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Recent Arctic warming has fuelled interest in the weather and climate of the polar regions and how this interacts with lower latitudes. Several interesting theories of polar-midlatitude linkages involves Rossby wave propagation as a key process even though the meridional gradient in planetary vorticity, crucial for these waves, is weak at high latitudes. Here we review some basic theory and suggest that Rossby waves can indeed explain some features of polar variability, especially when relative vorticity gradients are present. We suggest that large-scale polar flow can be conceptualised as a mix of geostrophic turbulence and Rossby wave propagation, as in the mid-latitudes, but with the balance tipped further in favour of turbulent flow. Hence, isolated vortices often dominate but some wavelike features remain. As an example, quasi-stationary or weakly westward-propagating subpolar anomalies emerge from statistical analysis of observed data, and these are consistent with some role for wave propagation. The noted persistence of polar cyclones and anticyclones is attributed in part to the weakened effects of wave dispersion, the mechanism responsible for the decay of mid-latitude anomalies in downstream development. We also suggest that the vortex-dominated nature of polar dynamics encourages the emergence of annular mode structures in principal component analyses of extratropical circulation. Finally, we consider how Rossby waves may be triggered from high latitudes. The linear mechanisms known to balance localised heating at lower latitudes are shown to be less efficient in the polar regions. Instead, we suggest the direct response to sea ice loss often manifests as a heat low, with radiative cooling balancing the heating. If the relative vorticity gradient is favourable this does have the potential to trigger a Rossby wave response, although this will often be weak compared to waves forced from lower latitudes.

The loss of thick multiyear sea ice in the Arctic leads to weaker sea ice that is more easily broken up by strong winds. As a consequence, extreme sea ice breakup events may become more frequent, even during the middle of winter when the sea ice cover is frozen solid. This can lead to an earlier onset of the melt season and potentially accelerate Arctic sea ice loss. Such extreme breakup events are generally not captured by climate models, potentially limiting our confidence in projections of Arctic sea ice. We investigated the driving forces behind sea ice breakup events during winter and how they change in a future climate. Our sea ice model is the first to reproduce such breakup events and reveals that the combination of strong winds and thin sea ice is a key factor for these breakups. We found that winter breakups have a large effect on local heat and moisture transfer and cause enhanced sea ice production, but also increase the overall movement of the sea ice cover, making it more vulnerable. Finally, we show that if the Arctic sea ice continues to thin, these extreme breakup events could become even more frequent.

One of the most intense air mass transformations on Earth happens when cold air flows from frozen surfaces to much warmer open water in cold-air outbreaks (CAOs), a process captured beautifully in satellite imagery. Despite the ubiquity of the CAO cloud regime over high-latitude oceans, we have a rather poor understanding of its properties, its role in energy and water cycles, and its treatment in weather and climate models. The Cold-Air Outbreaks in the Marine Boundary Layer Experiment (COMBLE) was conducted to better understand this regime and its representation in models. COMBLE aimed to examine the relations between surface fluxes, boundary layer structure, aerosol, cloud, and precipitation properties, and mesoscale circulations in marine CAOs. Processes affecting these properties largely fall in a range of scales where boundary layer processes, convection, and precipitation are tightly coupled, which makes accurate representation of the CAO cloud regime in numerical weather prediction and global climate models most challenging. COMBLE deployed an Atmospheric Radiation Measurement Mobile Facility at a coastal site in northern Scandinavia (69°N), with additional instruments on Bear Island (75°N), from December 2019 to May 2020. CAO conditions were experienced 19% (21%) of the time at the main site (on Bear Island). A comprehensive suite of continuous in situ and remote sensing observations of atmospheric conditions, clouds, precipitation, and aerosol were collected. Because of the clouds’ well-defined origin, their shallow depth, and the broad range of observed temperature and aerosol concentrations, the COMBLE dataset provides a powerful modeling testbed for improving the representation of mixed-phase cloud processes in large-eddy simulations and large-scale models.

This paper introduces the Bergen Dynamical Model (Bedymo), an idealized atmospheric circulation model, which combines the quasi-geostrophic approximation and the hydrostatic primitive equations into one modelling framework. The model is designed such that the two systems of equations are solved as similarly as possible, such that differences can be unambiguously attributed to the different approximations, rather than the model formulation or the numerics. As a consequence, but in contrast to most other quasi-geostrophic models, Bedymo uses σ coordinates in the vertical. In addition to the atmospheric core, Bedymo also includes a slab ocean model with options for prescribed and wind-induced currents. Further, Bedymo has a graphical user interface, making it particularly useful for teaching. Bedymo is evaluated for four atmosphere-only test cases and one coupled test case including the slab ocean component. The atmosphere-only test cases comprise the growth of a cyclonic disturbance in a baroclinic environment and the excitation of Rossby waves and inertia–gravity waves by isolated orography, as well as the simulation of a mid-latitude storm track, all in a mid-latitude channel. The atmosphere–ocean coupled test case is based on an equatorial channel and evaluates the coupled response to an isolated equatorial temperature anomaly in the ocean mixed layer. For all test cases, results agree well with expectations from theory and results obtained with more complex models.

Cyclone clustering, the swift succession of multiple extratropical cyclones, constitutes a large fraction of European weather extremes. To investigate the dynamical causes of cyclone clustering, it is necessary to diagnose the occurrence of cyclone clustering and to determine their characteristics. So far, most diagnostics focused either on local impact or on a statistical analysis of storm recurrence. While the first cannot be applied globally, the latter is difficult to relate to individual events. We therefore use a novel method to globally detect cyclone clustering that is closer to the original concept of Bjerknes and Solberg, where extratropical cyclones follow similar tracks within a given time period.Using this novel cyclone clustering diagnostic based on spatio-temporal distance between cyclone tracks, we analyse cyclone clustering globally in Era-Interim for the period 1979 until 2016 as well as for 10 CMIP6 models. We separate the cyclone clusters into two types: one representing the ‘classical’ bjerknes-type clusters, and one representing more stationary clusters. We find that cyclone clustering mainly occurs along the climatological storm tracks, with the bjerknes-type more common at the western side of the storm tracks, while the stationary-type of cyclone clusters occurs more downstream. In general, clustered cyclones are stronger than non-clustered cyclones. While CMIP6 models feature a slight bias towards an equatorward shift of the storm tracks, cyclone clustering in a future climate occurs more poleward. Furthermore, the average number of storms per cluster decreases in a future climate, though the mean intensity of the cyclones that are clustered increases slightly., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Marine cold-air outbreaks (CAO) are vigorous equatorward excursions of coldair over the ocean, responsible for the majority of wintertime oceanic heat lossfrom the subpolar seas of the North Atlantic. However, the impact of individualCAO events on the ocean is poorly understood. Here we present the first coupledobservations of the atmosphere and ocean during a wintertime CAO event,between 28 February and 13 March 2018, in the subpolar North Atlantic region.Comprehensive observations are presented from five aircraft flights, a researchvessel, a meteorological buoy, a subsurface mooring, an ocean glider, and anArgo float. The CAO event starts abruptly with substantial changes in temperature,humidity and wind throughout the atmospheric boundary layer. The CAOiswell mixed vertically and, away from the sea-ice edge, relatively homogeneousspatially. During the CAO peak, higher sensible heat fluxes occupy at least thelowest 200m of the atmospheric boundary layer, while higher latent heat fluxesare confined to the surface layer. The response of the ocean to the CAO is spatiallydependent. In the interior of the Iceland Sea the mixed layer cools, while inthe boundary current region itwarms. In both locations, the mixed layer deepensand becomes more saline. Combining our observations with one-dimensionalmixed-layer modelling, we show that in the interior of the Iceland Sea, atmosphericforcing dominates the ocean response. In contrast, in the boundarycurrent region lateral advection and mixing counteract the short-term impact ofthe atmospheric forcing. Timeseries observations of the late-winter period illustratea highly variable ocean mixed layer, with lateral advection and mixing oftenmasking the ocean’s general cooling and deepening response to individual CAOevents., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The Gulf Stream and Kuroshio regions feature strong sea surface temperature (SST) gradients that influence cyclone development and the storm track. Previous studies showed that smoothing the SSTs in either the North Atlantic or North Pacific yields a reduction in cyclone activity, surface heat fluxes, and precipitation, as well as a southward shift of the storm track and the upper-level jet. To what extent these changes are attributable to changes in individual cyclone behaviour, however, remains unclear. Comparing simulations with realistic and smoothed SSTs in the atmospheric general circulation model AFES, we find that the intensification of individual cyclones in the Gulf Stream or Kuroshio region is only marginally affected by reducing the SST gradient. In contrast, we observe considerable changes in the climatological mean state as well as a reduced cyclone activity in the North Atlantic and North Pacific storm tracks that are shifted equatorward in both basins. The upper-level jet in the Atlantic also shifts equatorward, while the jet in the Pacific strengthens in its climatological position and extends further east. Surface heat fluxes, specific humidity, and precipitation also respond strongly to the smoothing of the SST, with a considerable decrease in their mean values on the warm side of the SST front. This decrease is more pronounced in the Gulf Stream than in the Kuroshio region, due to the larger decrease in SST along the Gulf Stream SST front. Considering the differences of the different variables occurring within/outside of a 750 km radius of any cyclone over their entire lifetime, we find that cyclones play only a secondary role in explaining the differences in the mean state between the smoothed and realistic SST experiments.

Location choice is a crucial planning task with major influence on a company’s future orientation and competitiveness. It is quite complex, since multiple location factors are usually of decision-relevance, incomparable, and sometimes conflictual. Further, ongoing urbanization is associated with locational dynamics posing major challenges for the regional location management of companies and municipalities. For example, respecting urban space as location factor, a scarcity growing over time leads to different assessment and requirements on a company’s behalf. For both companies and municipalities, there is a need for location development which implies an active change of location factor characteristics. Accordingly, considering locational dynamics is vital, as they may be decisive in the location decision-making. Although certain dynamics are considered within conventional Facility Location Problem (FLP) approaches, a systematic consideration of active location development is missing so far. Consequently, they may propagate long-term unfavorable location decisions, as major potentials associated with company-driven and municipal development measures are neglected. Therefore, this paper introduces a comprehensive decision support framework for the Regional Facility Location and Development planning Problem (RFLDP). It provides an operationalization of development measures, and thus anticipates dynamic adaptations to the environment. An established multi-criteria approach is extended to this new application. A complementary guideline ensures its meaningful applicability by practitioners. Based on a real-life case study, the decision support framework’s strength for practical application is demonstrated. Here, major advantages over conventional FLP approaches are highlighted. It is shown that the proposed methodology results in alternative location decisions which are structurally superior.

International audience; Arctic sea ice is thinning (Meier, 2017) in conjunction with the decrease in the area covered by thick multiyear ice (MYI) (Kwok, 2018), which is replaced by thinner first-year ice (FYI) that is more mobile and less dynamically stable (Rampal et al., 2009; J. Zhang et al., 2012). This makes the ice cover more vulnerable to intense winds breaking up the sea ice. In the Beaufort Sea in particular, the loss of MYI may contribute to the earlier onset of the melt season in recent years (Johnson & Eicken, 2016). When sea ice breaks up, it exposes the underlying warmer ocean within narrow, linear openings in the ice cover known as leads. This has important consequences for air-sea exchange, ocean eddy generation and dynamics, sea ice production, and Arctic Ocean properties in general (Cohanim et al., 2021; Graham et al., 2019; Nguyen et al., 2009), especially during the winter months when heat fluxes over sea ice are generally small (Andreas & Cash, 1999). In addition, breakup in winter weakens the ice cover, potentially preconditioning the minimum ice extent in summer (Y. Zhang et al., 2018; Babb et al., 2019) and thus creating a positive feedback to Arctic amplification (Dai et al., 2019). Therefore, extreme breakup events are of crucial interest for understanding the seasonal and long-term evolution of Arctic sea ice, which in turn affect weather, ecosystems, and local communities in polar regions and beyond (Forbes et al., 2016; Vihma, 2014).

Werden Anpassungen von Produktionssystemen geplant, beispielsweise der Bau einer neuen Anlage, werden häufig Simulationen für die Prognose der damit verbundenen Auswirkungen genutzt. So wird die Basis für eine betriebswirtschaftliche Bewertung geschaffen. Für die Erstellung der Modelle werden Entscheidungsprozesse der Produktionsplanung und -steuerung in der Simulation dargestellt, beispielsweise die Reihenfolgenplanung einer Anlage. Diese Übertragung der Entscheidungsprozesse in die Simulation führt zu einem hohen Aufwand für die Erstellung von Simulationsmodellen. Dieser Aufwand kann durch die Nutzung iterativer optimierungsbasierter Simulationen verringert werden, da hier auf bereits existierende Prozesse zurückgegriffen wird. Statt Entscheidungsprozesse in der Simulation neu zau modellieren und lösen, wird die Simulation mit Optimierungsverfahren gekoppelt, die auch im realen System zur Entscheidungsfindung genutzt werden. Dieses Konzept wird bei einem Stahlhersteller angewendet und es wird gezeigt, dass so verschiedene operative bis taktische Anpassungen bewertet werden können.

To reduce the high impacts of lithium-ion batteries, closed-loop supply chains using recycling and reuse are established. Simultaneously, car manufacturers face legal requirements based on the carbon emissions of their products. Therefore, these manufacturers aim to reduce carbon emissions in their entire supply chain. Hence, CO2-penalty costs in the form of taxes or contractual penalties are likely to be inforced. To analyze their effects, we formulate a model for the integrated production and recycling planning. By applying the model to an illustrative case study, it is shown that the level of the penalty costs influences carbon emissions.

The need for sustainable mobility requires measures to reduce the impacts along the product life cycle. One mitigation option is the closed-loop use of products, components and materials, with resulting increased interactions and interdependencies between production and recycling. Research focusses generally on individual planning tasks and levels and does not consider production and recycling simultaneously. Therefore, we develop a coordinated planning approach for closed-loop supply chains which considers interdependencies in the form of directives, feedback, and coordination between the forward and reverse supply chain. Concluding, the approach is discussed in the context of lithium-ion batteries.

Durch die zunehmende Digitalisierung der Wertschöpfungskette werden Unternehmen mit neuen Herausforderungen, wie etwa einer höheren Variantenvielfalt oder steigenden Individualisierungswünschen von Kunden, konfrontiert. Zur Bewältigung der wachsenden Herausforderungen bietet die Implementierung von Industrie 4.0-Lösungen großes Potenzial. Dennoch agieren gerade kleine und mittlere Unternehmen bei deren Einführung zurückhaltend. Dies ist vor allem auf den hohen finanziellen Aufwand für Industrie 4.0-Lösungen und eine unzureichende Abschätzbarkeit der Auswirkungen ihrer Einführung zurückzuführen. Im Rahmen des EFRE-Forschungsprojekts »Synus« wurden Methoden und Tools zur Unterstützung von kleinen und mittleren Unternehmen bei der Bewertung und Auswahl von Industrie 4.0-Lösungen entwickelt. Inhalt dieses Beitrags ist die Präsentation des Potenzial-Modells, welches kleine und mittlere Unternehmen zur Auswahl geeigneter Industrie 4.0-Lösungen in Abhängigkeit der individuellen Sachlagen und Präferenzen befähigt.

Rapid changes in the sea ice cover are commonly attributed to periods of strong winds, which in turn are often associated with cyclones and their fronts. In addition to geographically redistributing sea ice, and thereby potentially increasing its export from the Arctic, cyclones also transport moist warm air masses into the Arctic which can lead to local sea ice melt while the cyclone’s cold sector might lead to freezing and sea ice formation. Furthermore, cold air outbreaks associated with the withdrawal of cold air masses over the open ocean usually lead to sea-ice formation. The relative contribution of these competing effects of weather events on the sea ice is so far poorly understood.We climatologically assess these competing effects of cyclones on sea ice using detected cyclones, fronts, and cold-air outbreaks in the coupled ECMWF CERA-SAT reanalyses. We then decompose the climatological sea-ice increases and decreases during the different seasons into the components that occur in the vicinity or at larger distance from the different weather events. Preliminary results indicate that the amplitude of both positive and negative sea ice changes increases around cyclones, with an overall net effect of reducing sea-ice concentration during most seasons. Thus, the effect of the wind and warm intrusions within cyclones dominates over the effect of the cyclone’s cold sector. In contrast, cold-air outbreaks are associated with sea-ice growth at any time of the year, but exhibit a clear seasonality in their frequency of occurrence.

The distinction between eddy-driven and subtropical jets is conceptually important and well-founded through different driving mechanisms and dominant types of variability. Despite this clear conceptual distinction between the jet types, it is not straightforward to distinguish between these jet archetypes in reanalysis data of individually detected jets.Inspired by EOF and cluster analyses exploring the variablity between different jets, we here propose a novel and easy-to-apply criterion to distinguish between subtropical and eddy-driven jets. We document that for most ocean basins and seasons, there is a clear bimodality in the occurrence of jets in a potential temperature/wind speed space. These two jet modes in this phase space align well with the conceptual expectations for subtropical and eddy-driven jets regarding their vertical structure as well as their regional and seasonal occurrence.Surprisingly, the bimodality in phase space is most pronounced in regions such as the western North Pacific during winter, where jets are typically regarded as “merged”, a mixture of eddy-driven and subtropical. Our results thus call into question this typical intepretation of the Pacific jet, and rather suggest that the Pacific winter jet becomes more “merged” in character towards the eastern end of the storm track.

Cyclone clustering, the succession of multiple extratropical cyclones during a short period of time, has a huge impact on European weather extremes. The idea that several cyclones follow a similar track already dates back to the concept of cyclone families of Bjerknes and Solberg. To investigate the dynamical causes of cyclone clustering, one needs to diagnose where cyclone clustering occurs and determine their characteristics. So far most diagnostics either focused on either local impact-based diagnostics or on a statistical analysis of storm recurrence. While the first cannot be applied globally, the latter is difficult to relate to individual events. We therefore present a new way to globally detect cyclone clustering that is closer to the original concept of Bjerknes and Solberg that extratropical cyclones follow similar tracks.Using this new cyclone clustering diagnostic based on spatio-temporal distance between cyclone tracks, we analyse cyclone clustering globally in Era-Interim for the period 1979 until 2016. We complement this analysis with a baroclinicity diagnostic based on the slope of isentropic surfaces. With the isentropic slope and its tendencies, the relative role of diabatic and adiabatic effects associated with extra-tropical cyclones in maintaining baroclinicity are assessed. We find that cyclone clustering mainly occurs along the climatological storm tracks. In general, clustered cyclones are stronger than non-clustered cyclones. Moreover clustered cyclones are more often related to atmospheric rivers and stronger isentropic slope, indicating that diabatic effects might be an important mechanism in the formation of cyclone clustering.

Precipitation has increased globally in the mean during the past century and is expected to continue to increase with rising temperatures. In the mid- to high latitudes, extratropical cyclones, fronts, atmospheric rivers, and cold air outbreaks are associated with a substantial fraction of the total precipitation. As these weather features might respond differently to a changing climate, investigating precipitation changes in the context of weather systems provides further insight into the observed changes in precipitation. Therefore, we introduce a new method for attributing precipitation to weather features. The method allows us to decompose total precipitation into the respective contributions by extratropical cyclones, fronts, atmospheric rivers, cold air outbreaks, and their combinations.We have classified precipitation between 1930-2010 in the ECMWF’s twentieth century reanalyses project, ERA-20C. Our method assigns 70% of the total precipitation poleward of 30° to the aforementioned categories, allowing us to assess the relative importance of these weather features for total precipitation and for precipitation extremes. We find that the combination of extratropical cyclones, fronts, and atmospheric rivers accounts for more than 50% of the total precipitation and for 90% of the extreme events in the northern hemisphere storm-track regions, despite these precipitation events occurring less than 20% of the time.