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In this study, we identified the moisture sources for the precipitation associated with tropical cyclones (TCs) during the rapid intensification (RI) process from 1980 to 2018 by applying a Lagrangian moisture source diagnostic method. We detected sixteen regions on a global scale for RI events distributed as follows: four in the North Atlantic (NATL), two in the Central and East Pacific Ocean (NEPAC), the North Indian Ocean (NIO) and South Indian Ocean (SIO), and three in the South Pacific Ocean (SPO) and the Western North Pacific Ocean (WNP). The moisture uptake (MU) mostly was from the regions where TCs underwent RI. The Western NATL, tropical NATL, Caribbean Sea, the Gulf of Mexico and the Central America and Mexico landmass supported ∼85.4% of the precipitating moisture in the NATL, while the latter source and the eastern North Pacific Ocean provided the higher amount of moisture in NEPAC (∼84.3%). The Arabian Sea, the Bay of Bengal and the Indian Peninsula were the major moisture sources in NIO, contributing approximately 81.3%. The eastern and western parts of the Indian Ocean supplied most of the atmospheric humidity in SIO (∼83.8%). The combined contributions (∼87.9%) from the western and central SPO and the Coral Sea were notably higher in SPO. Meanwhile, TCs in the WNP basin mostly received moisture from the western North Pacific Ocean, the Philippine Sea and the China Sea, accounting for 80.1%. The remaining moisture support in each basin came from the summed contributions of the remote sources. Overall, RI TCs gained more moisture up to 2500 km from the cyclone centre than those slow intensification (SI) and the total MU was approximately three times higher during RI than SI. Finally, the patterns of the MU differences respond to the typical pathways of moisture transport in each basin.

Abstract We assembled the first gridded burned area (BA) database of national wildfire data (ONFIRE), a comprehensive and integrated resource for researchers, non-government organisations, and government agencies analysing wildfires in various regions of the Earth. We extracted and harmonised records from different regions and sources using open and reproducible methods, providing data in a common framework for the whole period available (starting from 1950 in Australia, 1959 in Canada, 1985 in Chile, 1980 in Europe, and 1984 in the United States) up to 2021 on a common 1° × 1° grid. The data originate from national agencies (often, ground mapping), thus representing the best local expert knowledge. Key opportunities and limits in using this dataset are discussed as well as possible future expansions of this open-source approach that should be explored. This dataset complements existing gridded BA data based on remote sensing and offers a valuable opportunity to better understand and assess fire regime changes, and their drivers, in these regions. The ONFIRE database can be freely accessed at https://zenodo.org/record/8289245 .

Abstract Better understanding how fires respond to climate variability is an issue of current interest in light of ongoing climate change. However, evaluating the global‐scale temporal variability of fires in response to climate presents a challenge due to the intricate processes at play and the limitation of fire data. Here, we investigate the links between year‐to‐year variability of burned area (BA) and climate using BA data, the Fire Weather Index (FWI), and the Standardized Precipitation Evapotranspiration Index (SPEI) from 2001 to 2021 at ecoregion scales. Our results reveal complex spatial patterns in the dependence of BA variability on antecedent and concurrent weather conditions, highlighting where BA is mostly influenced by either FWI or SPEI and where the combined effect of both indicators must be considered. Our findings indicate that same‐season weather conditions have a more pronounced relationship with BA across various ecoregions, particularly in climatologically wetter areas. Additionally, we note that BA is also significantly associated with periods of antecedent wetness and coolness, with this association being especially evident in more arid ecoregions. About 60% of the interannual variations in BA can be explained by climatic variability in a large fraction (∼77%) of the world's burnable regions.

Abstract The western Mediterranean region experienced an exceptional and unprecedented early heatwave in April 2023. By shattering historical temperature records, especially in the Iberian Peninsula and northwestern Africa, this extreme offers a stark illustration of a drought–heatwave compound event. Here, we investigate the soil moisture–temperature interactions that underpinned this event, using the most up-to-date observations and a robust statistical analysis. Our results reveal that soil moisture deficit preconditions, concurring with a strong subtropical ridge as a synoptic driver, had a key contribution to the amplification and duration of this record-breaking heatwave. Specifically, we estimate that the most extreme temperature records would have been 4.53 times less likely and 2.19 °C lower had the soils been wet. These findings indicate that soil moisture content may be a crucial variable for seasonal forecasting of early HW in this region and in other Mediterranean climate regimes that are already suffering an increment in the frequency of compound drought–heatwave events.

Abstract Tropical cyclones (TCs) require substantial amounts of moisture for their genesis and development, acting as important moisture drivers from the ocean to land and from tropical to subtropical and extratropical regions. Quantifying anomalous moisture transport related to TCs is crucial for understanding long-term TC-induced changes in the global hydrological cycle. Our results highlight that, in terms of the global water budget, TCs enhance moisture transport from evaporative regions and precipitation over sink regions, leading to predominantly anomalous positive surface freshwater flux areas over the tropics and more regionally concentrated negative areas over the Intertropical Convergence Zone. Furthermore, we detected seasonal variability in the impact of TC on the hydrological cycle, which is closely related to the annual and seasonal TC frequency. Our analysis also revealed a global statistically significant drop (~40 mm year−1) in TC-induced surface freshwater fluxes from 1980 to 2018 in response to the increasing sea surface temperature and slightly decrease in global TC frequency and lifetime in the last two decades. These findings have important implications for predicting the impacts of TCs on the hydrological cycle under global warming conditions.

Wildfires are disturbances that occur in ecosystems, both naturally and derived from anthropogenic factors, often caused by extreme meteorological conditions, and have recurrently destructive impacts on forests throughout the world. The complex nature of the interactions between wildfires, their dynamics, and human interference from a climate change perspective has motivated a growing number of researchers to address this topic. The fire weather index (FWI) has been extensively used to analyze the link between meteorological fire danger and its local to regional characteristics contributing to the severity of these events, as well as real-time operational monitoring at national and international levels. Recently, a new improved fire danger index that includes the effect of atmospheric instability has been developed, the so-called FWIe. The presence of instability in the atmosphere may be a boost to more energetic wildfires, such as the June 2017 extreme event in central Portugal, making it an important asset in risk monitoring and management. Here, a comprehensive examination of future fire risk on the Iberian Peninsula was performed. Additionally, a comparative analysis between FWI and FWIe was pursued in the context of climate change. We computed both FWI and FWIe using a multi-model ensemble composed of 13 Euro-CORDEX Regional Climate Model (RCM) simulations forced by different global climate models. The historical period (1971–2000) and three projected periods of 30 years (2011–2040, 2041–2070, and 2071–2 100), under three emission scenarios (RCP2.6, RCP4.5, and RCP8.5) were considered. When assessing modelled FWI and FWIe, results show that summer values tend to substantially increase in the future when assuming the historical period as the benchmark, with an expected extension of the danger period to June and, in a lower magnitude, to September. The north-western region of Iberia, including the north of Portugal and the north-western-to-central Spain are the regions with larger increases in danger in the future, which may be critical since these are the regions with more fire-prone vegetation. This work also points to large differences in fire danger projections among scenarios, calling for a distinct set of adaptation needs that should be timely prepared by stakeholders and authorities.

Abstract In this work, we provide instrumental meteorological data recovered for the Extremadura region (interior SW Iberia), from 1826 to mid‐20th century. Meteorological variables such as air temperature, atmospheric pressure, precipitation, wind direction and humidity, among others, were retrieved. In total, more than 750 000 instrumental data in 157 meteorological series belonging to 131 different locations throughout Extremadura were rescued. It must be noted that daily resolution data constitutes 80% of the database. This great effort of digitization and data collection has been carried out with the aim of contributing to a significant expansion of the length of the databases with meteorological information in this region. Therefore, this database will provide a better understanding of climate variability, trends and extreme events of the Extremadura region.

Abstract Solar and wind power are called to play a main role in the transition toward decarbonized electricity systems. However, their integration in the energy mix is highly compromised due to the intermittency of their production caused by weather and climate variability. To face the challenge, here we present research about actionable strategies for wind and solar photovoltaic facilities deployment that exploit their complementarity in order to minimize the volatility of their combined production while guaranteeing a certain supply. The developed methodology has been implemented in an open‐access step‐wise model called CLIMAX. It first identifies regions with homogeneous temporal variability of the resources, and then determines the optimal shares of each technology over such regions. In the simplistic application performed here, we customize the model to narrow the monthly deviations of the total wind‐plus‐solar electricity production from a given curve (here, the mean annual cycle of the total production) across five European domains. For the current shares of both technologies, the results show that an optimal siting of the power units would reduce the standard deviation of the monthly anomalies of the total wind‐plus‐solar power generation by up to 20% without loss in the mean capacity factor as compared to a baseline scenario with an evenly spatial distribution of the installations. This result further improves (up to 60% in specific regions) if the total shares of each technology are also optimized, thus encouraging the use of CLIMAX for practical guidance of next‐generation renewable energy scenarios.

Regional climate warming amplified the exceptional heatwave on the Antarctic Peninsula observed in February 2020, suggest analyses of atmospheric flow analogs.

Abstract Climate change is expected to have impacts on the balance of global food trade networks and food security. Thus, seasonal forecasts of precipitation and temperature are an essential tool for stakeholders to make timely choices regarding the strategies required to maximize their expected cereal yield outcomes. The availability of state-of-the-art seasonal forecasts such as the European Centre for Medium-Range Weather Forecasts (ECMWF) system 5 (SEAS5) may be an asset to help decision making. However, uncertainties and reduced skill may hamper the use of seasonal forecasts in several applications. Hence, in this work, we aim to understand the added value of such dynamical forecasts when compared to persistent anomalies of climate conditions used to predict the production of wheat and barley yields. With that in mind, empirical models relating annual wheat and barley yields in Spain to monthly values of precipitation and temperature are developed by taking advantage of ECMWF ERA5 reanalysis. Then, dynamical and persistence forecasts are issued at different lead times, and the skill of the subsequent forecasted yield is verified through probabilistic metrics. The results presented in this study demonstrate two different outcomes: (1) wheat and barley yield anomaly forecasts (dynamical and persistent) start to gain skill later in the season (typically from April onwards); and (2) the added value of using the SEAS5 forecast as an alternative to persistence ranges from 6 to 16%, with better results in the southern Spanish regions.

Abstract In this study, we investigated the changes in the origin of moisture for the precipitation associated with tropical cyclones (TCs) after extratropical transition (ET) over the North Atlantic Ocean basin from 1980 to 2018. We analyzed the 24 hr before and after the occurrence of ET events. By applying a TC‐centric methodology we found that the moisture uptake (MU) occurred predominantly in the south and southwest sectors within ∼2,000 km of TC center before ET and from the southwest and west sectors after ET. In addition, the development of the cold front and the warm conveyor belt after ET induces changes in the moisture transport pattern. Overall, the secondary circulation of TCs favored the moisture flux inward for TCs precipitation, while the large‐scale baroclinic environment controlled the MU after ET.

Summary: Portugal is regularly affected by destructive wildfires that have severe social, economic, and ecological impacts. The total burnt area in 2017 (∼540,000 ha) marked the all-time record value since 1980 with a tragic toll of 114 fatalities that occurred in June and October events. The local insurance sector declared it was the costliest natural disaster in Portugal with payouts exceeding USD295 million. Here, the 2017 October event, responsible for more than 200,000 ha of burnt area and 50 fatalities is analyzed from a compound perspective. A prolonged drought led to preconditioned cumulative hydric stress of vegetation in October 2017. In addition, on 15 October 2017, two other major drivers played a critical role: 1) the passage of hurricane Ophelia off the Coast of Portugal, responsible for exceptional meteorological conditions and 2) the human agent, responsible for an extremely elevated number of negligent ignitions. This disastrous combination of natural and anthropogenic drivers led to the uncontrolled wildfires observed on 15 October.

Early meteorological observations have been found for the period 1788–1813 in a collection of historical documents entitled “Medical and meteorological observation books” (Livros de observações médicas e meteorológicas) that is preserved nowadays in the Municipal Historical Archive of Almada. Almada is a Portuguese city located on the southern bank of the Tagus River, near the mouth of the river, in front of the capital city of Lisbon, which is located on the northern bank. In this work, more than 5000 meteorological readings for the period 1788–1813 have been recovered and analyzed. Daily values have been preserved for the period 1788–1789. However, only monthly values have stood the test of time for the period 1792–1813. The meteorological variables recovered are temperature, pressure, wind direction and the state of the sky. A quality control was carried out to find possible errors, either in the original data or in the digitization process. Unfortunately, there is no information in the metadata about the instruments or the observational methodology. Pressure and temperature data from modern and reanalysis datasets were used as references to study the agreement between these datasets and the Almada dataset. Daily pressure and temperature values from the Almada dataset were used to study, in particular, the meteorological conditions of the winter of 1788/1789 in Almada because this season was one of the coldest in the last 300 years in Central Europe. The complete dataset of early meteorological observations in Almada is freely available to the scientific community.

Marine temperature extremes are anomalous ocean temperature events, often persisting over several weeks or longer, with potential impacts on physical and ecological processes that often encompass socio-economic implications. In recent years, a considerable effort has been directed at the development of metrics allowing an objective characterization of both marine heatwaves (MHWs) and marine cold spells (MCSs). However, the majority of these metrics do not consider explicitly the spatial extent of the events. Here, we rank and evaluate the relative importance of marine temperature extreme events thanks to a metric, called activity, that combines the number of events, duration, intensity and spatial extent. According to this definition, in the Mediterranean basin between 1982 and 2021, summer 2018 experienced slightly more MHW activity than summer 2003, documented as an exceptional extreme event. Besides, MHW activities were higher in the last two decades while winter MCS activities were higher in the 1980s-1990s. The highest MHW activities occurred preferentially in the western Mediterranean while the strongest MCS activities took place preferentially in the eastern Mediterranean. Moreover, the duration, mean intensity, and activity of the three strongest MHWs are twice as high as those of the three strongest MCSs. The long-term tendency of extreme events activity shows an accelerated increase for summer MHWs (about +150°C.days.10⁶km²) and a linear decrease for winter MCSs in the Mediterranean (about -60°C.days.10⁶km²) over the last four decades.

The Fire Weather Index (FWI) is used to assess meteorological fire danger worldwide. It has been argued that it lacks an atmospheric instability term. A new enhanced FWI (FWIe) was recently developed incorporating atmospheric instability in the form of the Continuous Haines Index (CHI). Here, the first climatological and evolution analysis of these indexes was performed using ERA5 data for the 1980–2020 period. There was a prevalence of higher values over central Iberia; these were heavily modulated by the climate types, topography, and land cover. Southwest and east Iberia suffered the greatest decadal increases in all three indexes. Relating both indexes to occurrences detected by satellite, through fire radiative power (FRP), showed that FWIe provided an improved meteorological fire danger assessment in higher-risk conditions. This showed that greater-risk observations were more prone to be affected by atmospheric instability than lower-danger observations. Case studies for the 2017 central Portugal and 2003 and 2018 Monchique wildfires were additionally conducted to verify these conclusions. This work points to the usefulness of FWIe when/where atmospheric instability may play a critical role in the development of wildfires, which may contribute to a more focused deployment of suppression mechanisms by the authorities.

Increasing atmospheric temperatures are expected to have various impacts on the global water cycle. Here, the authors show that there is an intensification of atmospheric rivers, that causes enhanced evapotranspiration and thus atmospheric moisture uptake in many regions of the world.

North Atlantic Tropical Cyclones (TCs) are major atmospheric hazards that can cause large disruptions to coastal and near-coastal societies. Although most studies focus on those areas with highest impact (e.g., Caribbean Islands, the Gulf and western coast of United States), there is an increasing interest in characterizing changes in occurrence and impacts in areas usually less affected by TCs, particularly in the framework of a changing climate. Here we provide a long-term context evaluating changes in the frequency of TC in the Northeast Atlantic (NEA) basin during the 1978–2019 period. In the last decades, scattered information has shown an impact both from TCs and Post-Tropical Cyclones (PTC) in the NEA. We compute several complementary linear trends and show a significant (p ≤ 0.1) increase in the number of stronger storms in the entire North Atlantic basin, and the amount of TCs and PTCs that reach the NEA, in agreement with previous works. A highly significant relation (p ≤ 0.05) is found between the Atlantic Multidecadal Oscillation (AMO) index and TC activity in both the entire North Atlantic and the NEA basin. Sea surface temperature anomaly maps are produced to better encapsulate the annual variability without the multidecadal oscillation effects and, important cold (warm) pools in cyclogenesis and development zones are found in years with low (high) TC activity. It is also found that the sea surface temperature field plays a minor role in the guiding of storms into the NEA sector. Long-term trends as well as high/low seasonal activity analysis suggest that atmospheric circulation (vertical wind shear, lapse rate, mean sea level pressure and upper-level steering) is more relevant than sea surface temperature in the NEA region.

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.

Abstract Summer fires frequently rage across Mediterranean Europe, often intensified by high temperatures and droughts. According to the state-of-the-art regional fire risk projections, in forthcoming decades climate effects are expected to become stronger and possibly overcome fire prevention efforts. However, significant uncertainties exist and the direct effect of climate change in regulating fuel moisture (e.g. warmer conditions increasing fuel dryness) could be counterbalanced by the indirect effects on fuel structure (e.g. warmer conditions limiting fuel amount), affecting the transition between climate-driven and fuel-limited fire regimes as temperatures increase. Here we analyse and model the impact of coincident drought and antecedent wet conditions (proxy for the climatic factor influencing total fuel and fine fuel structure) on the summer Burned Area (BA) across all eco-regions in Mediterranean Europe. This approach allows BA to be linked to the key drivers of fire in the region. We show a statistically significant relationship between fire and same-summer droughts in most regions, while antecedent climate conditions play a relatively minor role, except in few specific eco-regions. The presented models for individual eco-regions provide insights on the impacts of climate variability on BA, and appear to be promising for developing a seasonal forecast system supporting fire management strategies.

Mapping burned areas using satellite imagery has become a subject of extensive research over the past decades. The availability of high-resolution satellite data allows burned area maps to be produced with great detail. However, their increasing spatial resolution is usually not matched by a similar increase in the temporal domain. Moreover, high-resolution data can be a computational challenge. Existing methods usually require downloading and processing massive volumes of data in order to produce the resulting maps. In this work we propose a method to make this procedure fast and yet accurate by leveraging the use of a coarse resolution burned area product, the computation capabilities of Google Earth Engine to pre-process and download Sentinel-2 10-m resolution data, and a deep learning model trained to map the multispectral satellite data into the burned area maps. For a 1500 ha fire our method can generate a 10-m resolution map in about 5 min, using a computer with an 8-core processor and 8 GB of RAM. An analysis of six important case studies located in Portugal, southern France and Greece shows the detailed computation time for each process and how the resulting maps compare to the input satellite data as well as to independent reference maps produced by Copernicus Emergency Management System. We also analyze the feature importance of each input band to the final burned area map, giving further insight about the differences among these events.

Air pollution and hot temperatures present two major health risks, especially for vulnerable groups such as children, the elderly, and people with pre-existing conditions. Episodes of high ozone concentrations and heat waves have been registered throughout Europe and are expected to continue to grow due to climate change. Here, several different heat and ozone wave definitions were applied to characterize the wave-type extremes for two climatically different regions, i.e., Portugal (South Europe) and Bavaria (Central Europe), and their impacts were evaluated considering each type of hazard independently but also when they occur simultaneously. Heat and ozone waves were analyzed with respect to the underlying atmospheric circulation patterns and in terms of their association with human mortality. Heat waves were identified as the most frequent wave type and, despite different climate settings, a comparable exposure to heat and ozone waves was found in Central and South Europe. Waves were associated with in-situ built-up as well as with advection of air masses. However, in Bavaria waves showed the strongest connection with autochthonous weather conditions, while for Portugal, the strongest relationship appeared for eastern and north-eastern inflow. The most severe events, as measured by excess mortality, were always associated to compound heat-ozone waves.

The Mediterranean storm track constitutes a well-defined branch of the North Hemisphere storm track and is characterised by small but intense features and frequent cyclogenesis. The goal of this study is to assess the level of consensus among cyclone detection and tracking methods (CDTMs), to identify robust features and to explore sources of disagreement. A set of 14 CDTMs has been applied for computing the climatology of cyclones crossing the Mediterranean region using the ERA-Interim dataset for the period 1979–2008 as common testbed. Results show large differences in actual cyclone numbers identified by different methods, but a good level of consensus on the interpretation of results regarding location, annual cycle and trends of cyclone tracks. Cyclogenesis areas such as the north-western Mediterranean, North Africa, north shore of the Levantine basin, as well as the seasonality of their maxima are robust features on which methods show a substantial agreement. Differences among methods are greatly reduced if cyclone numbers are transformed to a dimensionless index, which, in spite of disagreement on mean values and interannual variances of cyclone numbers, reveals a consensus on variability, sign and significance of trends. Further, excluding ‘weak’ and ‘slow’ cyclones from the computation of cyclone statistics improves the agreement among CDTMs. Results show significant negative trends of cyclone frequency in spring and positive trends in summer, whose contrasting effects compensate each other at annual scale, so that there is no significant long-term trend in total cyclone numbers in the Mediterranean basin in the 1979–2008 period.

The relationship between terrestrial carbon sinks and atmospheric modes of variability remains uncertain. Here, the authors show that the coupling of the North Atlantic Oscillation and East-Atlantic patterns explains variations in the European CO2sink from 1982 to 2012.

We evaluated the response of vegetation’s photosynthetic activity to drought conditions from 1998 to 2014 over Romania and the Republic of Moldova. The connection between vegetation stress and drought events was assessed by means of a correlation analysis between the monthly Standardized Precipitation Evaporation Index (SPEI), at several time scales, and the Normalized Difference Vegetation Index (NDVI), as well as an assessment of the simultaneous occurrence of extremes in both indices. The analysis of the relationship between drought and vegetation was made for the growing season (from April to October of the entire period), and special attention was devoted to the severe drought event of 2000/2001, considered as the driest since 1961 for the study area. More than three quarters (77%) of the agricultural land exhibits a positive correlation between the two indices. The sensitivity of crop areas to drought is strong, as the impacts were detected from May to October, with a peak in July. On the other hand, forests were found to be less sensitive to drought, as the impacts were limited mostly to July and August. Moreover, vegetation of all land cover classes showed a dependence between the sign of the correlation and the elevation gradient. Roughly 60% (20%) of the study domain shows a concordance of anomalously low vegetation activity with dry conditions of at least 50% (80%) in August. By contrast, a lower value of concordance was observed over the Carpathian Mountains. During the severe drought event of 2000/2001, a decrease in vegetation activity was detected for most of the study area, showing a decrease lasting at least 4 months, between April and October, for more than two thirds (71%) of the study domain.

The Mediterranean region is characterized by the frequent occurrence of summer wildfires, representing an environmental and socioeconomic burden. Some Mediterranean countries (or provinces) are particularly prone to large fires, namely Portugal, Galicia (Spain), Greece, and southern France. Additionally, the Mediterranean basin corresponds to a major hotspot of climate change, and anthropogenic warming is expected to increase the total burned area due to fires in Mediterranean Europe. Here, we propose to classify summer large fires for fifty-four provinces of the Iberian Peninsula according to their local-scale weather conditions and fire danger weather conditions. A composite analysis was used to investigate the impact of local and regional climate drivers at different timescales, and to identify distinct climatologies associated with the occurrence of large fires. Cluster analysis was also used to identify a limited set of fire weather types, each characterized by a combination of meteorological conditions. For each of the provinces, two significant fire weather types were identified—one dominated by high positive temperature anomalies and negative humidity anomalies, and the other by intense zonal wind anomalies with two distinct subtypes in the Iberian Peninsula., allowing for the identification of three distinct regions.

In this work, a landslide event that took place on January 1831 at the Pedregoso Mountains, Cabeza del Buey, SW Spain, is described. This landslide had not been documented to date and was only described in the local press. This event involved an estimated amount of dislodged material in the order of 104 m3. The amount of meteorological data is very scarce as the event occurred before the setting up of the national meteorological service in Spain. However, data from the relatively near location of SW Iberia suggest that the landslide was preceded by a prolonged period of unusually high precipitation totals and that this intense wet period is compatible with the large-scale atmospheric configuration in the winter of 1829–1830. In fact, the North Atlantic Oscillation (NAO) index for that winter achieved one of the most negative values observed in the bicentennial period spanning 1821 to 2019. This multidisciplinary work represents the first attempt to report and describe the main triggering mechanism for an historical landslide in the Extremadura region that is similar to other great historical landslides which have already been documented for other locations in Spain.

This study identifies and characterizes the importance of the Atmospheric Rivers in the extreme precipitation episodes that strike the Iberian Peninsula and Portugal during the extended summer months (April to September) between 1950 and 2007. The extreme precipitation days are ranked taking into account a daily gridded precipitation database for the Iberian Peninsula at a 0.2° resolution. The ranking is based on the magnitude of the extreme precipitation days considering not only on the area affected above the 95th climatological percentile but also by the precipitation intensity within the anomalous area. The Atmospheric Rivers detection scheme is used for the North Atlantic Ocean basin that allows the identification of the persistent Atmospheric Rivers that impact the Iberian Peninsula for the extended summer months. It is shown, that there is a relationship between the Atmospheric Rivers and the extreme precipitation days in Portugal especially during the transition months of April, May and September. On the contrary when analysing the entire Iberia Peninsula the impact of ARs is considerably reduced. Moreover, the impacts of the Atmospheric Rivers is considerably higher for the top ranked events in Portugal but decreases when considering less intense extreme precipitation days.

The European Macaronesia Archipelagos (Azores, Madeira and Canary Islands) are struck frequently by extreme precipitation events. Here we present a comprehensive assessment on the relationship between atmospheric rivers and extreme precipitation events in these three Atlantic Archipelagos. The relationship between the daily precipitation from the various weather stations located in the different Macaronesia islands and the occurrence of atmospheric rivers (obtained from four different reanalyses datasets) are analysed. It is shown that the atmospheric rivers’ influence over extreme precipitation (above the 90th percentile) is higher in the Azores islands when compared to Madeira or Canary Islands. In Azores, for the most extreme precipitation days, the presence of atmospheric rivers is particularly significant (up to 50%), while for Madeira, the importance of the atmospheric rivers is reduced (between 30% and 40%). For the Canary Islands, the occurrence of atmospheric rivers on extreme precipitation is even lower.

The large number of floods and landslides that occurred on 5–16 February 1979 in Portugal was a major hydro-geomorphologic extreme event according to the DISASTER database in terms of number of displaced people. The February 1979 event is the top ranked episode in terms of the total number of evacuated people (4244), displaced people (14,322) and also on the number of days of event duration (12 days) for the period 1865–2015. In this event, 62 damaging floods and five damaging landslides causing eight fatalities were recorded in Portugal. This event was driven by an unusually intense atmospheric forcing mechanism acting at different time scales. Despite the intense magnitude and the widespread impact on the population, this event has not been studied in detail. In this study, we show that the precipitation period of February 1979 had produced several multi-day accumulated precipitation events over the Portuguese continental territory, ranking among the top 10 events observed between 1950–2008. Additionally, most of the precipitation from this event occured in days in which atmospheric circulation was dominated by “wet” circulation weather types (CWTs), namely, cyclonic (C), west (W) or southwest (SW) types.

Drought class transitions over a sector of Eastern Europe were modeled using log-linear models. These drought class transitions were computed from time series of two widely used multiscale drought indices, the Standardized Preipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI), with temporal scales of 6 and 12 months for 15 points selected from a grid over the Prut basin in Romania over a period of 112 years (1902–2014). The modeling also took into account the impact of North Atlantic Oscillation (NAO), exploring the potential influence of this large-scale atmospheric driver on the climate of the Prut region. To assess the probability of transition among different drought classes we computed their odds and the corresponding confidence intervals. To evaluate the predictive capabilities of the modeling, skill scores were computed and used for comparison against benchmark models, namely using persistence forecasts or modeling without the influence of the NAO index. The main results indicate that the log-linear modeling performs consistently better than the persistence forecast, and the highest improvements obtained in the skill scores with the introduction of the NAO predictor in the modeling are obtained when modeling the extended winter months of the SPEI6 and SPI12. The improvements are however not impressive, ranging between 4.7 and 6.8 for the SPEI6 and between 4.1 and 10.1 for the SPI12, in terms of the Heidke skill score.