19 Pags.- 11 Figs.- 2 Tabls. © The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License., The analysis of monthly air temperature trends over mainland Spain during1916–2015 shows that warming has not been constant over time nor general-ized among different months; it has not been synchronous for maximum andminimum air temperatures; and it has been heterogeneous in space. Tempera-ture rose during two characteristic pulses separated by a pause around themiddle of the 20th century in some months. In other months, only the secondrising period is identified, or no warming can be found. In all months, andboth for maximum and minimum air temperatures, a stagnation of theincreasing trend is observed in the last two decades of the study period. Highspatial variability exists in trend signal and significance, and two contrastingtemporal patterns of advance over the study area are identified for maximumand minimum air temperatures. These patterns can be related to prevalentflow directions and relief disposition with respect to the flows associated withlow-variability meteorological patterns North Atlantic Oscillation (NAO) andWestern Mediterranean Oscillation (WEMO). The results show that warmingis a complex phenomenon at regional and sub-regional scales that can only beanalysed using high-spatial-resolution data and considering global and localfactors., This study was funded by Spanish Government, Ministryof Economy and Competitiveness, CLICES project (CGL2017-83866-C3-1-R, CGL2017-83866-C3-3-R) and Ministry of Science and Innovation, EXE project (PID2020-116860RB-C22); Regional Government of Aragon, Geoenvironmental and Global Climate Change Research Group (E02-17R). Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC)., Peer reviewed

13 Pags.- 6 Figs.- 2 Tabls. © 2023 The Authors., Due to its geographical location in the western Mediterranean region, the Iberian Peninsula involves a challenge for current climatic conditions and future projections. In this study we analysed monthly precipitation trends over mainland Spain from 1916 to 2020 by using the new MOPREDAS_century database. This database combines information from the Spanish Meteorological Agency's archives, as well as data retrieved from Annual Summaries between 1916 and 1950. A combination of both sources produced the largest amount of original information ever collected and researched in mainland Spain between 1916 and 2020., Financial support was provided by Spanish Government, Ministerio de Ciencia y Competitividad-FSE, Projects PID2020-116860RB-C22 and CGL2017-83866-C3-1-R. Regional Government of Aragon, Geoenvironmental and Global Climate Change Research Group, Grant/Award Number: E02-17R., Peer reviewed

16 Pags.- 8 Figs.- 3 Tabls. The data that support the findings of this study are openly available in https://digital.csic.es/handle/10261/341441?mode=full at http://hdl.handle.net/10261/341441. This is an open access article under the terms of the Creative Commons Attribution License., This study examines the spatial and temporal variations in seasonal precipitation patterns across the Spanish mainland, within the western Mediterranean Basin, spanning the years 1916–2015. Utilizing the recently developed MOPREDAS_century database at a 10 × 10 km grid resolution, our analysis reveals predominantly negative trends in precipitation across the study area over the entire period, primarily driven by declines in spring precipitation, with lesser decreases in summer and winter. Notably, these trends exhibit complexity, manifesting as two distinct pulses occurring roughly at the outset and conclusion of the 20th century. However, upon employing a moving windows analysis, we find that since the mid-1970s, seasonal precipitation trends have largely been nonsignificant. Spatially, the precipitation regime across 1916–2015 delineates three primary zones: a winter-maximum zone in the north, an autumn-maximum zone along the eastern coast, and a transition from winter-maximum to spring-maximum towards the western and inland regions. Noteworthy shifts in this spatial distribution are evident over the four 25-year intervals examined. Initially, during 1916–1940, winter, autumn and spring regimes occupied 44.1%, 24.2% and 31.7% of the land, respectively. Subsequently, in the periods 1941–1965 and 1966–1990, winter dominance expanded to over 50% of the grid area, while spring varied between 34.7% and 25.5%, and autumn decreased notably to 12.4% and 13.5%. Lastly, significant alterations occurred in the final period of 1991–2015, with winter coverage decreasing to 33.7%, spring to 15.8% and autumn expanding to 50.1% of the grid area. In summary, the prevalent winter and spring regimes at the dawn of the 20th century have transitioned towards an autumn-dominated regime, particularly in much of the central and western Spanish mainland, with these shifts possibly linked to the evolving precipitation trends. These findings contribute novel insights, particularly pre-1950, and align with published results post-1950 across the Mediterranean, particularly in its western regions. Furthermore, they suggest a potential connection between changes in the spatial distribution of seasonal precipitation regimes and temporal variations in the primary moisture sources over the study area., Financial support was provided by Regional Government of Aragon, Geoenvironmental and Global Climate Change Research Group, Grant/Award Number: E02-17R; Spanish Government, Ministerio de Ciencia e Innovación-FSE, Projects: PID2020-116860RB-C22 (AEI/10.13039/501100011033), CGL2017-83866-C3-1-R., Peer reviewed

13 Pags.- 7 Figs.- 1 Tabl. Data availability: All data generated and evaluated in this publication are available at DIGITAL.CSIC repository (https://doi.org/10.20350/digitalCSIC/15446). Code availability: Code used in the 40 drought events characterization is available at DIGITAL.CSIC (https://doi.org/10.20350/digitalCSIC/15446).
© The Author(s) 2024. This article is licensed under a Creative Commons Attribution 4.0 International License., We leveraged the most extensive and detailed gridded database of monthly precipitation data across the Spanish mainland (MOPREDAScentury), encompassing 1916–2020 time period, to pinpoint the most severe drought events within this timeframe and analyse their spatio-temporal dynamics. To identify these events, we employed the Standardized Precipitation Index (SPI) at a 12-month timescale. Drought events were identified as periods of at least three months where significantly dry conditions affected 20% or more of the study area, defined as grid cells with SPI values lower than −0.84. Our analysis revealed a total of 40 major drought events. Our catalogue contains detailed information on each episode’s spatial extent, duration, severity, and spatio-temporal dynamics. The analysis of the propagation patterns of the events unveils substantial heterogeneity, implying that droughts stem from diverse atmospheric mechanisms, further influenced by complex local topography. The open-licensed drought database serves as a valuable resource. It not only facilitates exploration of drought onset and evolution mechanisms but also aids in assessing drought impact on agricultural and other socio-economic sectors., This research has been supported by research grants PID2020-116860RB-C22, CGL2017-83866-C1-3-R, and CGL2017-83866-C3-3-R by the Spanish Ministry of Science and Innovation and by the European Commission – NextGenerationEU (Regulation EU 2020/2094), through CSIC’s Interdisciplinary Thematic Platform Clima (PTI Clima)/Development of Operational Climate Services. We acknowledge support of the Aragón regional Government through grant “E02_23R: Procesos geoambientales y Cambio Global”., Peer reviewed

Flash droughts (FDs) are distinguished by a rapid development associated with strong precipitation deficits and/or increases in atmospheric evaporative demand in the short-term, but little is known about the atmospheric conditions underlying these events. In this study, we analyse for the first time the atmospheric dynamics involved in the development of FDs in Spain over the period 1961–2018. FDs are related to large-scale atmospheric circulation patterns affecting the region, in particular with the positive phase of the North Atlantic Oscillation (NAO). The NAO is the main atmospheric driver of FDs in winter and autumn, and it is essential in explaining FD development in spring. We also found that FDs are typically linked to strong positive anomalies in 500 hPa geopotential height and sea level pressure over the region during the weeks prior to the onset. At the synoptic scale, the most common weather types (WTs) recorded during the development of FDs are Anticyclonic Western (ANT_W_AD), East (E_AD) and Northeast (NE_AD) advection, and Anticyclonic (ANTICYC). In particular, ANTICYC WT is the main atmospheric driver of FDs in summer. Ridging conditions occur frequently during FDs in all seasons, being the most important factor controlling FD development in spring. Likewise, we noted that some of the FDs recorded in summer are related to and/or exacerbated by Saharan air intrusions associated with pronounced ridges. The results of this research have important implications for the understanding, monitoring and prediction of FDs in Spain, providing a detailed assessment of the main atmospheric dynamics involved in FD triggering at different spatial scales., This work has been supported by the research projects: TED2021-129152B-C41, PID2020-116860RB-C22 and PID2022-218 137244OB-I00 financed by the Spanish Ministry of Science, Innovation and Universities., Peer reviewed

21 Pags.- 10 Figs.- 5 Tabls. Data Availability Statement: The data that support the findings of this study are openly available in DIGITAL CSIC at http://hdl.handle.net/10261/354840. © 2025 The Author(s). International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License., Catalogues of past hazardous events are essential for understanding their magnitude, frequency, geographical distribution and underlying mechanisms. Such compilations provide critical data for identifying patterns, improving predictive models, and enhancing preparedness, thereby contributing to the mitigation of future risks and facilitating effective adaptation to climate-related hazards. In this article, we present the first comprehensive catalogue of extraordinary precipitation over the Spanish mainland, spanning more than a century. This work provides valuable insights into spatial and temporal patterns of these events. We compiled monthly maxima of daily precipitation (Rx1day) exceeding 100 and 200 mm by combining the documentary collections of the AEMET National Climate Data Bank (1916–2022) with newly digitised data from the Annual Summaries of Observation Books (1916–1950). As a result, this dataset represents the most extensive and detailed collection of extraordinary precipitation events in the region. It includes 19,184 monthly maxima records above 100 mm from 4325 observatories, occurring across 4814 days (events). Additionally, there are 1130 records exceeding 200 mm, grouped into 530 days and recorded in 664 observatories. As anticipated, extraordinary rainfalls were most frequent in autumn, while summer recorded the lowest number of events. These events occurred across nearly all regions, although a higher concentration were observed near coastlines. This is particularly the case of records and events over 200 mm, which concentrated along the Mediterranean arc. We identified five spatial patterns that correspond with specific weather types. Beyond atmospheric circulation, the topography played a critical role in determining the spatial extension of extraordinary precipitations. The newly digitised dataset is available at https://digital.csic.es/handle/10261/354840, accompanied by a collection of maps of daily events. Raw data from the AEMET's National Climate Data Bank are subject to a licenced agreement., This work was supported by Spanish Governement, Ministerio de Ciencia e Innovación-European Social Fund, Grant/Award Numbers: PID2020-116860RB-C22, CGL2017-83866-C3-1-R; Regional Government of Aragon, Geoenvironmental and Global Climate Change Research Group, Grant/Award Number: E02-23R. Geoenvironmental and Global Climate Change Research Group.”, Peer reviewed

14 Pags.- 9 Figs. Data Availability: Statement Data repository, https://doi.org/10.20350/digitalCSIC/16265 (Beguería and Trullenque-Blanco 2024). © 2025 The Author(s). International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License., Climate aridity (the long-term balance between water availability through precipitation and the atmospheric evaporative de-mand) has a fundamental role in determining water availability and the geographic distribution of ecosystems and agriculturalregions, and plays a crucial role in shaping ecological transitions under current climate change. We computed the Aridity Index,computed as the ratio of precipitation to reference evapotranspiration, over Spain for the period 1961–2020. Here we present spa-tially detailed climatologies of the Aridity Index, at the annual and the monthly scales, and an assessment of changes betweenthe normal periods 1961–1990 and 1991–2020. The results show a transition towards reduced values of the Aridity Index (i.e.,towards drier conditions) at the annual scale, which was more intense in the Canary Islands (where 16.3% of the territory tran-sitioned towards more arid climate categories) than in mainland Spain and the Balearic Islands (11.6%). At the monthly level,the most striking changes over mainland Spain occurred in June, with 39.7% of the territory transitioning towards more aridcategories, while transitions towards more humid conditions have only been relevant in March (23.5%) and October (13.0%) anddid not compensate for the aridification trend when the whole year is considered. In the Canary Islands, the strongest changesoccurred in May (22.6%) and September (19.4%), although drying trends were found almost in all months except the summer., This work has been supported by the Biodiversity Foundation of the Ministry for the Ecological Transition and the Demographic Challenge(MITECO) of the Government of Spain, within the framework of the Recovery, Transformation and Resilience Plan (PRTR), funded by the EuropeanUnion—NextGenerationEU. We also acknowledge financial support from the Ministry of Science, Innovation and Universities of the Government of Spain through research project PID2020-116860RB-C22, and from the Government of Aragón through grant E02-17R., Peer reviewed

Due to its geographical location in the western Mediterranean region, the Iberian Peninsula involves a challenge for current climatic conditions and future projections. In this study we analysed monthly precipitation trends over mainland Spain from 1916 to 2020 by using the new MOPREDAS_century database. This database combines information from the Spanish Meteorological Agency's archives, as well as data retrieved from Annual Summaries between 1916 and 1950. A combination of both sources produced the largest amount of original information ever collected and researched in mainland Spain between 1916 and 2020.

This article describes the development of a monthly precipitation dataset for the Spanish mainland, covering the period between December 1915 and December 2020. The dataset combines ground observational data from the National Climate Data Bank (NCDB) of the Spanish meteorological service (AEMET) and new data rescued from meteorological
yearbooks published prior to 1951 that were never incorporated into the NCDB. The yearbooks' data represented a significant improvement of the dataset, as it almost doubled the number of weather stations available during the first decades of the 20th century, the period when the data were more scarce. The final dataset contains records from
11 312 stations, although the number of stations with data in a given month varies largely between 674 in 1939 and a maximum of 5234 in 1975. Spatial interpolation was used on the resulting dataset to create monthly precipitation grids. The process involved a two-stage process: estimation of the probability of zero precipitation (dry month) and estimation of precipitation magnitude. Interpolation was carried out using universal kriging, using anomalies (ratios with respect to the 1961–2000 monthly climatology) as dependent variables and several geographic variates as independent variables. Cross-validation results showed that the resulting grids are spatially and temporally unbiased, although the mean error and the variance deflation effect are highest during the first decades of the 20th century, when the observational data were more scarce. The dataset is available at https://doi.org/10.20350/digitalCSIC/15136 under an open license and can be cited as Beguería et al. (2023).

This study examines the spatial and temporal variations in seasonal precipitation patterns across the Spanish mainland, within the western Mediterranean Basin, spanning the years 1916–2015. Utilizing the recently developed MOPREDAS_century database at a 10 × 10 km grid resolution, our analysis reveals predominantly negative trends in precipitation across the study area over the entire period, primarily driven by declines in spring precipitation, with lesser decreases in summer and winter. Notably, these trends exhibit complexity, manifesting as two distinct pulses occurring roughly at the outset and conclusion of the 20th century. However, upon employing a moving windows analysis, we find that since the mid‐1970s, seasonal precipitation trends have largely been nonsignificant. Spatially, the precipitation regime across 1916–2015 delineates three primary zones: a winter‐maximum zone in the north, an autumn‐maximum zone along the eastern coast, and a transition from winter‐maximum to spring‐maximum towards the western and inland regions. Noteworthy shifts in this spatial distribution are evident over the four 25‐year intervals examined. Initially, during 1916–1940, winter, autumn and spring regimes occupied 44.1%, 24.2% and 31.7% of the land, respectively. Subsequently, in the periods 1941–1965 and 1966–1990, winter dominance expanded to over 50% of the grid area, while spring varied between 34.7% and 25.5%, and autumn decreased notably to 12.4% and 13.5%. Lastly, significant alterations occurred in the final period of 1991–2015, with winter coverage decreasing to 33.7%, spring to 15.8% and autumn expanding to 50.1% of the grid area. In summary, the prevalent winter and spring regimes at the dawn of the 20th century have transitioned towards an autumn‐dominated regime, particularly in much of the central and western Spanish mainland, with these shifts possibly linked to the evolving precipitation trends. These findings contribute novel insights, particularly pre‐1950, and align with published results post‐1950 across the Mediterranean, particularly in its western regions. Furthermore, they suggest a potential connection between changes in the spatial distribution of seasonal precipitation regimes and temporal variations in the primary moisture sources over the study area.

We leveraged the most extensive and detailed gridded database of monthly precipitation data across the Spanish mainland (MOPREDAScentury), encompassing 1916–2020 time period, to pinpoint the most severe drought events within this timeframe and analyse their spatio-temporal dynamics. To identify these events, we employed the Standardized Precipitation Index (SPI) at a 12-month timescale. Drought events were identified as periods of at least three months where significantly dry conditions affected 20% or more of the study area, defined as grid cells with SPI values lower than −0.84. Our analysis revealed a total of 40 major drought events. Our catalogue contains detailed information on each episode’s spatial extent, duration, severity, and spatio-temporal dynamics. The analysis of the propagation patterns of the events unveils substantial heterogeneity, implying that droughts stem from diverse atmospheric mechanisms, further influenced by complex local topography. The open-licensed drought database serves as a valuable resource. It not only facilitates exploration of drought onset and evolution mechanisms but also aids in assessing drought impact on agricultural and other socio-economic sectors.

Climate aridity (the long‐term balance between water availability through precipitation and the atmospheric evaporative demand) has a fundamental role in determining water availability and the geographic distribution of ecosystems and agricultural regions, and plays a crucial role in shaping ecological transitions under current climate change. We computed the Aridity Index, computed as the ratio of precipitation to reference evapotranspiration, over Spain for the period 1961–2020. Here we present spatially detailed climatologies of the Aridity Index, at the annual and the monthly scales, and an assessment of changes between the normal periods 1961–1990 and 1991–2020. The results show a transition towards reduced values of the Aridity Index (i.e., towards drier conditions) at the annual scale, which was more intense in the Canary Islands (where 16.3% of the territory transitioned towards more arid climate categories) than in mainland Spain and the Balearic Islands (11.6%). At the monthly level, the most striking changes over mainland Spain occurred in June, with 39.7% of the territory transitioning towards more arid categories, while transitions towards more humid conditions have only been relevant in March (23.5%) and October (13.0%) and did not compensate for the aridification trend when the whole year is considered. In the Canary Islands, the strongest changes occurred in May (22.6%) and September (19.4%), although drying trends were found almost in all months except the summer.

ABSTRACTCatalogues of past hazardous events are essential for understanding their magnitude, frequency, geographical distribution and underlying mechanisms. Such compilations provide critical data for identifying patterns, improving predictive models, and enhancing preparedness, thereby contributing to the mitigation of future risks and facilitating effective adaptation to climate‐related hazards. In this article, we present the first comprehensive catalogue of extraordinary precipitation over the Spanish mainland, spanning more than a century. This work provides valuable insights into spatial and temporal patterns of these events. We compiled monthly maxima of daily precipitation (Rx1day) exceeding 100 and 200 mm by combining the documentary collections of the AEMET National Climate Data Bank (1916–2022) with newly digitised data from the Annual Summaries of Observation Books (1916–1950). As a result, this dataset represents the most extensive and detailed collection of extraordinary precipitation events in the region. It includes 19,184 monthly maxima records above 100 mm from 4325 observatories, occurring across 4814 days (events). Additionally, there are 1130 records exceeding 200 mm, grouped into 530 days and recorded in 664 observatories. As anticipated, extraordinary rainfalls were most frequent in autumn, while summer recorded the lowest number of events. These events occurred across nearly all regions, although a higher concentration were observed near coastlines. This is particularly the case of records and events over 200 mm, which concentrated along the Mediterranean arc. We identified five spatial patterns that correspond with specific weather types. Beyond atmospheric circulation, the topography played a critical role in determining the spatial extension of extraordinary precipitations. The newly digitised dataset is available at https://digital.csic.es/handle/10261/354840, accompanied by a collection of maps of daily events. Raw data from the AEMET's National Climate Data Bank are subject to a licenced agreement.

The analysis of temporal changes in extreme event attributes, specifically magnitude and frequency, is hindered by the rarity and exceptional nature of the events being studied. The non-stationary extreme value theory (NSEVT) provides a well-established framework for assessing how extreme event probabilities vary as a function of one or more covariates. This study employs NSEVT to investigate the recent evolution and primary drivers of extreme precipitation in Spain, utilizing indices of three large-scale modes of atmospheric circulation and time as covariates. A non-stationary peaks-over-threshold model is applied to an observational network comprising 341 weather stations over the period 1951–2020. The results demonstrate that a multivariate model accounting for the influences of all covariates fits the data significantly better than simpler, univariate and stationary models in the majority of stations. The multivariate model effectively captures the spatial and temporal marginal influences of atmospheric dynamics on the magnitude-frequency relationship of different attributes of extreme precipitation events, including daily peak intensity and accumulated event precipitation. In contrast, the marginal influence of time is relatively small and sparse, lacking a spatially coherent pattern. Notably, the multivariate model reveals larger temporal influences than those inferred from the univariate model, with more stations displaying significant decreases than increases in extreme precipitation event attributes. These findings highlight the importance of considering multiple covariates and non-stationarity when analyzing temporal changes in extreme events.