المؤلفون: S. Danilov, S. Juricke, K. Nowak, D. Sidorenko, Q. Wang

المصدر: Journal of Advances in Modeling Earth Systems, Vol 16, Iss 5, Pp n/a-n/a (2024)

مصطلحات موضوعية: unstructured meshes, coarse graining, energy spectra, implicit filters, Physical geography, GB3-5030, Oceanography, GC1-1581

الوصف: Abstract Scale analysis based on coarse‐graining has been proposed recently as an alternative to Fourier analysis. It requires interpolation to a regular mesh for data from unstructured‐mesh models. We propose an alternative coarse‐graining method which relies on implicit filters using powers of discrete Laplacians. This method can work on arbitrary (structured or unstructured) meshes and is applicable to the direct output of unstructured‐mesh models. Illustrations and detailed discussions are provided for discrete fields placed at vertices of triangular meshes. The case with placement on triangles is also briefly discussed.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1942-2466Test

الوصول الحر: https://doaj.org/article/9369c1db7ae04fb4a0f852188984d638Test

المؤلفون: N. Stoll, M. Wietz, S. Juricke, F. Pausch, C. Peter, M. Seifert, J. C. Massing, M. Zeising, R. A. McPherson, M. Käß, B. Suckow

المصدر: Polarforschung, Vol 91, Pp 31-43 (2023)

مصطلحات موضوعية: Environmental sciences, GE1-350

الوصف: Science communication is becoming increasingly important to connect academia and society and to counteract misinformation. Online video platforms, such as YouTube, allow easily accessible communication of scientific knowledge to audiences made up of the general public. In April 2020, a diverse group of researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, launched the YouTube channel called “Wissenschaft fürs Wohnzimmer” (translated to “Living Room Science”) to stream scientific talks about climate change and biodiversity every Thursday evening, with the aim to reach a broad range of members of the public with a general interest in science and climate. Here we report on the numbers and diversity of content, viewers, and presenters from 2 years and 100 episodes of weekly livestreams. Presented topics encompass all areas of polar research, the scientific and societal aspects of climate change and biodiversity loss, and new technologies to deal with the changing world and climate of the future. We show that constant engagement by a group of co-hosts and presenters representing all topics, career stages, and genders enables the continuous growth of views and subscriptions, i.e. a measurable impact. After 783 d, the channel gained 30 251 views and 828 subscribers and hosted well-known scientists, while enabling especially early-career researchers to foster their outreach and media skills. We show that interactive and science-related videos, both live and on-demand, within a pleasant atmosphere, can be produced alongside the main research activity by scientists, while also maintaining high quality. We further discuss the challenges and possible improvements for the future. Our experiences will help other researchers conduct meaningful scientific outreach and push the boundaries of existing formats towards a better understanding of climate change and our planet.

وصف الملف: electronic resource

العلاقة: https://polf.copernicus.org/articles/91/31/2023/polf-91-31-2023.pdfTest; https://doaj.org/toc/0032-2490Test; https://doaj.org/toc/2190-1090Test

الوصول الحر: https://doaj.org/article/a7d160e15cec46fa96386efd6f056869Test

المؤلفون: K. Strommen, S. Juricke, F. Cooper

المصدر: Weather and Climate Dynamics, Vol 3, Pp 951-975 (2022)

مصطلحات موضوعية: Meteorology. Climatology, QC851-999

الوصف: The extent to which interannual variability in Arctic sea ice influences the mid-latitude circulation has been extensively debated. While observational data support the existence of a teleconnection between November sea ice in the Barents–Kara region and the subsequent winter North Atlantic Oscillation, climate models do not consistently reproduce such a link, with only very weak inter-model consensus. We show, using the EC-Earth3 climate model, that while an ensemble of coupled EC-Earth3 simulations shows no evidence of such a teleconnection, the inclusion of stochastic parameterizations to the ocean and sea ice component results in the emergence of a robust teleconnection comparable in magnitude to that observed. While the exact mechanisms causing this remain unclear, we argue that it can be accounted for by an improved ice–ocean–atmosphere coupling due to the stochastic perturbations, which aim to represent the effect of unresolved ice and ocean variability. In particular, the weak inter-model consensus may to a large extent be due to model biases in surface coupling, with stochastic parameterizations being one possible remedy.

وصف الملف: electronic resource

العلاقة: https://wcd.copernicus.org/articles/3/951/2022/wcd-3-951-2022.pdfTest; https://doaj.org/toc/2698-4016Test

الوصول الحر: https://doaj.org/article/e80de4ca085e4309b16f08426e72a3c9Test

المؤلفون: J. Streffing, D. Sidorenko, T. Semmler, L. Zampieri, P. Scholz, M. Andrés-Martínez, N. Koldunov, T. Rackow, J. Kjellsson, H. Goessling, M. Athanase, Q. Wang, J. Hegewald, D. V. Sein, L. Mu, U. Fladrich, D. Barbi, P. Gierz, S. Danilov, S. Juricke, G. Lohmann, T. Jung

المصدر: Geoscientific Model Development, Vol 15, Pp 6399-6427 (2022)

مصطلحات موضوعية: Geology, QE1-996.5

الوصف: 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 (Finite-volumE Sea ice–Ocean Model) has the multi-resolution functionality typical of unstructured-mesh models while still featuring a scalability and efficiency similar to regular-grid models. The atmospheric component OpenIFS (CY43R3) enables the use of the 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 ongoing research activities with AWI-CM3. This includes the exploration of high and variable resolution and 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 (where CMIP6 denotes Coupled Model Intercomparison Project phase 6) in representing the climatology and competitive model throughput. Finally we identify remaining biases and suggest further improvements to be made to the model.

وصف الملف: electronic resource

العلاقة: https://gmd.copernicus.org/articles/15/6399/2022/gmd-15-6399-2022.pdfTest; https://doaj.org/toc/1991-959XTest; https://doaj.org/toc/1991-9603Test

الوصول الحر: https://doaj.org/article/f1e6a53884b64b379b7096a1be22c2c9Test

المؤلفون: S. Juricke, K. Bellinghausen, S. Danilov, A. Kutsenko, M. Oliver

المصدر: Journal of Advances in Modeling Earth Systems, Vol 15, Iss 1, Pp n/a-n/a (2023)

مصطلحات موضوعية: spectral analysis, scale analysis, momentum closure, kinetic energy spectra, dissipation power spectra, unstructured grids, Physical geography, GB3-5030, Oceanography, GC1-1581

الوصف: Abstract Fourier spectra are powerful tools to analyze the scale behavior of turbulent flows. While such spectra are mathematically based on regular periodic data, some state‐of‐the‐art ocean and climate models use unstructured triangular meshes. Observational data is often also available only in an unstructured fashion. In this study, scale analysis specifically for the output of models with triangular meshes is discussed and the representable wavenumbers for Fourier analysis are derived. Aside from using different interpolation methods and oversampling prior to the computation of Fourier spectra, we also consider an alternative scale analysis based on the Walsh–Rademacher basis, that is, indicator functions. It does not require interpolation and can be extended to general unstructured meshes. A third approach based on smoothing filters which focus on grid scales is also discussed. We compare these methods in the context of kinetic energy and dissipation power of a turbulent channel flow simulated with the sea ice‐ocean model FESOM2. One simulation uses a classical viscous closure, another a new backscatter closure. The latter is dissipative on small scales, but anti‐dissipative on large scales leading to more realistic flow representation. All three methods clearly highlight the differences between the simulations as concerns the distribution of dissipation power and kinetic energy over scales. However, the analysis based on Fourier transformation is highly sensitive to the interpolation method in case of dissipation power, potentially leading to inaccurate representations of dissipation at different scales. This highlights the necessity to be cautious when choosing a scale analysis method on unstructured grids.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1942-2466Test

الوصول الحر: https://doaj.org/article/516eb4d8001149f6a7e0838a2071923bTest

المؤلفون: D. Sidorenko, H.F. Goessling, N.V. Koldunov, P. Scholz, S. Danilov, D. Barbi, W. Cabos, O. Gurses, S. Harig, C. Hinrichs, S. Juricke, G. Lohmann, M. Losch, L. Mu, T. Rackow, N. Rakowsky, D. Sein, T. Semmler, X. Shi, C. Stepanek, J. Streffing, Q. Wang, C. Wekerle, H. Yang, T. Jung

المصدر: Journal of Advances in Modeling Earth Systems, Vol 11, Iss 11, Pp 3794-3815 (2019)

مصطلحات موضوعية: FESOM, ocean model, climate model, unstructured mesh, Finite Volume, Physical geography, GB3-5030, Oceanography, GC1-1581

الوصف: Abstract A new global climate model setup using FESOM2.0 for the sea ice‐ocean component and ECHAM6.3 for the atmosphere and land surface has been developed. Replacing FESOM1.4 by FESOM2.0 promises a higher efficiency of the new climate setup compared to its predecessor. The new setup allows for long‐term climate integrations using a locally eddy‐resolving ocean. Here it is evaluated in terms of (1) the mean state and long‐term drift under preindustrial climate conditions, (2) the fidelity in simulating the historical warming, and (3) differences between coarse and eddy‐resolving ocean configurations. The results show that the realism of the new climate setup is overall within the range of existing models. In terms of oceanic temperatures, the historical warming signal is of smaller amplitude than the model drift in case of a relatively short spin‐up. However, it is argued that the strategy of “de‐drifting” climate runs after the short spin‐up, proposed by the HighResMIP protocol, allows one to isolate the warming signal. Moreover, the eddy‐permitting/resolving ocean setup shows notable improvements regarding the simulation of oceanic surface temperatures, in particular in the Southern Ocean.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1942-2466Test

الوصول الحر: https://doaj.org/article/788031fb96614560af7484ebb868377dTest

المؤلفون: D. Sidorenko, S. Danilov, J. Streffing, V. Fofonova, H. F. Goessling, P. Scholz, Q. Wang, A. Androsov, W. Cabos, S. Juricke, N. Koldunov, T. Rackow, D. V. Sein, T. Jung

المصدر: Journal of Advances in Modeling Earth Systems, Vol 13, Iss 10, Pp n/a-n/a (2021)

مصطلحات موضوعية: AMOC variability, density framework, climate models, Physical geography, GB3-5030, Oceanography, GC1-1581

الوصف: Abstract 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 upwelling 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 and deep water production south of Greenland is found for slower fluctuations and is consistent between the frameworks.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1942-2466Test

الوصول الحر: https://doaj.org/article/3a840b292a25436d94cfc021fa87c44dTest

المؤلفون: K. Strommen, H. M. Christensen, D. MacLeod, S. Juricke, T. N. Palmer

المصدر: Geoscientific Model Development, Vol 12, Pp 3099-3118 (2019)

مصطلحات موضوعية: Geology, QE1-996.5

الوصف: We introduce and study the impact of three stochastic schemes in the EC-Earth climate model: two atmospheric schemes and one stochastic land scheme. These form the basis for a probabilistic Earth system model in atmosphere-only mode. Stochastic parametrization have become standard in several operational weather-forecasting models, in particular due to their beneficial impact on model spread. In recent years, stochastic schemes in the atmospheric component of a model have been shown to improve aspects important for the models long-term climate, such as El Niño–Southern Oscillation (ENSO), North Atlantic weather regimes, and the Indian monsoon. Stochasticity in the land component has been shown to improve the variability of soil processes and improve the representation of heatwaves over Europe. However, the raw impact of such schemes on the model mean is less well studied. It is shown that the inclusion of all three schemes notably changes the model mean state. While many of the impacts are beneficial, some are too large in amplitude, leading to significant changes in the model's energy budget and atmospheric circulation. This implies that in order to maintain the benefits of stochastic physics without shifting the mean state too far from observations, a full re-tuning of the model will typically be required.

وصف الملف: electronic resource

العلاقة: https://www.geosci-model-dev.net/12/3099/2019/gmd-12-3099-2019.pdfTest; https://doaj.org/toc/1991-959XTest; https://doaj.org/toc/1991-9603Test

الوصول الحر: https://doaj.org/article/f3e938d4ad6b4c1d9f287a12cfab24e4Test

المؤلفون: S. Juricke, S. Danilov, N. Koldunov, M. Oliver, D. V. Sein, D. Sidorenko, Q. Wang

المصدر: Journal of Advances in Modeling Earth Systems, Vol 12, Iss 12, Pp n/a-n/a (2020)

مصطلحات موضوعية: kinetic energy backscatter, viscosity closures, mesoscale eddies, ocean modeling, eddy‐permitting resolution, overdissipation, Physical geography, GB3-5030, Oceanography, GC1-1581

الوصف: Abstract Ocean models at eddy‐permitting resolution are generally overdissipative, damping the intensity of the mesoscale eddy field. To reduce overdissipation, we propose a simplified, kinematic energy backscatter parametrization built into the viscosity operator in conjunction with a new flow‐dependent coefficient of viscosity based on nearest neighbor velocity differences. The new scheme mitigates excessive dissipation of energy and improves global ocean simulations at eddy‐permitting resolution. We find that kinematic backscatter substantially raises simulated eddy kinetic energy, similar to an alternative, previously proposed dynamic backscatter parametrization. While dynamic backscatter is scale‐aware and energetically more consistent, its implementation is more complex. Furthermore, it turns out to be computationally more expensive, as it applies, among other things, an additional prognostic subgrid energy equation. The kinematic backscatter proposed here, by contrast, comes at no additional computational cost, following the principle of simplicity. Our primary focus is the discretization on triangular unstructured meshes with cell placement of velocities (an analog of B‐grids), as employed by the Finite‐volumE Sea ice‐Ocean Model (FESOM2). The kinematic backscatter scheme with the new viscosity coefficient is implemented in FESOM2 and tested in the simplified geometry of a zonally reentrant channel as well as in a global ocean simulation on a 1/4° mesh. This first version of the new kinematic backscatter needs to be tuned to the specific resolution regime of the simulation. However, the tuning relies on a single parameter, emphasizing the overall practicality of the approach.

وصف الملف: electronic resource

العلاقة: https://doaj.org/toc/1942-2466Test

الوصول الحر: https://doaj.org/article/cf765c74416b485482fcceeb2f3717e0Test

المؤلفون: P. Davini, J. von Hardenberg, S. Corti, H. M. Christensen, S. Juricke, A. Subramanian, P. A. G. Watson, A. Weisheimer, T. N. Palmer

المصدر: Geoscientific Model Development, Vol 10, Iss 3, Pp 1383-1402 (2017)

مصطلحات موضوعية: Geology, QE1-996.5

الوصف: The Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project is a comprehensive set of ensemble simulations aimed at evaluating the sensitivity of present and future climate to model resolution and stochastic parameterisation. The EC-Earth Earth system model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different atmospheric horizontal resolutions (from 125 up to 16 km). The project includes more than 120 simulations in both a historical scenario (1979–2008) and a climate change projection (2039–2068), together with coupled transient runs (1850–2100). A total of 20.4 million core hours have been used, made available from a single year grant from PRACE (the Partnership for Advanced Computing in Europe), and close to 1.5 PB of output data have been produced on SuperMUC IBM Petascale System at the Leibniz Supercomputing Centre (LRZ) in Garching, Germany. About 140 TB of post-processed data are stored on the CINECA supercomputing centre archives and are freely accessible to the community thanks to an EUDAT data pilot project. This paper presents the technical and scientific set-up of the experiments, including the details on the forcing used for the simulations performed, defining the SPHINX v1.0 protocol. In addition, an overview of preliminary results is given. An improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increase is observed. It is also shown that including stochastic parameterisation in the low-resolution runs helps to improve some aspects of the tropical climate – specifically the Madden–Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small-scale processes on the large-scale climate variability either explicitly (with high-resolution simulations) or stochastically (in low-resolution simulations).

وصف الملف: electronic resource

العلاقة: http://www.geosci-model-dev.net/10/1383/2017/gmd-10-1383-2017.pdfTest; https://doaj.org/toc/1991-959XTest; https://doaj.org/toc/1991-9603Test

الوصول الحر: https://doaj.org/article/1e85a68837bf40ed8c20a5af8a2604b2Test