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  • ddc:551.6  (47)
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  • 11
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    Estimating the benefit of Doppler wind lidars for short‐term low‐level wind ensemble forecasts (2022)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2024-02-12
    Description: This work focuses on the potential of a network of Doppler lidars for the improvement of short‐term forecasts of low‐level wind. For the impact assessment, we developed a new methodology that is based on ensemble sensitivity analysis (ESA). In contrast to preceding network design studies using ESA, we calculate the explicit sensitivity including the inverse of the background covariance B matrix to account directly for the localization scale of the assimilation system. The new method is applied to a pre‐existing convective‐scale 1,000‐member ensemble simulation to mitigate effects of spurious correlations. We evaluate relative changes in the variance of a forecast metric, that is, the low‐level wind components averaged over the Rhein–Ruhr metropolitan area in Germany. This setup allows us to compare the relative variance change associated with the assimilation of hypothetical observations from a Doppler wind lidar with respect to the assimilation of surface‐wind observations only. Furthermore, we assess sensitivities of derived variance changes to a number of settings, namely observation errors, localization length scale, regularization factor, number of instruments in the network, and their location, as well as data availability of the lidar measurements. Our results demonstrate that a network of 20–30 Doppler lidars leads to a considerable variance reduction of the forecast metric chosen. On average, an additional network of 25 Doppler lidars can reduce the 1–3 hr forecast error by a factor of 1.6–3.3 with respect to 10‐m wind observations only. The results provide the basis for designing an operational network of Doppler lidars for the improvement of short‐term low‐level wind forecasts that could be especially valuable for the renewable energy sector.
    Description: This study presents the potential of a Doppler lidar network to improve short‐term low‐level wind forecasts. The approach used in this study does not require real observations and can provide valuable information for designing an operational network. The study is based on a convective‐scale 1,000‐member ensemble simulation over Germany. The results show that Doppler lidars lead to considerable variance reduction and should be considered for future observational networks.
    Description: Hans‐Ertel‐Centre for Weather Research funded by the German Federal Ministry for Transportation and Digital Infrastructure
    Description: https://doi.org/10.5281/zenodo.6331758
    Keywords: ddc:551.6 ; covariance ; data assimilation ; ensemble sensitivity analysis ; localization ; low‐level wind forecasts ; network of Doppler lidars ; observing system
    Language: English
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  • 12
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    How certain are El Niño–Southern Oscillation frequency changes in Coupled Model Intercomparison Project Phase 6 models? (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-02-06
    Description: El Niño–Southern Oscillation (ENSO) is one of the most important modes of climate variability on interannual timescales. We aim to find out whether a change in ENSO frequency can be predicted for the nearer future. We analyse the unforced pre‐industrial control run and the forced 1%/year CO〈sub〉2〈/sub〉 increase run for an ensemble of 43 general circulation models that participated in the Coupled Model Intercomparison Project Phase 6 (CMIP6). We assume that the uncertainty of ENSO frequency trend estimates from an ensemble is caused by apparent trends as well as model differences. The part of the uncertainty caused by apparent trends is estimated from the pre‐industrial control simulations. As a measure for ENSO frequency, we use the number of El Niño‐ and La Niña‐like months in a moving 30‐year time window. Its linear decadal trend is calculated for every member. The multimember mean of the trend for both experiments is less than 0.7 events per decade. Given that the standard error is of the same order of magnitude, we consider this a negligible trend. The uncertainties are large in both experiments and we can attribute most of the intermember variability to apparent trends due to natural variability rather than different model reactions to CO〈sub〉2〈/sub〉 forcing. This means that the impact of intermodel differences might have been overstated in previous studies. Apparent trends make it very difficult to make reliable predictions of changes in ENSO frequency based on 120‐year time series.
    Description: The 1pctCO2 and piControl ensembles from CMIP6 are analysed for 43 models with a focus on changes in ENSO frequency. We find that most of the intermember variability can be attributed to natural variability instead of model differences. Therefore, the uncertainty can only marginally be reduced and it is very difficult to reliably predict changes in ENSO frequency on a timescale of 150 years.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://doi.org/10.5281/zenodo.6841964
    Keywords: ddc:551.6 ; climate change ; CMIP6 ; ENSO ; ENSO frequency
    Language: English
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  • 13
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    Sea‐Ice Forecasts With an Upgraded AWI Coupled Prediction System (2022)
    Mu, Longjiang ; Nerger, Lars ; Streffing, Jan ; [et al.]
    Details
    Publication Date: 2024-02-05
    Description: A new version of the AWI Coupled Prediction System is developed based on the Alfred Wegener Institute Climate Model v3.0. Both the ocean and the atmosphere models are upgraded or replaced, reducing the computation time by a factor of 5 at a given resolution. This allowed us to increase the ensemble size from 12 to 30, maintaining a similar resolution in both model components. The online coupled data assimilation scheme now additionally utilizes sea‐surface salinity and sea‐level anomaly as well as temperature and salinity profile observations. Results from the data assimilation demonstrate that the sea‐ice and ocean states are reasonably constrained. In particular, the temperature and salinity profile assimilation has mitigated systematic errors in the deeper ocean, although issues remain over polar regions where strong atmosphere‐ocean‐ice interaction occurs. One‐year‐long sea‐ice forecasts initialized on 1 January, 1 April, 1 July and 1 October from 2003 to 2019 are described. To correct systematic forecast errors, sea‐ice concentration from 2011 to 2019 is calibrated by trend‐adjusted quantile mapping using the preceding forecasts from 2003 to 2010. The sea‐ice edge raw forecast skill is within the range of operational global subseasonal‐to‐seasonal forecast systems, outperforming a climatological benchmark for about 2 weeks in the Arctic and about 3 weeks in the Antarctic. The calibration is much more effective in the Arctic: Calibrated sea‐ice edge forecasts outperform climatology for about 45 days in the Arctic but only 27 days in the Antarctic. Both the raw and the calibrated forecast skill exhibit strong seasonal variations.
    Description: Plain Language Summary: Ocean data sparseness and systematic model errors pose problems for the initialization of coupled seasonal forecasts, especially in polar regions. Our global forecast system follows a seamless approach with refined ocean resolution in the Arctic. The new version presented here features higher computational efficiency and utilizes more ocean and sea‐ice observations. Ice‐edge forecasts outperform a climatological benchmark for about 1 month, comparable to established systems.
    Description: Key Points: We describe an upgrade of the AWI Coupled Prediction System with new ocean and atmosphere models and more observations assimilated. Independent evaluations show advances in the new version on the analysis of the sea‐ice and ocean states against the old one. Calibrated sea‐ice edge forecasts outperform a climatological benchmark for around 1 month in both hemispheres.
    Description: National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: Deutsche Forschungsgemeinschaft
    Description: https://doi.org/10.5281/zenodo.6335383
    Description: https://github.com/FESOM/fesom2/releases/tag/AWI-CM3_v3.0
    Description: https://doi.org/10.5281/zenodo.6335498
    Description: https://oasis.cerfacs.fr/en/
    Description: https://doi.org/10.5281/zenodo.4905653
    Description: http://forge.ipsl.jussieu.fr/ioserver
    Description: https://doi.org/10.5281/zenodo.6335474
    Description: http://pdaf.awi.de/
    Description: https://doi.org/10.5281/zenodo.6481116
    Keywords: ddc:551.6 ; seamless sea ice forecast ; multivariate data assimilation ; forecast calibration ; spatial probability score
    Language: English
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  • 14
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    Projected changes in synoptic circulations over Europe and their implications for summer precipitation: A CMIP6 perspective (2023)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-30
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉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.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Summer large‐scale circulations are derived over Europe using an automated classification. Spatial characteristics of the patterns and their influence on dry days are investigated. Future changes are explored based on global climate models. The predicted drier summers in Europe are found to be influenced by consistent changes in west‐easterly circulations.〈boxed-text position="anchor" content-type="graphic" id="joc8033-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:08998418:media:joc8033:joc8033-toc-0001"〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: EU International Training Network (ITN) Climate Advanced Forecasting of sub‐seasonal Extremes (CAFE)
    Description: H2020 Marie Skłodowska‐Curie Actions
    Description: https://github.com/PedroLormendez/jcclass
    Keywords: ddc:551.6 ; circulation patterns ; climate change ; precipitation ; weather extremes
    Language: English
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  • 15
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    Process-oriented analysis of aircraft soot-cirrus interactions constrains the climate impact of aviation (2021)
    Nature Publishing Group UK
    Details
    Publication Date: 2024-01-15
    Description: Fully accounting for the climate impact of aviation requires a process-level understanding of the impact of aircraft soot particle emissions on the formation of ice clouds. Assessing this impact with the help of global climate models remains elusive and direct observations are lacking. Here we use a high-resolution cirrus column model to investigate how aircraft-emitted soot particles, released after ice crystals sublimate at the end of the lifetime of contrails and contrail cirrus, perturb the formation of cirrus. By allying cloud simulations with a measurement-based description of soot-induced ice formation, we find that only a small fraction (〈1%) of the soot particles succeeds in forming cloud ice alongside homogeneous freezing of liquid aerosol droplets. Thus, soot-perturbed and homogeneously-formed cirrus fundamentally do not differ in optical depth. Our results imply that climate model estimates of global radiative forcing from interactions between aircraft soot and large-scale cirrus may be overestimates. The improved scientific understanding reported here provides a process-based underpinning for improved climate model parametrizations and targeted field observations.
    Description: Only a small part of aircraft-soot–cirrus interactions succeeds in forming cloud ice, according to simulations with a numerical cirrus cloud model. This suggests that radiative forcing from aircraft soot may have been overestimated.
    Description: https://doi.org/10.5281/zenodo.4709994
    Description: https://doi.org/10.1029/2019JD031847
    Keywords: ddc:551.6 ; Atmospheric chemistry ; Climate-change mitigation ; ice clouds formation
    Language: English
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  • 16
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    Understanding summer wind systems over the eastern Mediterranean in a high‐resolution climate simulation (2022)
    Latt, Melissa R. ; Hochman, Assaf ; Caldas‐Alvarez, Alberto ; [et al.]
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2024-01-12
    Description: Regional and local wind systems are often complex, particularly near coastal areas with a highly variable orography. Thus, the realistic representation of regional wind systems in weather and climate models is of strong relevance. Here, we evaluate the ability of a 13‐year convection‐permitting climate simulation in reproducing the interaction of several regional summer wind systems over the complex orography in the eastern Mediterranean region. The COSMO‐CLM simulations are driven by hourly ERA‐5 reanalysis and have a spatial resolution of 2.8 and 7.0 km. The simulated near‐surface wind fields are compared with unique very high‐resolution wind observations collected within the “Dead Sea Research Venue” project (DESERVE) and data from the Israel Meteorological Service synop network. The high‐resolution COSMO‐CLM simulations largely reproduce the main characteristics of the regional wind systems (Mediterranean and Dead Sea breeze, slope winds in the Judean Mountains and winds along the Jordan Rift valley), whereas ERA‐5 is only able to represent the Mediterranean Sea breeze. The high‐resolution simulations substantially improve the representation of regional winds, particularly over complex orography. Indeed, the 2.8 km simulation outperforms the 7.0 km run, on 88% of the days. Two mid‐July 2015 case studies show that only the 2.8 simulation can realistically simulate the penetration of the Mediterranean Sea Breeze into the Jordan Rift valley and complex interactions with other wind systems like the Dead Sea breeze. Our results may have profound implications for regional weather and climate prediction since very high‐resolution information seems to be necessary to reproduce the main summertime climatic features in this region. We envisage that such simulations may also be required at other regions with complex orography.
    Description: In this paper we show that COSMO‐CLM regional climate model simulations at 7.0 (CLM‐7.0) and 2.8km (CLM‐2.8) resolution can realistically reproduce near‐surface regional and local wind systems over the complex orography of the eastern Mediterranean as opposite to coarser resolutions (ERA‐5, 31 km). The Mediterranean and local Dead Sea breezes, slope winds over the Judean Mountains, and winds along the Jordan Rift valley are well represented both climatologically and on individual days. CLM‐2.8 captures the small‐scale variability of the wind field better than CLM‐7.0 particularly near the Dead Sea and on 88% of the days CLM‐2.8 represents wind speed even more realistically than CLM‐7.0. image
    Description: German Helmholtz Association (“Changing Earth” program)
    Description: AXA Research Fund http://dx.doi.org/10.13039/501100001961
    Description: Ministry of Science, Research and Arts
    Description: Helmholtz Association of German Research Centers
    Keywords: ddc:551.6 ; complex orography ; convection permitting ; COSMO‐CLM ; Dead Sea ; eastern Mediterranean ; grid spacing ; regional climate modelling ; sea breeze
    Language: English
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  • 17
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    Assessing Precipitation Over the Amazon Basin as Simulated by a Storm‐Resolving Model (2023)
    Details
    Publication Date: 2023-12-19
    Description: In this study, we investigate whether a better representation of precipitation in the Amazon basin arises through an explicit representation of convection and whether it is related to the representation of organized systems. In addition to satellite data, we use ensemble simulations of the ICON‐NWP model at storm‐resolving (2.5–5.0 km) scales with explicit convection (E‐CON) and coarse resolutions, with parameterized convection (P‐CON). The main improvements in the representation of Amazon precipitation by E‐CON are in the distribution of precipitation intensity and the spatial distribution in the diurnal cycle. By isolating precipitation from organized convective systems (OCS), it is shown that many of the well simulated precipitation features in the Amazon arise from the distribution of these systems. The simulated and observed OCS are classified into 6 clusters which distinguish nocturnal and diurnal OCS. While the E‐CON ensembles capture the OCS, especially their diurnal cycle, their frequency is reduced compared to observations. Diurnal clusters are influenced by surface processes such as cold pools, which aid to the propagation of OCS. Nocturnal clusters are rather associated with strong low‐level easterlies, possibly related to the Amazonian low‐level jet. Our results also show no systematic improvement with a twofold grid refinement and remaining biases related to stratiform features of OCS suggest that yet unresolved processes play an important role for correctly representing precipitating systems in the Amazon.
    Description: Plain Language Summary: The Amazon basin is a relevant element of the Earth system because it influences the global water and carbon cycle, as well as it constitutes a unique ecosystem. Over this important region, conventional climate models do not simulate basic features of rainfall given their inability to resolve this physical process due to their coarse spatial resolution. In this study, we use high‐resolution simulations that allow an explicit representation of such physical process (moist convection) and compare them with a set of coarse‐resolution simulations and observed precipitation. We find that improvements in the representation of Amazon rainfall, such as the distribution of light and high intensity rain rates, as well as the spatial variability of the diurnal cycle, are explained by the explicit representation of moist convection. Moreover, these improvements arise from the representation of big and organized systems that produce intense rainfall (OCS). We find that particular environmental conditions are associated with the OCS according to their time of occurrence. Diurnal OCS are mainly influenced by interactions with the surface, while nocturnal OCS are related to strong low‐level winds. Some of the remaining discrepancies with observed OCS do not show improvements when refining the grid by a factor of two.
    Description: Key Points: An explicit representation of convection enables the emergence of organized systems (OCS) leading to improved simulations of Amazon rainfall. Propagating cold‐pools and strong low‐level easterlies are related to the occurrence of diurnal and nocturnal OCS, respectively. Systematic biases in the size, intensity and nocturnal precipitation phase of OCS are insensitive to a twofold refinement in resolution.
    Description: Max Planck Society for the Advancement of Science
    Description: European Horizon 2020 project CONSTRAIN
    Description: https://www.metoffice.gov.uk/hadobs/hadisst/data/download.html
    Description: https://www.ncei.noaa.gov/data/cmorph-high-resolution-global-precipitation-estimates/access/30min/8km
    Description: https://www.hydrosheds.org/products/hydrobasins
    Description: https://esgf-data.dkrz.de/projects/cmip6-dkrz/
    Description: https://pure.mpg.de/
    Keywords: ddc:551.6 ; Amazon rainfall ; organized precipitating systems ; storm‐resolving simulation
    Language: English
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  • 18
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    High‐resolution in situ stable isotope measurements reveal contrasting atmospheric vapour dynamics above different urban vegetation (2023)
    John Wiley & Sons, Inc. | Hoboken, USA
    Details
    Publication Date: 2023-12-19
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉We monitored stable water isotopes in liquid precipitation and atmospheric water vapour (δ〈sub〉v〈/sub〉) using in situ cavity ring‐down spectroscopy (CRDS) over a 2 month period in an urban green space area in Berlin, Germany. Our aim was to better understand the origins of atmospheric moisture and its link to water partitioning under contrasting urban vegetation. δ〈sub〉v〈/sub〉 was monitored at multiple heights (0.15, 2 and 10 m) in grassland and forest plots. The isotopic composition of δ〈sub〉v〈/sub〉 above both land uses was highly dynamic and positively correlated with that of rainfall indicating the changing sources of atmospheric moisture. Further, the isotopic composition of δ〈sub〉v〈/sub〉 was similar across most heights of the 10 m profiles and between the two plots indicating high aerodynamic mixing. Only at the surface at ~0.15 m height above the grassland δ〈sub〉v〈/sub〉 showed significant differences, with more enrichment in heavy isotopes indicative of evaporative fractionation especially after rainfall events. Further, disequilibrium between δ〈sub〉v〈/sub〉 and precipitation composition was evident during and right after rainfall events with more positive values (i.e., values of vapour higher than precipitation) in summer and negative values in winter, which probably results from higher evapotranspiration and more convective precipitation events in summer. Our work showed that it is technically feasible to produce continuous, longer‐term data on δ〈sub〉v〈/sub〉 isotope composition in urban areas from in situ monitoring using CRDS, providing new insights into water cycling and partitioning across the critical zone of an urban green space in Central Europe. Such data have the potential to better constrain the isotopic interface between the atmosphere and the land surface and to thus, improve ecohydrological models that can resolve evapotranspiration fluxes.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉In situ measurements of urban atmospheric water isotopes (δ〈sub〉v〈/sub〉) at different heights produce reliable and stable high‐resolution data. Urban atmospheric vapour is influenced by varying drivers depending on the type of green space. δ〈sub〉v〈/sub〉 above grassland and tree stands was similar at 10 m height, but near‐surface δ〈sub〉v〈/sub〉 indicated higher evaporation and vapour enrichment over grass. We detected occasional dis‐equilibrium between vapour and precipitation isotopes.〈boxed-text position="anchor" content-type="graphic" id="hyp14989-blkfxd-0001" xml:lang="en"〉 〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:08856087:media:hyp14989:hyp14989-toc-0001"〉 〈/graphic〉 〈/boxed-text〉〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Einstein Stiftung Berlin http://dx.doi.org/10.13039/501100006188
    Description: Leverhulme Trust http://dx.doi.org/10.13039/501100000275
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Description: Einstein Research Unit
    Description: Einstein Foundation Berlin and Berlin University Alliance
    Description: BiNatur
    Description: BMBF http://dx.doi.org/10.13039/501100002347
    Description: Leverhulme Trust through the ISO‐LAND project
    Keywords: ddc:551.6 ; atmospheric vapour isotopes ; cities ; ecohydrology ; equilibrium assumption ; in situ monitoring ; urban green spaces
    Language: English
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  • 19
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    On the representation of atmospheric circulation modes in regional climate models over Western Europe (2022)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2023-12-16
    Description: Atmospheric circulation is a key driver of climate variability, and the representation of atmospheric circulation modes in regional climate models (RCMs) can enhance the credibility of regional climate projections. This study examines the representation of large‐scale atmospheric circulation modes in Coupled Model Inter‐comparison Project phase 5 RCMs once driven by ERA‐Interim, and by two general circulation models (GCMs). The study region is Western Europe and the circulation modes are classified using the Promax rotated T‐mode principal component analysis. The results indicate that the RCMs can replicate the classified atmospheric modes as obtained from ERA5 reanalysis, though with biases dependent on the data providing the lateral boundary condition and the choice of RCM. When the boundary condition is provided by ERA‐Interim that is more consistent with observations, the simulated map types and the associating time series match well with their counterparts from ERA5. Further, on average, the multi‐model ensemble mean of the analysed RCMs, driven by ERA‐Interim, indicated a slight improvement in the representation of the modes obtained from ERA5. Conversely, when the RCMs are driven by the GCMs that are models without assimilation of observational data, the representation of the atmospheric modes, as obtained from ERA5, is relatively less accurate compared to when the RCMs are driven by ERA‐Interim. This suggests that the biases stem from the GCMs. On average, the representation of the modes was not improved in the multi‐model ensemble mean of the five analysed RCMs driven by either of the GCMs. However, when the best‐performed RCMs were selected on average the ensemble mean indicated a slight improvement. Moreover, the presence of the North Atlantic Oscillation (NAO) in the simulated modes depends also on the lateral boundary conditions. The relationship between the modes and the NAO was replicated only when the RCMs were driven by reanalysis. The results indicate that the forcing model is the main factor in reproducing the atmospheric circulation.
    Keywords: ddc:551.6 ; general circulation model ; large‐scale atmospheric circulation modes ; multi‐model ensemble ; regional climate model ; Western Europe
    Language: English
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  • 20
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    European Summer Synoptic Circulations and Their Observed 2022 and Projected Influence on Hot Extremes and Dry Spells (2023)
    Details
    Publication Date: 2023-12-16
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉In 2022, western Europe experienced its hottest summer on record and widespread dry conditions, with substantial impacts on health, water and vegetation. We use a reanalysis to classify daily mean sea level pressure fields and to 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 partially 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〉
    Description: Plain Language Summary: In 2022, western Europe recorded its hottest summer up to date since preindustrial times. At the same time, widespread dry conditions caused dramatic impacts on human health, water resources, crop yields and wildfires. This was partly enhanced by the human–caused cumulative emissions of greenhouse gases, but also potentially by large‐scale circulation anomalies that may also be triggered by global warming. By grouping distinct weather patterns, we find that many extreme hot days during the summer of 2022 over well‐defined parts of Europe were favored by anomalous transport of hot and dry air masses or persistent low‐wind conditions. These weather patterns were essential but not the dominant factor that led to the occurrence of extreme temperatures. Yet, they played a key role in enhancing the number of dry days. We also find that the weather patterns observed in summer 2022 will become more common in coming decades if greenhouse gas emissions remain without reduction. This would further worsen hot and dry extremes in summer over Europe.〈/p〉
    Description: Key Points : 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉European summer 2022 hot extremes have been enhanced by an anomalous occurrence of distinct circulation types over different subdomains〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Predominant circulation anomalies also contributed to the exceptional number of dry days, as much as local, mostly thermodynamical effects〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Such anomalous circulations will become more common, thus further worsening European hot and dry extremes〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: HORIZON EUROPE Marie Sklodowska‐Curie Actions http://dx.doi.org/10.13039/100018694
    Description: https://doi.org/10.24381/cds.adbb2d47
    Description: https://doi.org/10.5194/gmd-9-1937-2016
    Keywords: ddc:551.6 ; hot summer 2022 ; hot extremes ; circulation types ; circulation classification ; climate change ; atmospheric circulation
    Language: English
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