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  • 1
    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
    Type: doc-type:article
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  • 2
    Publication Date: 2024-04-25
    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"〉Dansgaard‐Oeschger (D‐O) climate variability during the last glaciation was first evidenced in ice cores and marine sediments, and is also recorded in various terrestrial paleoclimate archives in Europe. The relative synchronicity across Greenland, the North Atlantic and Europe implies a tight and fast coupling between those regions, most probably effectuated by an atmospheric transmission mechanism. In this study, we investigated the atmospheric changes during Greenland interstadial (GI) and stadial (GS) phases based on regional climate model simulations using two specific periods, GI‐10 and GS‐9 both around 40 ka, as boundary conditions. Our simulations accurately capture the changes in temperature and precipitation as reconstructed by the available proxy data. Moreover, the simulations depict an intensified and southward shifted eddy‐driven jet during the stadial period. Ultimately, this affects the near‐surface circulation toward more southwesterly and cyclonic flow in western Europe during the stadial period, explaining much of the seasonal climate variability recorded by the proxy data, including oxygen isotopes, at the considered proxy sites.〈/p〉
    Description: Plain Language Summary: The climate during the last ice age varied between colder and warmer periods on timescales ranging from hundreds to thousands of years. This variability was first detected in Greenland ice cores and marine sediment cores of the North Atlantic, as well as in continental geological records in Europe. The variation between the colder and warmer periods occur mostly simultaneously in Greenland and in Europe, which is why the atmosphere is assumed to have an important role in transferring the climate signals. We simulated two different periods of the last ice age, one colder and one warmer around 40,000 years ago, using a regional climate model. The aim was to study how the climate and atmospheric circulation changed during these two periods. We find the eddy‐driven jet over the North Atlantic intensified and shifted southward during the colder period. The jet influences the near‐surface atmospheric circulation and leads to more southwesterly and cyclonic flow in western Europe. Oxygen isotope variations observed in western European paleoclimate records may be partly explained by different, more southern moisture sources on top of changes in seasonal temperatures.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Simulated temperatures agree with proxy data; precipitation is biased but GI‐10 versus GS‐9 differences are well captured〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉The stadial winter jet stream is intensified and shifted southward, consistent with dominant southwesterly/cyclonic flow in western Europe〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Oxygen isotope signal changes at western European proxy sites may be explained not only by temperature but also by varying moisture sources〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: NRDIO
    Description: AXA Research Fund http://dx.doi.org/10.13039/501100001961
    Description: https://doi.org/10.5065/1dfh-6p97
    Keywords: ddc:551.6 ; Dansgaard‐Oeschger cycle ; regional atmospheric dynamics ; regional climate modeling ; continental paleoclimate proxy ; Europe
    Language: English
    Type: doc-type:article
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  • 3
    Publication Date: 2022-03-31
    Description: Compound weather and climate events are combinations of climate drivers and/or hazards that contribute to societal or environmental risk. Studying compound events often requires a multidisciplinary approach combining domain knowledge of the underlying processes with, for example, statistical methods and climate model outputs. Recently, to aid the development of research on compound events, four compound event types were introduced, namely (a) preconditioned, (b) multivariate, (c) temporally compounding, and (d) spatially compounding events. However, guidelines on how to study these types of events are still lacking. Here, we consider four case studies, each associated with a specific event type and a research question, to illustrate how the key elements of compound events (e.g., analytical tools and relevant physical effects) can be identified. These case studies show that (a) impacts on crops from hot and dry summers can be exacerbated by preconditioning effects of dry and bright springs. (b) Assessing compound coastal flooding in Perth (Australia) requires considering the dynamics of a non‐stationary multivariate process. For instance, future mean sea‐level rise will lead to the emergence of concurrent coastal and fluvial extremes, enhancing compound flooding risk. (c) In Portugal, deep‐landslides are often caused by temporal clusters of moderate precipitation events. Finally, (d) crop yield failures in France and Germany are strongly correlated, threatening European food security through spatially compounding effects. These analyses allow for identifying general recommendations for studying compound events. Overall, our insights can serve as a blueprint for compound event analysis across disciplines and sectors.
    Description: Plain Language Summary: Many societal and environmental impacts from events such as droughts and storms arise from a combination of weather and climate factors referred to as a compound event. Considering the complex nature of these high‐impact events is crucial for an accurate assessment of climate‐related risk, for example to develop adaptation and emergency preparedness strategies. However, compound event research has emerged only recently, therefore our ability to analyze these events is still limited. In practice, studying compound events is a challenging task, which often requires interaction between experts across multiple disciplines. Recently, compound events were divided into four types to aid the framing of research on this topic, but guidelines on how to study these four types are missing. Here, we take a pragmatic approach and—focusing on case studies of different compound event types—illustrate how to address specific research questions that could be of interest to users. The results allow identifying recommendations for compound event analyses. Furthermore, through the case studies, we highlight the relevance that compounding effects have for the occurrence of landslides, flooding, vegetation impacts, and crop failures. The guidelines emerged from this work will assist the development of compound event analysis across disciplines and sectors.
    Description: Key Points: Using case studies representative of four main compound event types we show how compound event‐related research questions can be tackled. We present user‐friendly guidelines for compound event analysis applicable to different compound event types. We demonstrate that compound events cause vegetation impacts, coastal flooding, landslides, and continental‐scale crop yield failures.
    Description: European COST action DAMOCLES
    Description: NERC
    Description: Swiss National Science Foundation
    Description: Helmholtz Initiative and Networking Fund
    Description: Netherlands Organisation for Scientific Research (NWO)
    Description: Fundação para a Ciência e a Tecnologia
    Description: Scientific Employment Stimulus 2017
    Description: Italian Ministry of University and Research
    Description: European Union's Horizon 2020 research and innovation programme
    Description: AXA Research Fund for support
    Description: Portuguese Foundation for Science and Technology
    Keywords: ddc:551.6
    Language: English
    Type: doc-type:article
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