Are Atmospheric Situations Now More Favourable for Heavy Rainfall in the Spanish Mediterranean? Analysis of Episodes in the Alicante Province (1981–2020)

Intense rainfall (≥100 mm/24 h) constitutes the most frequent atmospheric hazard on Spain’s Mediterranean coast; this phenomenon causes serious damage to property and kills or injures inhabitants. The Intergovernmental Panel on Climate Change, in its latest report in 2022, indicates that in the current climate change scenario, these episodes will become more frequent, hence the importance of analysing and characterising them. The present paper analysed intense rainfall episodes in the central sector of the Spanish Mediterranean coast (province of Alicante) in the 1981–2020 period. A total of 129 episodes were identified which have affected different areas of this province. The rainfall events were analysed by means of three synoptic classification methods subjective/manual and objective/automatic in order to assess the strengths and weaknesses of the two modalities. The main objective was to identify the most favourable atmospheric situations triggering intense rainfall in the study area. The period with the highest propensity for these episodes to develop was identified, as well as the geographical areas most affected in the study period. Autumn concentrates the biggest amount of intense rainfall episodes throughout the year. Herein, we attempt to demonstrate the relationship between atmospheric situation, accumulated rainfall volume, geographical area affected, and the most favourable period of the year for the development of these events. The main results of the synoptic analysis of extreme events show the coincidence, in the three classification methods used, that the existence of instability in the middle and upper layers of the atmosphere (DANA and troughs) and humid and warm E and NE surface flows are decisive. In addition, the warming recorded in the waters of the western Mediterranean in recent decades is related to extreme events.This research was funded by the Vice-Rectorate for Research of the University of Alicante (predoctoral fellowship to E.S.-A., reference FPUA2019-54), the Interuniversity Institute of Geography of the University of Alicante (Research Groups Water and Territory; Climate and Spatial Planning) and Proyecto EXE (PID2020-116860RB-C21) financiado por el Ministerio de Ciencia e Innovación y Fondos FEDER (IP: J.Martin-Vide)

Climatology and ranking of hazardous precipitation events in the western Mediterranean area

The western Mediterranean region often suffers from the devastating effects of flooding, caused by enormous rain accumulations that sometimes resemble the values produced by tropical systems. Despite the climatic and social relevancy of this type of episodes, there are some fundamental questions that would still be difficult to answer today, for example: where within the region are more cases recorded? or, which were the most potentially dangerous episodes? In this study, we identify, and then gather and unify information from, all the daily events occurred from 1980 to 2015. Using the MESCAN high-resolution gridded rainfall dataset, events are detected and for each case, the date and affected regions are recorded. Subsequently, events are ranked according to their magnitude and classified by weather type. In addition, flood data from the FLOODHYMEX and EM-DAT databases are used to check whether the precipitation episodes resulted in flooding. All this information is collected into a publicly available single database. Results show that the highest number of events per year is recorded in the Languedoc-Roussillon region (France) and in the Valencian Community (Spain). The cases of greatest magnitude, which are associated with a larger number of floods, present a very marked seasonality, with about 80% of them occurring in September, October and November. Finally, we show that only four weather types are present in most of the days with hazardous rainfall in the western Mediterranean. The most hazardous situation is characterized by a low-pressure area at all tropospheric levels in the eastern Atlantic, forming a block pattern with an anticyclonic ridge that tends to extend from the Central Mediterranean to Central Europe. About 40% of the most extraordinary cases are associated with this configuration. As an example, the infamous Piedmont (Italy) 1994 episode, in the top 10 of the ranking, was produced by an atmospheric pattern of this typeFunding comes from the Spanish Ministerio de Economia y Competitividad OPERMO (CGL2017-89859-R to GMM and DIC), CLICES (CGL2017-83866-C3-2-R to MLC) and M-CostAdapt (CTM2017-83655-C2-2-R to MCLL) projects, the European Union Interreg V POCTEFA project (EFA210/16 PIRAGUA to MCLL) and the CRETUS strategic partnership (AGRUP2015/02 to GMM and DIC). All these programs are co-funded by the European Union ERDF. DIC and MLC were awarded a pre-doctoral FPI (PRE2018-084425) and FPU (FPU2017/02166) grant, respectively, both from the Spanish Ministry of Science, Innovation and UniversitiesS

Floods in the Pyrenees: a global view through a regional database

This paper shows the first systematic dataset of flood episodes referring to the entire Pyrenees massif, named PIRAGUA_flood, which covers the period 1981–2015 (available at http://hdl.handle.net/10261/270351, last access: 21 July 2024). First, the structure of the database is detailed so that it can be reproduced anywhere else in the world, adapting to the specific nature of each situation. Subsequently, the paper addresses the spatial and temporal distribution of flood episodes and events (including trends) that affected the Pyrenees regions of Spain (Catalonia, Aragon, Navarre, the Basque Country), France (Nouvelle-Aquitaine, Occitanie) and Andorra, as well as the massif as a whole, for a given period of time. In the case of the Spanish regions, it was also possible to analyse the compensation payments by the Spanish Insurance Compensation Consortium and the number of deceased. The weather types associated with flood episodes were also classified based on sea level pressure and 500 hPa geopotential height from ERA5. The results show 181 flood events and 154 fatalities, some of which affected more than one region. In the Spanish part of the Pyrenees, between 1996 and 2015, there was a total compensation payout amounting to EUR 142.5 million (2015). The eastern part of the area records more flood events than the western one, with Catalonia being the community that registered the highest number of events, followed by Andorra and Occitanie. Associated weather types are dominated by the southern component flow over the Pyrenees region, with a talweg on the Iberian Peninsula and a depression in the vicinity, either in the Atlantic or in the Mediterranean. In terms of the entire massif, there is a slight positive trend of 0.84 events per decade, driven by the evolution of ordinary and extraordinary floods but not significant at 95 %. At a regional level, flood behaviour is more heterogeneous, although not significant for the most part. Nouvelle-Aquitaine is the only region that shows a positive and significant trend of 0.34 events per decade.</p

Heat and cold waves in mainland Spain: Origins, characteristics, and trends

Heat and cold waves are extreme temperature events with a high potential of causing negative impacts on human health, and natural and socioeconomic systems, depending on their duration and intensity. There is, however, no consensual approach to address their definition, which is critical to set priority action areas to prevent such risks. Mainland Spain experiences heat and cold waves every year with important impacts especially in the most populated areas with mild or transition climates. Here we used a high-resolution (5 × 5 km) gridded daily temperature dataset and employed a combination of threshold exceedances of maximum and minimum temperature in the same day to identify heat and cold wave events over 75 years (1940–2014). We further examined the duration and the seasonal/annual intensities to detect potential spatial and temporal patterns. Additionally, we used the days within the most widespread events to perform a synoptic classification to categorise the atmospheric conditions leading to high-risk situations. Our results show a similar historical duration of heat and cold waves (4–5 days) and a much higher seasonal intensity of cold ones (double than heat waves). We find a tipping point in the early 1980s from which heat waves became more frequent, longer, and more intense than cold waves. Finally, we discern between 9 historical weather types with a dominance of southern advections driving heat waves and cold continental north-northeast air masses causing cold waves. Understanding the patterns and trends of heat and cold waves, as well as the mechanisms of their genesis is key to assist in risk management in mainland Spain, especially in the context of a warming climate scenario. © 2022 The Author

A component-based approximation for trend detection of intense rainfall in the Spanish Mediterranean coast

Rainfall behavior is a fundamental issue in areas with scarce and irregular amounts, such as the Spanish Mediterranean region. We identified 12 spatial patterns that characterized 899 torrential precipitation events (≥150 mm in 24 h) that occurred in the 3,537 rainy precipitation series in the period 1950–2020. Three of these components––eastern and ESE––showed positive and significant trends in their accumulated volumes. We then characterized the mean synoptic causes of the 10 most intense events in each component at both mean sea-level pressure and 500 hPa geopotential height, and also the integrated water-vapor transport between 1,000 and 300 hPa. We found a clear spatial distribution of the pluviometric effects related to unstable atmospheric situations (such as troughs and cut-off lows), and also to SW–SE advection fluxes that brought moist air from the Western Mediterranean. In particular, torrential rainfall in the Balearic Islands related more to E–NE advections than to southeastern ones. We also determined that the major parts of these components occurred in early autumn, especially in September and October. We expect these findings to help our understanding of the processes leading to catastrophic situations along the Spanish Mediterranean coast and to lead to improvements in early alert systems and management plans.The authors want to thank the Proyecto UTA-Mayor N° 5807–22 from the Universidad de Tarapacá, Chile. MLC, JMV, PS and OMR want to thank the Climatology Group (2017SGR1362, Catalan Government). RSN is partially supported by the Universidad Autónoma de Madrid (UAM) and the Comunidad de Madrid through project SI3-PJI-2021-00398, the Natural Hazards and Global Change research group from UAM, and the Government of Aragón through the “Program of research groups” (group H09_20R, “Climate, Water, Global Change, and Natural Systems”). JJM and MJE participation has been funded by the Spanish Ministerio de Ciencia e Innovación through the research project PID2020-118797RB-I00 (MCIN/AEI/10.13039/501100011033) and by Generalitat Valenciana through the research project PROMETEO/2021/016 (Conselleria d’Innovació, Universitats, Ciència i Societat Digital)

A component-based approximation for trend detection of intense rainfall in the Spanish Mediterranean coast

Rainfall behavior is a fundamental issue in areas with scarce and irregular amounts, such as the Spanish Mediterranean region. We identified 12 spatial patterns that characterized 899 torrential precipitation events (≥150 mm in 24 h) that occurred in the 3,537 rainy precipitation series in the period 1950-2020. Three of these components--eastern and ESE--showed positive and significant trends in their accumulated volumes. We then characterized the mean synoptic causes of the 10 most intense events in each component at both mean sea-level pressure and 500 hPa geopotential height, and also the integrated water-vapor transport between 1,000 and 300 hPa. We found a clear spatial distribution of the pluviometric effects related to unstable atmospheric situations (such as troughs and cut-off lows), and also to SW-SE advection fluxes that brought moist air from the Western Mediterranean. In particular, torrential rainfall in the Balearic Islands related more to E-NE advections than to southeastern ones. We also determined that the major parts of these components occurred in early autumn, especially in September and October. We expect these findings to help our understanding of the processes leading to catastrophic situations along the Spanish Mediterranean coast and to lead to improvements in early alert systems and management plans

Record-shattering 2023 Spring heatwave in western Mediterranean amplified by long-term drought

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 degrees 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

Record-shattering 2023 Spring heatwave in western Mediterranean amplified by long-term drought

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

Daily concentration of snowfalls in the mountains of the Iberian Peninsula

© 2023 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 License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.The temporal concentration of snowfalls has direct implications on the management of water resources as well as on the economic activity of mountain areas, conditioning, for example, the seasonal performance of ski resorts. This work uses the daily concentration index (CI) for analysing the frequency concentration of snowfalls in the Iberian Peninsula Mountain ranges. First, we provide a spatiotemporal analysis of the CI patterns and trends for the 1980–2014 period. Subsequently, we determine the atmospheric circulation patterns that control the CI variability. In addition, we determine the geographical and low-frequency climate modes that control the CI for this mid-latitude area. In addition, we have estimated the partial dependence relationship between the CI and several geographical factors by fitting a multiple linear regression. The results from these analyses show that elevation as well as the distance from the Atlantic are the main geographical pattern that controls the CI in the Iberian Peninsula Mountain ranges. These geographical factors also reflect the role of the main atmospheric circulation patterns in the Iberian Peninsula in controlling the spatial dynamics of the CI. The Cantabrian, Iberian, and northern slopes of the Pyrenees show the lowest CI due to their exposition to northern and Atlantic circulation weather types. On the contrary, the highest CI values are found in the southern and eastern slopes of the Pyrenees, eastern slopes of Sierra Nevada, and southern slopes of the Central system. Trend analysis shows a slight increase of CI in the Central system and in the western Sierra Nevada. However, eastern Sierra Nevada, Cantabrian, Central, and Iberian show a downward CI trend. CI is principally driven by the East-Atlantic/Western Russia pattern and the North Atlantic Oscillation (NAO) in the Cantabrian, Iberian, and northern slopes of the Central range. The CI values in the Pyrenees show a different relationship with the Western Mediterranean Oscillation (WeMO) depending on whether it is the southern or the northern slope. In addition, the positive phase of the NAO oscillation controls the higher values of CI for the whole Pyrenees, especially in the mid-south part. Finally, in Sierra Nevada the CI dynamics are controlled mostly by the WeMO.This work frames within the research topics examined by the research group, MARGISNOW (PID2021-124220OB-100) funded by the Spanish Ministry of Science and Innovation. M.L.-C. is supported by a postdoctoral contract from the programme named “Programa de axudas de apoio á etapa inicial de formación posdoutoral (2022)” founded by Xunta de Galicia (Government of Galicia, Spain). Reference number: ED481B-2022-055. J.B. is supported by a pre-doctoral University Professor FPI grant (PRE2021-097046) funded by the Spanish Ministry of Science, Innovation and Universities.Peer reviewe