The Mediterranean region is strongly affected by extreme precipitation events (EPEs), sometimes leading to severe negative impacts on society, economy, and the environment. Understanding such natural hazards and their drivers is essential to mitigate related risks. Here, EPEs over the Mediterranean between 1979 and 2019 are analysed, using ERA5, the latest reanalysis dataset from ECMWF. EPEs are determined based on the 99th percentile of their daily distribution (P99). The different EPE characteristics are assessed, based on seasonality and spatiotemporal dependencies. To better understand their connection to large‐scale atmospheric flow patterns, Empirical Orthogonal Function analysis and subsequent non‐hierarchical K‐means clustering are used to quantify the importance of weather regimes to EPE frequency. The analysis is performed for different variables, depicting atmospheric variability in the lower and middle troposphere. Results show a clear spatial division in EPE occurrence, with winter and autumn being the seasons of highest EPE frequency for the eastern and western Mediterranean, respectively. There is a high degree of temporal dependencies with 20% of the EPEs (median value based on all studied grid cells), occurring up to 1 week after a preceding P99 event at the same location. Local orography is a key modulator of the spatiotemporal connections and substantially enhances the probability of co‐occurrence of EPEs even for distant locations. The clustering clearly demonstrates the prevalence of distinct synoptic‐scale atmospheric conditions during the occurrence of EPEs for different locations within the region. Results indicate that clustering, based on a combination of sea level pressure (SLP) and geopotential height at 500 hPa (Z500), can increase the conditional probability of EPEs by more than three (3) times (median value for all grid cells) from the nominal probability of 1% for the P99 EPEs. Such strong spatiotemporal dependencies and connections to large‐scale patterns can support extended‐range forecasts.

Projected changes in summer precipitation deficits partly depend on alterations in synoptic circulations. Here, the automated Jenkinson–Collison classification is used to assess the ability of 21 global climate models (GCMs) to capture the frequency of recurring circulation types (CTs) and their implications for European daily precipitation amounts in summer (JJA). The ability of the GCMs to reproduce the observed present‐day climate features is evaluated first. Most GCMs capture the observed links between the mean CTs directional flow characteristics and the occurrence of dry days and related dry months. The most robust relationships are found for anticyclonic and easterly CTs which are generally associated with higher‐than‐average occurrences of dry conditions. Future changes in summer CTs' frequencies are estimated in the high‐emission SSP5‐8.5 scenario for the sake of a high signal‐to‐noise ratio. Our results reveal consistent changes, mainly in the zonal CTs. A robust decrease in frequency of the westerlies and an increase in the frequency of easterly CTs favour more continental, dry and warm air masses over central Europe. These dynamical changes are shown to enhance the projected summer drying over central and southern Europe.

While the evidence for anthropogenic climate change continues to strengthen, and concerns about severe weather events are increasing, global projections of regional climate change are still uncertain due to model‐dependent changes in large‐scale atmospheric circulation, including over North Atlantic and Europe. Here, the Jenkinson–Collison classification of daily circulation patterns is used to evaluate past and future changes in their seasonal frequencies over Central Europe for the 1900–2100 period. Three reanalyses and eight global climate models from the Coupled Model Intercomparison Project phase 6, were used based on daily mean sea‐level pressure data. Best agreement in deriving relative frequencies of the synoptic types was found between the reanalyses. Global models can generally capture the interannual variability of circulation patterns and their climatological state, especially for the less frequent synoptic types. Based on historical data and the shared socioeconomic pathway 5 scenario, the evaluated trends show more robust signals during summer, given their lesser internal variability. Increasing frequencies were found for circulation types characterized by weak pressure gradients, mainly at the expense of decreasing frequencies of westerlies. Our findings indicate that given a high‐emission scenario, these signals will likely emerge from past climate variability towards the mid‐21st century for most altered circulation patterns.

In 2022, western Europe experienced its hottest summer on record and widespread dry conditions, with substantial impacts on health, water and vegetation. Here we use a reanalysis to classify daily mean sea level pressure fields and investigate the influence of synoptic circulations on the occurrence of temperature extremes and dry days. Summer 2022 featured an above-normal occurrence of anticyclones extending from the British Isles to the Baltic countries, as well as enhanced easterly, southerly and low-flow conditions which contributed to the observed extremes over southern and western Europe. While the hot summer of 2022 is only marginally explained by circulation anomalies, such anomalies played a key role in the exceptional occurrence of dry days. The comparison with summer circulation anomalies projected by twenty global climate models moreover suggests that future circulation changes will further exacerbate hot and dry extremes over Europe.

<p>Automated classifications of atmospheric circulations are a well-known tool to characterize large-scale patterns that predominantly determine day-to-day weather variations. Through its potential influence on the relative frequency of circulation patterns, global warming can also enhance or mitigate the occurrence of extreme weather events.</p><p>Here, we use a subset of 22 CMIP6  global climate models (GCMs) to assess their ability to capture these recurrent circulation patterns and their implication for the European climate and its projected changes.</p><p>We investigate links between synoptic circulations and short-term meteorological drought events that span one month. We employ the automated Jenkinson-Collison classification to determine daily atmospheric features based on mean sea-level pressure. We compute the conditional probability of dry days related to each circulation type. Furthermore, we confirm the influence of these patterns on the occurrence of dry months by computing the monthly relative frequency anomalies of the synoptic circulations given months where the Standardized Precipitation Index (SPI) was below minus 1. We evaluate the ability of the historical runs of global climate models (GCMs) to reproduce the observed features from the ERA5 reanalyses over the 1961-1990 reference period. Links between the mean directional flow characteristics of the circulation types and the dry days and months are well represented by most GCMs. The most robust relationships were found for the anticyclonic, easterly, and low flow types. These circulations are generally associated with a lack of precipitation and therefore show higher than average occurrences during dry months. </p>