituto Dom Luiz from the University of Lisbon has digitized a large number of long-term daily and monthly climate records from stations in Portugal and former Portuguese colonies. We have recently finished the digitization of precipitation values from Ponta Delgada (capital of the Azores Archipelago), obtaining an almost complete daily precipitation series, with the exception of some years (1864–1872; 1878–1879; 1888–1905; 1931; 1936; and 1938) for which only monthly values are available. At daily resolution, we have used a comprehensive assessment on different characteristics of rain spells (consecutive days with rainfall accumulation). The distribution of precipitation presents an evident seasonal pattern and reveals large inter-annual and intra-annual variability, increasing considerably in the last 3 decades. The frequency of dry years decreases almost by half between the first and the second part of the record, whereas wet years increase up to three times. This is mainly due to more intense events that are reflected by higher rain-spell yields (amount of precipitation) and rain-spell intensity (amount of precipitation per day) values. Most of the extreme precipitation events occurred during the last 2 decades, and they generally correspond to dates with cyclonic conditions over the North Atlantic. We have also looked into the influence of large-scale modes of climate variability on the precipitation regime of the Azores Archipelago. As expected, theNorth Atlantic Oscillation (NAO) has a major impact on the precipitation regime of Ponta Delgada both in winter and summer. However, our results show a non-stationary NAO influence and the impact of other large-scale modes (including the Atlantic Multidecadal Oscillation and El Nino-Southern Oscillation) increases when this influence becomes weaker.

Given the inconsistencies of wind gust trends under the widespread decline in near-surface wind speed (stilling), our study aimed to assess trends of observed daily peak wind gusts (DPWG) across Spain and Portugal for 1961–2014 by analyzing trends of (i) the frequency (90th percentile) and (ii) the magnitude (wind speed maxima) of DPWG. Wind gust series were homogenized on a daily basis, using MM5-simulated series as reference, resulting in 80 suitable station-based data sets. The average DPWG 90th percentile frequency declined by −1.49 d decade−1 (p 0.10). A negligible trend was calculated for the annual magnitude of DPWG (−0.005 m s−1 decade−1; p > 0.10), with distinct seasonality: declining in winter (−0.168 m s−1 decade−1; p 0.10), especially for the frequency, suggesting the role of local-to-mesoscale drivers.

Near-surface wind speed trends recorded at 67 land-based stations across Spain and Portugal for 1961-2011, also focusing on the 1979-2008 subperiod, were analyzed. Wind speed series were subjected to quality control, reconstruction, and homogenization using a novel procedure that incorporated the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5)-simulated series as reference. The resultant series show a slight downward trend for both 1961-2011 (-0.016ms-1 decade-1) and 1979-2008 (-0.010ms-1 decade-1). However, differences between seasons with declining values in winter and spring, and increasing trends in summer and autumn, were observed. Even though wind stilling affected 77.8% of the stations in winter and 66.7% in spring, only roughly 40% of the declining trends were statistically significant at the p < 0.10 level. On the contrary, increasing trends appeared in 51.9% of the stations in summer and 57.4% in autumn, with also around 40% of the positive trends statistically significant at the p < 0.10 level. In this article, the authors also investigated (i) the possible impact of three atmospheric indices on the observed trends and (ii) the role played by the urbanization growth in the observed decline. An accurate homogenization and assessment of the long-term trends of wind speed is crucial for many fields such as wind energy (e.g., power generation) and agriculture-hydrology (e.g., evaporative demand). © 2014 American Meteorological Society., The authors wish to acknowledge the editor and three anonymous reviewers for their detailed and helpful comments to the original manuscript. This research was supported by (i) the JAE-DOC043 (CSIC; European Social Fund, FSE) and the JCI-2011-10263 Grants; (ii) A. S.-L. received a postdoctoral fellowship from the Secretaria per a Universitats i Recerca del Departament d’Economia i Coneixement, de la Generalitat de Catalunya i del programa Cofund de les Accions Marie Curie del 7è Programa marc d’R+D de la Unió Europea (2011 BP-B 00078); (iii) Projects CGL2011-27574-C02-02, CGL2011-27536/HID, CGL2011-29263-C02-01, and PSE.120000.2007.14, financed by the Spanish Commission of Science and Technology and FEDER; ACQWA (FP7-ENV- 2008-1-212250), financed by the European Comission; Efecto de los escenarios de cambio climático sobre la hidrología superficial y la gestión de embalses del Pirineo Aragonés, financed by Obra Social La Caixa; CTTP1/12 Creación de un modelo de alta resolución espacial para cuantificar la esquiabilidad y la afluencia turística en el Pirineo bajo distintos escenarios de cambio climático, financed by the Comunidad de Trabajo de los Pirineos; ENAC (PTDC/AAC-CLI/103567/2008), financed by the Portuguese Science Foundation; and (iv) the Climatology Group (2009 SGR 443, Catalan Government). The authors thank the AEMET and the IPMA institutions for the observed wind data and particularly José-Antonio Guijarro (AEMET-Baleares) and Juan-José Vizcaíno (AEMET-Valencia) for their useful comments and information. We thank Ptr Stepanek for providing the AnClim software and the MAR research group of the University of Murcia for providing the MM5-simulated wind speed series, particularly the assistance of Raquel Lorente-Plazas and Juan Pedro Montávez.

Precipitation extremes in mainland Portugal (south-western Europe) using daily precipitation data recorded in the period 1941–2007 (67 years) at 57 meteorological stations scattered across the area are studied at an annual scale. Trends in selected precipitation annual indices that are calculated from these data are investigated, in particular trends in the intensity, frequency and duration of extreme precipitation events. Special attention is dedicated to local and regional variability. The spatial correlations between the annual trends in mean precipitation and in the extremes are analysed. Moreover, the relationships between the variability of the North Atlantic Oscillation (NAO) index and several indices related to the frequency and intensity of the precipitation at the 57 stations were also investigated. Results show that several stations have predominantly negative tendencies in the precipitation indices, although the majority of stations did not show statistically significant change over time in the 1941–2007 period. At the regional level, the decreasing trend in the simple daily precipitation intensity index is the only one statistically significant at the 5 % level and appears to be related to the predominance of the positive phase of the NAO. For the period 1976–2007, the proportion of the total precipitation attributed to heavy and very heavy precipitation events increased and, consequently, daily precipitation events show a tendency to become more intense. Moreover, correlation analysis show that the most extreme events could be changing at a faster absolute rate in relation to the mean than more moderate events.

This study aims mostly at understanding seasonal variations in the intensity, frequency and duration of extreme precipitation events in mainland Portugal. For this purpose, selected precipitation indices that mainly focus on extremes were calculated at the seasonal scale for daily data recorded in the period 1941–2007 at 57 meteorological stations scattered across the area. These indices were explored for trends at the local and regional levels. The results show that there are marked changes in precipitation indices at the seasonal scale. Trends in spring and autumn precipitation have opposite signals. In spring, statistically significant drying trends are found together with a reduction in extremes. In autumn, wetting trends are detected for all indices, although overall they are not significant at the 5 % level. In addition, the relationship between seasonal extreme precipitation indices and atmospheric large-scale modes of low-frequency variability is analysed by means of a seasonal correlation analysis. Four modes of low-frequency variability are explored. Results confirm that, over mainland Portugal, the North Atlantic Oscillation is one of the most important teleconnection patterns in any season and the mode of variability that has the greatest influence on precipitation extremes in the area, particularly in the winter and autumn.

This study provides a thorough assessment of recent changes in near-surface air temperature in mainland Portugal at both the local and regional level, focusing on extreme events (maximum and minimum) at a seasonal scale. It examines trends in selected specific indices that are calculated from daily air temperature data from 23 measuring stations scattered across the territory, recorded between 1941 and 2006. The results show overall warming trends over mainland Portugal that are consistent with the dominant global warming and reflect an increase in both maximum and minimum air temperature. When we split the study period into two sub-periods, 1945–1975 and 1976–2006, the partial trend analysis reveals that the first sub-period is mostly characterized by cooling followed by an even stronger tendency towards warmer benchmarks in all the indices evaluated, in particular for the warm-related temperature extremes in spring and summer. The changes observed in seasonal patterns confirm the well-known asymmetries in the climate in mainland Portugal and suggest that they are likely to be aggravated. There are changes associated with extreme temperatures, in particular, the significant increase in the frequency and duration of heat waves, and the increase in the frequency of hot days and tropical nights, especially in spring and summer; moreover there is a significant decrease in the frequency of cold waves and frost days. Teleconnections associated with changing patterns of temperature are also investigated. The results show that, over mainland Portugal, cold-related air temperature extremes have been associated with the East Atlantic mode in autumn, whereas warm-related extremes have been associated with the Scandinavia teleconnection pattern in spring, summer and autumn. However, the most prominent Northern Hemisphere pattern, the North Atlantic Oscillation, exerts limited influence, which is felt mostly in winter and spring.

Changes in the climatology of precipitation and surface air temperature are being investigated worldwide, searching for changes in variability, the mean and extreme events (maximum and minimum). By exploring recent adjustments in the climate of mainland Portugal, particularly in the intensity, frequency and duration of extreme events, this study investigates trends in selected specific indices that are calculated from daily precipitation data from 57 and surface air temperature data from 23 measuring stations scattered across the territory. Special attention is paid to regional differences and variations in seasonality. The data cover the periods 1941–2007 for precipitation, and 1941–2006 for temperature. They are explored at the annual and seasonal scales and for different sub-periods. Results show that trends in annual precipitation indices are generally weak and, overall, not statistically significant at the 5% level. Nevertheless, a decreasing trend is revealed by regional indices of total wet-day precipitation and extreme precipitation (above the 99th percentile). Seasonal precipitation exhibits significant decreasing trends in spring precipitation, while extreme heavy precipitation events, in terms of both magnitude and frequency, have become more pronounced in autumn. Results for winter and summer suggest that the extremes have not suffered any significant aggravation. Trends for air temperature are statistically more significant and marked than for precipitation and indicate general warming across the territory. This warming trend is revealed very consistently by the time series of individual stations and regional mean temperature, and is also consistent with the findings reported in other studies for Portugal and at the European scale.

Ponencia presentada en: X Congreso de la Asociación Española de Climatología celebrado en Alicante entre el 5 y el 8 de octubre de 2016. [ES]Dadas las inconsistencias en las tendencias de las rachas máximas diarias de velocidad del viento (DPWG) bajo un escenario de “stilling” (descenso de la velocidad media del viento), este estudio evalúa las tendencias de dos parámetros de las DPWG en España y Portugal durante 1961-2014: (i) la frecuencia (percentil 90); y (ii) la magnitud (velocidad máxima del viento). Las 80 series observadas de las DPWG fueron homogeneizadas a resolución diaria utilizando series de referencia obtenidas a partir del modelo MM5. A escala anual, la frecuencia media de las DPWG mayores que su percentil 90 disminuyó en -1.49 días década-1 (p0.10). A su vez, la tendencia en la magnitud de las DPWG a escala anual no resultó significativa (-0.005 m s-1 década-1; p>0.10), pero sí estacionalmente: descenso en invierno (-0.168 m s-1 década-1; p0.10). A negligible trend was calculated for the annual magnitude of DPWG (-0.005 m s-1 decade-1; p>0.10), with distinct seasonality: declining in winter (-0.168 m s-1 decade-1; p

This study proposes a dynamically downscaled climatology of Portugal, produced by a high resolution (9 km) WRF simulation, forced by 20 years of ERA-Interim reanalysis (1989–2008), nested in an intermediate domain with 27 km of resolution. The Portuguese mainland is characterized by large precipitation gradients, with observed mean annual precipitation ranging from about 400 to over 2,200 mm, with a very wet northwest and rather dry southeast, largely explained by orographic processes. Model results are compared with all available stations with continuous records, comprising daily information in 32 stations for temperature and 308 for precipitation, through the computation of mean climatologies, standard statistical errors on daily to seasonally timescales, and distributions of extreme events. Results show that WRF at 9 km outperforms ERA-Interim in all analyzed variables, with good results in the representation of the annual cycles in each region. The biases of minimum and maximum temperature are reduced, with improvement of the description of temperature variability at the extreme range of its distribution. The largest gain of the high resolution simulations is visible in the rainiest regions of Portugal, where orographic enhancement is crucial. These improvements are striking in the high ranking percentiles in all seasons, describing extreme precipitation events. WRF results at 9 km compare favorably with published results supporting its use as a high-resolution regional climate model. This higher resolution allows a better representation of extreme events that are of major importance to develop mitigation/adaptation strategies by policy makers and downstream users of regional climate models in applications such as flash floods or heat waves.

Changes in surface air temperature extremes over mainland Portugal since the early 1940s were investigated on the basis of daily maximum and minimum temperatures available from time series from 23 weather stations. The maximum (minimum) temperature decreased by 0.17°C decade -1 (0.19°C decade -1 ) for 1941-1975 followed by an increase of 0.49°C decade -1 (0.54°C decade -1 ) for 1976-2006, significantly higher than similar trends computed at the global and Euro- pean scales. A large set of climatic indices was analysed to detect the presence of trends and quan- tify the variations of different indices for different periods. In the 1976-2006 period, many stations revealed statistically significant positive trends in the annual number of tropical nights, summer days, warm spells, warm nights and warm days. At the seasonal level, we detected statistically significant increments of extreme heat events for spring and summer, and a decrease of cold extremes in winter. We then used the HadRM3 output to study changes in the maximum and minimum temperature dis- tributions and associated changes in the likelihood of extreme events in the future (2071-2100) under 2 change scenarios. Changes obtained for the future are consistent with those found since the mid- 1970s in Portugal with an increase in maximum temperature of 3.2°C (4.7°C) for the B2 (A2) scenario in summer and ~3.4°C in both scenarios for spring. For minimum temperature, the results were simi- lar, with increases for summer (spring) ranging from 2.7°C (2.5°C) in the B2 scenario to 4.1°C (2.9°C) in the A2 scenario.

A phenotypic characterization of seventeen Bacillus strains isolated from aerobic thermophilic bioreactors of a food waste processing company was carried out, using fatty acid and enzymatic activity profiles. It was observed that each species possessed a typical fatty acid and enzymatic production profile. Bacillus licheniformis strains exhibited the most significant enzyme production. Numerical analyses (principal component and hierarchical cluster analyses) revealed that Bacillus licheniformis strains were homogeneous regarding their fatty acid profiles whilst B. subtilis and Bacillus pumilus strains showed some phenotypic differences. However, enzymatic activities numerical analyses indicated that these three Bacillus species were more homogeneous regarding this phenotypic characteristic.

The summer of 2003 was characterised by exceptional warm weather in Europe, particularly during the first two weeks of August, when a devastating sequence of large fires was observed, reaching an amount of circa 450 000 ha, the largest figure ever recorded in Portugal in modern times. They were concentrated in two relatively confined regions of Portugal and a considerable proportion of burnt area was due to fires started on the 2nd and 3rd of August. It is shown that the 850 hPa temperature values observed over Portugal for the 1st and 2nd of August 2003 were the highest recorded since 1958. Using data from synoptic stations covering the entire Portuguese territory, the event was characterised in fine detail, including the evolution of both maximum and minimum temperatures, surface relative humidity, and wind anomaly fields. The different spatial extent of maximum and minimum temperatures is analysed leading to the new all-time Portuguese records of 47.3 °C for maximum and 30.6 °C for minimum temperatures that were recorded on the 1st of August near the main area of occurrence of the largest fire. Finally, it is shown that the summer of 2003 was preceded by a wet winter followed by a very dry month of May, a precipitation anomalous regime that contributed to a climatic background that favoured the role played by the early August heatwave and the associated meteorological surface conditions. Copyright © 2006 Royal Meteorological Society

Since 1974, there has been a significant increasing trend in land and sea surface temperatures of 0.5 and 0.24 degrees C decade(-1), respectively, in the NW Iberian Peninsula. Over the same period, annual precipitation does not show any trend, although some tendencies have been detected at seasonal scales. A significant positive trend, on average of 2 cm decade(-1), was also observed in sea level rise from 1943 onwards. Ekman transport perpendicular to the coast (upwelling index) showed a decrease from 1975 to 2008 at both annual and seasonal scales. In addition, the flow of the Mino River (the main river in the area) has also decreased at a mean rate of 18 m(3) s(-1) decade(-1) since 1970. At a synoptic scale, winter cyclone frequency and winter and spring blocking activity have decreased since the 1950s, which may partially explain the winter precipitation decline and the winter and spring temperature increases. These changes in synoptic systems are also in agreement with reported trends in the dominant variability modes of atmospheric circulation affecting NW Iberia, particularly a pronounced positive trend in the North Atlantic Oscillation from the 1970s to the 1990s.

This paper analyses the impact of the 2003 European heatwave on excessive human mortality in Portugal, a country that presents a relatively high level of exposure to heatwave events. A total of 2399 excessive deaths are estimated in continental Portugal, which implies an increase of 58% over the expected deaths. When these values are split by gender, it is seen that women increase (79%), was considerably higher than that recorded for men (41%). The increment of mortality due to this heatwave was detected for all the 18 districts of the country, but its magnitude was significantly higher in the inner districts close to the Spanish border. When we split by gender all districts reveal significant mortality increments for women, while the impact in men's excess deaths is not significant over 3 districts. Several temperature derived indices were used and evaluated in their capacity to explain, at the regional level, the excessive mortality (ratio between observed and expected deaths) by gender. It is shown that the best relationship is found for the total exceedance of extreme days, an index combining the length of the heatwave and its intensity. Both variables hold a linear relationship with r = 0.79 for women and a poorer adjustment ( r = 0.50) for men. Additionally, availability of mortality data split by age also allowed obtaining detailed information on the structure of the population in risk, namely by showing that statistically significant increments are concentrated in the last three age classes (45–64, 65–74 and 75 or more). The use of air conditioning systems in some Portuguese hospitals had a major impact on the decrease (up to 40%) in excessive mortality values. A finer approach is relevant for prevention strategies, since it allows to identify better the target population of any preventive strategy regional and national authorities may be interested to implement.