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  • 2020-2022  (399,843)
  • 2021  (399,843)
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  • 1
    Publication Date: 2021-12-29
    Description: Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. This report, on methods for supporting stock assessment in the Mediterranean (STECF-21-02), addresses the data checking and preparation for stock assessment once the data has been submitted following the annual data calls. The report provides an overview of the data errors and quality control carried out on both commercial landings data and MEDITS survey data. The analyses reported also address the small fraction of commercial catch with sampling gaps, and how these are assigned appropriate length frequency distributions. The results of these check and assignments are provided by species, GSA and country. Quality checks were carried out on Medits data check consistency of the main reporting files and highlighting where data inconsistencies occurred. Additionally the total landings reported to the European Commission under the Black & Med-Sea data call, the Fisheries Independent Data call and the Annual Economic Report data call were compared at species aggregated to GSA. Some important differences were observed and these are reported. In addition the EWG reviewed a technical report on the sampling of commercial catch in the Greek Fisheries, the review and some suggested further work are included in this report.
    Description: European Union, Joint Research Centre
    Description: Published
    Description: Refereed
    Keywords: Stock assessment ; Fisheries management
    Repository Name: AquaDocs
    Type: Report
    Format: 1269pp.
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  • 2
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    In:  EPIC3EGU General Assembly 2021, online, 2021-04-19-2021-04-30
    Publication Date: 2021-12-28
    Description: Based on the shallow water equations,the tsunami wave propagation in the deep ocean and an assessment of the wave height at the coast can easily be simulated online during an event. To simulate the estimated inundation, however, poses higher demands on model physics and mesh resolution. Whereas in the deep ocean, a simple balance between pressure gradient force and acceleration is sufficient for first estimates of the wave propagation, additional nonlinear factors like bottom friction and momentum advection gain importance close to the coast. For a seamless simulation of the transition from wave propagation to inundation, the finite element model TsunAWI has been developed as part of the efforts within the GITEWS project (German Indonesian Tsunami Early Warning System) and in the meantime, the code has evolved considerably with applications in several projects. The triangular mesh approach allows for large freedom in the resolution of coastline and bathymetric features, however is also numerically demanding. In the ongoing EU-project LEXIS (Large-scale Execution for Industry & Society), the simulation of earthquake and tsunami events is one of the pilot study cases and on the tsunami side puts focus on the optimization of TsunAWI on modern HPC architectures. Targeting FPGAs, an accelerator for TsunAWI is being designed. It relies on a software-distributed shared memory (S-DSM) allowing sharing of the memory between distributed nodes and the accelerator(s), and is showing that TsunAWI optimisations, namely single precision and unstructured mesh traversal, are key elements to reach high performance and efficiency. For HPC systems, an MPI parallelization was implemented, based on domain decomposition. The MPI parallel code shows good scaling, making high resolution simulations feasible during an event. The developments are evaluated in simulations of tsunami inundation in hypothetical and real events in Indonesia and Chile. It turns out that the optimized approach allows for improved fast estimates of the tsunami impact in the application cases.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    In:  EPIC3Workshop: Multi-annual to Decadal Climate Predictability in the North Atlantic-Arctic Sector, Online, September 20-22, 2021
    Publication Date: 2021-12-28
    Description: The Parallel Data Assimilation Framework (PDAF, http://pdaf.awi.de) is an open-source software framework for highly efficient ensemble data assimilation with complex models on supercomputers. PDAF was developed to simplify the generation of a data assimilation system from existing models. For coupled data assimilation, PDAF is used for example with the coupled atmosphere-ocean model AWI-CM, with different coupled ocean biogeochemical models, and with the atmosphere-land surface-subsurface model TerrSysMP. However, there is a wide range of further applications of PDAF. PDAF provides functionality to perform ensemble integrations, which can be used for ensemble predictions and ensemble data assimilation. Further, PDAF provides several fully-implemented ensemble filter and smoother methods for data assimilation. One can build the data assimilation application either by using model restart files or by directly augmenting the different compartment models of a coupled system with data assimilation functionality. The ensemble data assimilation can then be applied in an efficient way with complex models like AWI-CM on supercomputers with excellent scalability and efficiency. PDAF directly supports both weakly and strongly coupled data assimilation. Discussed will be the features of PDAF and the structure of data assimilation systems for coupled data assimilation with PDAF.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    In:  EPIC3WCRP-WWRP Symposium on Data Assimilation and Reanalysis, online, September 13-18, 2021
    Publication Date: 2021-12-28
    Description: PDAF, the Parallel Data Assimilation Framework (http://pdaf.awi.de), is an open-source framework for ensemble data assimilation (DA). PDAF is designed to be particularly easy to use and a DA system can be quickly build, while PDAF ensures the computational efficiency. PDAF's ensemble-component provides online-coupled DA functionality, thus data transfers in memory and by using the MPI parallelization standard, by inserting 3 function calls into the model code. These additions convert a numerical model into a data-assimilative model, which can be run like the original model, but with additional options. Alternatively, one can use separate programs to compute the forecasts and the DA analysis update. PDAF further provides DA methods (solvers), in particular ensemble Kalman filters and particle filters. Tools for diagnostics, ensemble generation, and for generating synthetic observations for OSSEs or twin experiments, provide additional functionality for DA. PDAF is used for research purposes, teaching, but also operationally. In the operational context, PDAF is e.g. used at the CMEMS marine forecasting center for the Baltic Sea and in the Chinese Global Ocean Forecasting System (CGOFS). A recent addition to PDAF is OMI, the Observation Module Infrastructure, a library extension for observation handling. OMI is inspired by object-oriented programming, but for ease of use, it is not coded using classes. Recent developments further include support for strongly-coupled DA across components of Earth system models, model bindings for NEMO, SCHISM, and the climate model AWI-CM and ensemble-variational solvers. This presentation discusses the PDAF's features and recent infrastructure developments in PDAF.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev , info:eu-repo/semantics/conferenceObject
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  • 5
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    In:  EPIC3Joint ECMWF/OceanPredict workshop on Advances in Ocean Data Assimilation, online, May 17-20, 2021
    Publication Date: 2021-12-28
    Description: The second-order exact particle filter NETF (nonlinear ensemble transform filter) is combined with local ensemble transform Kalman filter (LETKF) to build a hybrid filter method (LKNETF). The filter combines the stability of the LETKF with the nonlinear properties of the NETF to obtain improved assimilation results for small ensemble sizes. Both filter components are localized in a consistent way so that the filter can be applied with high-dimensional models. The degree of filter nonlinearity is defined by a hybrid weight, which shifts the analysis between the LETKF and NETF. Since the NETF is more sensitive to sampling errors than the LETKF, the latter filter should be preferred in linear cases. It is discussed how an adaptive hybrid weight can be defined based on the nonlinearity of the system so that the adaptivity yields a good filter performance in linear and nonlinear situations. The filter behavior is exemplified based on experiments with the chaotic Lorenz-96 model, in which the nonlinearity can be controlled by the length of the forecast phase, and an idealized configuration of the ocean model NEMO.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev , info:eu-repo/semantics/conferenceObject
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  • 6
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    In:  EPIC3BOOS Annual Meeting, online, November 25, 2021
    Publication Date: 2021-12-28
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev , info:eu-repo/semantics/conferenceObject
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  • 7
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    In:  EPIC3WCRP-WWRP Symposium on Data Assimilation and Reanalysis, online, September 13-18, 2021
    Publication Date: 2021-12-28
    Description: A hybrid nonlinear-Kalman ensemble transform filter (LKNETF) algorithm is build by combining the second-order exact particle filter NETF (nonlinear ensemble transform filter) with the local ensemble transform Kalman filter (LETKF). The hybrid filter combines the stability of the LETKF with the nonlinear properties of the NETF to obtain improved assimilation results for small ensemble sizes. Both filter components are localized in a consistent way so that the filter can be applied with high-dimensional models. The degree of filter nonlinearity is defined by a hybrid weight, which shifts the analysis between the LETKF and NETF. Since the NETF is more sensitive to sampling errors than the LETKF, the latter filter should be preferred in linear Gaussian cases. An adaptive hybrid weight can be defined based on the nonlinearity of the system so that the adaptivity yields a good filter performance in both linear and nonlinear situations. In particular the skewness and kurtosis of the ensemble can be applied to quantify the non-Gaussianity. The filter behavior is exemplified based on experiments with the chaotic Lorenz-63 und -96 models, in which the nonlinearity can be controlled by the length of the forecast phase. In these experiments the hybrid filter can yield an error reduction of up to 28% compared to the LETKF.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
    Publication Date: 2021-12-28
    Description: We compare strongly coupled data assimilation (SCDA) and weakly coupled data assimilation (WCDA) by analyzing the assimilation effect on the estimation of the ocean and the atmosphere variables. The AWI climate model (AWI-CM-1.1) is coupled with the parallel data assimilation framework (PDAF). Only satellite sea surface temperature data are assimilated. For WCDA, only the ocean variables are directly updated by the assimilation. For SCDA, both the ocean and the atmosphere variables are directly updated by the assimilation. Both WCDA and SCDA improve ocean state and yield similar errors. In the atmosphere, WCDA gives slightly smaller errors for the near-surface temperature and wind velocity than SCDA. In the free atmosphere, SCDA yields smaller errors for the temperature, wind velocity, and specific humidity than WCDA in the Arctic region, while in the tropical region, the errors are generally larger.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2021-12-28
    Description: To improve Antarctic sea-ice simulations and estimations, an ensemble-based Data Assimilation System for the Southern Ocean (DASSO) was developed based on a regional sea ice–ocean coupled model, which assimilates sea-ice thickness (SIT) together with sea-ice concentration (SIC) derived from satellites. To validate the performance of DASSO, experiments were conducted from 15 April to 14 October 2016. Generally, assimilating SIC and SIT can suppress the overestimation of sea ice in the model-free run. Besides considering uncertainties in the operational atmospheric forcing data, a covariance inflation procedure in data assimilation further improves the simulation of Antarctic sea ice, especially SIT. The results demonstrate the effectiveness of assimilating sea-ice observations in reconstructing the state of Antarctic sea ice, but also highlight the necessity of more reasonable error estimation for the background as well as the observation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    In:  EPIC3APECS-ARICE Tech Training
    Publication Date: 2021-12-27
    Repository Name: EPIC Alfred Wegener Institut
    Type: Miscellaneous , notRev
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