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Tides are proved to have a significant effect on the ocean and climate. Previous modelling research either adds a tidal mixing parameterisation or an explicit tidal forcing to the ocean models. However, no research compares the two approaches in the same framework. Here we implement both schemes in a general ocean circulation model and assess both methods by comparing the results. The aspects for comparison involve hydrography, sea ice, meridional overturning circulation (MOC), vertical diffusivity, barotropic streamfunction and energy diagnostics. We conclude that although the mesh resolution is poor in resolving internal tides in most mid-latitude and shelf-break areas, explicit tidal forcing still shows stronger tidal mixing at the Kuril–Aleutian Ridge and the Indonesian Archipelago than the tidal mixing parameterisation. Beyond that, the explicit tidal forcing method leads to a stronger upper cell of the Atlantic MOC by enhancing the Pacific MOC and the Indonesian Throughflow. Meanwhile, the tidal mixing parameterisation leads to a stronger lower cell of the Atlantic MOC due to the tidal mixing in deep oceans. Both methods maintain the Antarctic Circumpolar Current at a higher level than the control run by increasing the meridional density gradient. We also show several phenomena that are not considered in the tidal mixing parameterisation, for example, the changing of energy budgets in the ocean system, the bottom drag induced mixing on the continental shelves and the sea ice transport by tidal motions. Due to the limit of computational capacity, an internal-tide-resolving simulation is not feasible for climate studies. However, a high-resolution short-term tidal simulation is still required to improve parameters and parameterisation schemes in climate studies.

Due to the increasing internationalization of markets, rising cost pressure, and shortened product life cycles, manufacturing companies are facing increasing competition and innovation pressure. To secure competitiveness, the early development of new and innovative technologies and their implementation in the market as products or services is paramount. To use available resources for innovation efficiently, potentials of new technologies must be exploited at early stages. The main objective of this paper is to support companies in early decision-making processes regarding new technologies by providing a systematic approach to technology assessment. For this purpose, a model is developed which supports the evaluation of the technology potentials based on the limited information available at an early stage and, thus, creates the basis for an initial technology selection.

We developed a new version of the Alfred Wegener Institute Climate Model (AWI-CM3), which has higher skills in representing the observed climatology and better computational efficiency than its predecessors. Its ocean component FESOM2 has the multi-resolution functionality typical for unstructured-mesh models while still featuring a scalability and efficiency similar to regular-grid models. The atmospheric component OpenIFS (CY43R3) enables the use of latest developments in the numerical weather prediction community in climate sciences. In this paper we describe the coupling of the model components and evaluate the model performance on a variable resolution (25–125 km) ocean mesh and a 61 km atmosphere grid, which serves as a reference and starting point for other on-going research activities with AWI-CM3. This includes the exploration of high and variable resolution, the development of a full Earth System Model as well as the creation of a new sea ice prediction system. At this early development stage and with the given coarse to medium resolutions, the model already features above CMIP6-average skills in representing the climatology and competitive model throughput. Finally we identify remaining biases and suggest further improvements to be made to the model.

Study region Europe, with a particular focus on the Czech Republic, Poland, Spain, and Norway. Study focus Long-lasting droughts have become a semi-permanent feature of the European climate, especially over the last two decades. These prolonged droughts are usually driven by persistent sea surface temperature anomalies over the Pacific and Atlantic basins. By employing complex statistical methods (i.e., Canonical Correlation Analysis and Convergent Cross-Mapping) in this study we make a comprehensive assessment of the observed drying trend over the central and southern parts of Europe and its underlying drivers. New hydrological insights Building upon the potential relationship between drought variability and large-scale oceanic and atmospheric circulation, we show that the observed drying trend in the central and southern parts of Europe has been driven by a long-term slowdown of the Atlantic Meridional Overturning Circulation (AMOC), via changes in the large-scale atmospheric circulation. A weakening of AMOC leads to an increase in the frequency of atmospheric-blocking like circulation over the central part of Europe, which in turn inhibits precipitation and favors long-term drying. Since climate projections indicate a slowdown of the AMOC in the future, we suggest that this will potentially lead to an increase in the frequency of dry years, especially over the central and southern parts of Europe (e.g., the eastern part of Germany, the Czech Republic, Poland, Spain and Portugal).

The second part of the assessment and evaluation of the unstructured-mesh Finite-volumE Sea ice–Ocean Model version 2.0 (FESOM2.0) is presented. It focuses on the performance of partial cells and embedded sea ice and the effect of mixing parameterisations available through the Community Vertical Mixing (CVMix) package. It is shown that partial cells and embedded sea ice lead to significant improvements in the representation of the Gulf Stream and North Atlantic Current and the circulation of the Arctic Ocean. In addition to the already existing Pacanowski and Phillander (fesom_PP) and K-profile (fesom_KPP) parameterisations for vertical mixing in FESOM2.0, we document the impact of several mixing parameterisations from the CVMix project library. Among them are the CVMix versions of Pacanowski and Phillander (cvmix_PP) and K-profile (cvmix_KPP) parameterisations; the tidal mixing parameterisation (cvmix_TIDAL); a vertical mixing parameterisation based on turbulent kinetic energy (cvmix_TKE); and a combination of cvmix_TKE and the recent scheme for the computation of the Internal Wave Dissipation, Energy, and Mixing (IDEMIX) parameterisation. IDEMIX parameterises the redistribution of internal wave energy through wave propagation, non-linear interactions and the associated imprint on the vertical background diffusivity. Further, the benefit from using a parameterisation of Southern Hemisphere sea ice melt season mixing in the surface layer (MOMIX) for reducing Southern Ocean hydrographic biases in FESOM2.0 is presented. We document the implementation of different model components and illustrate their behaviour. This paper serves primarily as a reference for FESOM users but is also useful to the broader modelling community.

Using the depth (z) and density (ϱ) frameworks, we analyze local contributions to AMOC variability in a 900-year simulation with the AWI climate model. Both frameworks reveal a consistent interdecadal variability; however, the correlation between their maxima deteriorates on year-to-year scales. We demonstrate the utility of analyzing the spatial patterns of sinking and diapycnal transformations through depth levels and isopycnals. The success of this analysis relies on the spatial binning of these maps which is especially crucial for the maps of vertical velocities which appear to be too noisy in the main regions of up- and downwelling because of stepwise bottom topography. Furthermore, we show that the AMOC responds to fast (annual or faster) fluctuations in atmospheric forcing associated with the NAO. This response is more obvious in the ϱ than in the z framework. In contrast, the link between AMOC deep water production south of Greenland is found for slower fluctuations and is consistent between the frameworks.

Megadroughts are notable manifestations of the American Southwest, but not so much of the European climate. By using long-term hydrological and meteorological observations, as well as paleoclimate reconstructions, here we show that central Europe has experienced much longer and severe droughts during the Spörer Minimum (~AD 1400–1480) and Dalton Minimum (~AD 1770–1840), than the ones observed during the 21st century. These two megadroughts appear to be linked with a cold state of the North Atlantic Ocean and enhanced winter atmospheric blocking activity over the British Isles and western part of Europe, concurrent with reduced solar forcing and explosive volcanism. Moreover, we show that the recent drought events (e.g., 2003, 2015, and 2018), are within the range of natural variability and they are not unprecedented over the last millennium.

In the face of the increasing internationalization of markets, rising cost pressure, and shorter product life cycles, manufacturing companies are facing increasing competition and innovation pressure. To secure competitiveness, the early development of new and innovative technologies and their implementation on the market as products or services is paramount. However, besides high potential benefits, new technologies are also associated with high risks regarding their technological feasibility as well as their estimated economic implications. Existing approaches of technology assessment usually focus on evaluating the technological potential, while the risks associated with these technologies are hardly considered. However, existing risks influence the probability of realizing the predicted technology potentials, making an exclusive assessment of the technological potentials by no means sufficient for an adequate evaluation of new technologies. Hence, the consideration of potential risks is of particular importance for the initial assessment and selection of technologies at an early stage. To promote the consideration of risks in technology assessment from a holistic perspective, this paper identifies both technological and economic risk factors of new technologies based on a systematic literature review.

We propose to make the damping time scale, which governs the decay of pseudo-elastic waves in the Elastic Viscous Plastic (EVP) sea-ice solvers, independent of the external time step and large enough to warrant numerical stability for a moderate number of internal time steps. A necessary condition is that the forcing on sea ice varies slowly on the damping time scale, in which case an EVP solution may still approach a Viscous Plastic one, but on a time scale longer than a single external time step. In this case, the EVP method becomes very close to the recently proposed modified EVP (mEVP) method in terms of stability and simulated behavior. In a simple test case dealing with sea ice breaking under the forcing of a moving cyclone, the EVP method with an enlarged damping time scale can simulate linear kinematic features which are very similar to those from the traditional EVP implementation, although a much smaller number of internal time steps is used. There is more difference in sea-ice thickness and linear kinematic features simulated in a realistic Arctic configuration between using the traditional and our suggested choices of EVP damping time scales, but it is minor considering model uncertainties associated with choices of many other parameters in sea-ice models.