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  • 1
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 13, No. 8 ( 2020-08-21), p. 3643-3708
    Kurzfassung: Abstract. We present a new framework for global ocean–sea-ice model simulations based on phase 2 of the Ocean Model Intercomparison Project (OMIP-2), making use of the surface dataset based on the Japanese 55-year atmospheric reanalysis for driving ocean–sea-ice models (JRA55-do). We motivate the use of OMIP-2 over the framework for the first phase of OMIP (OMIP-1), previously referred to as the Coordinated Ocean–ice Reference Experiments (COREs), via the evaluation of OMIP-1 and OMIP-2 simulations from 11 state-of-the-science global ocean–sea-ice models. In the present evaluation, multi-model ensemble means and spreads are calculated separately for the OMIP-1 and OMIP-2 simulations and overall performance is assessed considering metrics commonly used by ocean modelers. Both OMIP-1 and OMIP-2 multi-model ensemble ranges capture observations in more than 80 % of the time and region for most metrics, with the multi-model ensemble spread greatly exceeding the difference between the means of the two datasets. Many features, including some climatologically relevant ocean circulation indices, are very similar between OMIP-1 and OMIP-2 simulations, and yet we could also identify key qualitative improvements in transitioning from OMIP-1 to OMIP-2. For example, the sea surface temperatures of the OMIP-2 simulations reproduce the observed global warming during the 1980s and 1990s, as well as the warming slowdown in the 2000s and the more recent accelerated warming, which were absent in OMIP-1, noting that the last feature is part of the design of OMIP-2 because OMIP-1 forcing stopped in 2009. A negative bias in the sea-ice concentration in summer of both hemispheres in OMIP-1 is significantly reduced in OMIP-2. The overall reproducibility of both seasonal and interannual variations in sea surface temperature and sea surface height (dynamic sea level) is improved in OMIP-2. These improvements represent a new capability of the OMIP-2 framework for evaluating process-level responses using simulation results. Regarding the sensitivity of individual models to the change in forcing, the models show well-ordered responses for the metrics that are directly forced, while they show less organized responses for those that require complex model adjustments. Many of the remaining common model biases may be attributed either to errors in representing important processes in ocean–sea-ice models, some of which are expected to be reduced by using finer horizontal and/or vertical resolutions, or to shared biases and limitations in the atmospheric forcing. In particular, further efforts are warranted to resolve remaining issues in OMIP-2 such as the warm bias in the upper layer, the mismatch between the observed and simulated variability of heat content and thermosteric sea level before 1990s, and the erroneous representation of deep and bottom water formations and circulations. We suggest that such problems can be resolved through collaboration between those developing models (including parameterizations) and forcing datasets. Overall, the present assessment justifies our recommendation that future model development and analysis studies use the OMIP-2 framework.
    Materialart: Online-Ressource
    ISSN: 1991-9603
    Sprache: Englisch
    Verlag: Copernicus GmbH
    Publikationsdatum: 2020
    ZDB Id: 2456725-5
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Journal of Instrumentation, IOP Publishing, Vol. 17, No. 01 ( 2022-01-01), p. P01013-
    Kurzfassung: The semiconductor tracker (SCT) is one of the tracking systems for charged particles in the ATLAS detector. It consists of 4088 silicon strip sensor modules. During Run 2 (2015–2018) the Large Hadron Collider delivered an integrated luminosity of 156 fb -1 to the ATLAS experiment at a centre-of-mass proton-proton collision energy of 13 TeV. The instantaneous luminosity and pile-up conditions were far in excess of those assumed in the original design of the SCT detector. Due to improvements to the data acquisition system, the SCT operated stably throughout Run 2. It was available for 99.9% of the integrated luminosity and achieved a data-quality efficiency of 99.85%. Detailed studies have been made of the leakage current in SCT modules and the evolution of the full depletion voltage, which are used to study the impact of radiation damage to the modules.
    Materialart: Online-Ressource
    ISSN: 1748-0221
    Sprache: Unbekannt
    Verlag: IOP Publishing
    Publikationsdatum: 2022
    ZDB Id: 2235672-1
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    In: JAMA Cardiology, American Medical Association (AMA), Vol. 7, No. 10 ( 2022-10-01), p. 1000-
    Kurzfassung: In patients with severe aortic valve stenosis at intermediate surgical risk, transcatheter aortic valve replacement (TAVR) with a self-expanding supra-annular valve was noninferior to surgery for all-cause mortality or disabling stroke at 2 years. Comparisons of longer-term clinical and hemodynamic outcomes in these patients are limited. Objective To report prespecified secondary 5-year outcomes from the Symptomatic Aortic Stenosis in Intermediate Risk Subjects Who Need Aortic Valve Replacement (SURTAVI) randomized clinical trial. Design, Setting, and Participants SURTAVI is a prospective randomized, unblinded clinical trial. Randomization was stratified by investigational site and need for revascularization determined by the local heart teams. Patients with severe aortic valve stenosis deemed to be at intermediate risk of 30-day surgical mortality were enrolled at 87 centers from June 19, 2012, to June 30, 2016, in Europe and North America. Analysis took place between August and October 2021. Intervention Patients were randomized to TAVR with a self-expanding, supra-annular transcatheter or a surgical bioprosthesis. Main Outcomes and Measures The prespecified secondary end points of death or disabling stroke and other adverse events and hemodynamic findings at 5 years. An independent clinical event committee adjudicated all serious adverse events and an independent echocardiographic core laboratory evaluated all echocardiograms at 5 years. Results A total of 1660 individuals underwent an attempted TAVR (n = 864) or surgical (n = 796) procedure. The mean (SD) age was 79.8 (6.2) years, 724 (43.6%) were female, and the mean (SD) Society of Thoracic Surgery Predicted Risk of Mortality score was 4.5% (1.6%). At 5 years, the rates of death or disabling stroke were similar (TAVR, 31.3% vs surgery, 30.8%; hazard ratio, 1.02 [95% CI, 0.85-1.22]; P  =   .85). Transprosthetic gradients remained lower (mean [SD], 8.6 [5.5] mm Hg vs 11.2 [6.0] mm Hg; P   & amp;lt; .001) and aortic valve areas were higher (mean [SD], 2.2 [0.7] cm 2 vs 1.8 [0.6] cm 2 ; P   & amp;lt; .001) with TAVR vs surgery. More patients had moderate/severe paravalvular leak with TAVR than surgery (11 [3.0%] vs 2 [0.7%] ; risk difference, 2.37% [95% CI, 0.17%- 4.85%]; P  = .05). New pacemaker implantation rates were higher for TAVR than surgery at 5 years (289 [39.1%] vs 94 [15.1%] ; hazard ratio, 3.30 [95% CI, 2.61-4.17]; log-rank P   & amp;lt; .001), as were valve reintervention rates (27 [3.5%] vs 11 [1.9%] ; hazard ratio, 2.21 [95% CI, 1.10-4.45]; log-rank P  = .02), although between 2 and 5 years only 6 patients who underwent TAVR and 7 who underwent surgery required a reintervention. Conclusions and Relevance Among intermediate-risk patients with symptomatic severe aortic stenosis, major clinical outcomes at 5 years were similar for TAVR and surgery. TAVR was associated with superior hemodynamic valve performance but also with more paravalvular leak and valve reinterventions.
    Materialart: Online-Ressource
    ISSN: 2380-6583
    Sprache: Englisch
    Verlag: American Medical Association (AMA)
    Publikationsdatum: 2022
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 12, No. 7 ( 2019-07-29), p. 3329-3355
    Kurzfassung: Abstract. The Agulhas Current, the western boundary current of the South Indian Ocean, has been shown to play an important role in the connectivity between the Indian and Atlantic oceans. The greater Agulhas Current system is highly dominated by mesoscale dynamics. To investigate their influence on the regional and global circulations, a family of high-resolution ocean general circulation model configurations based on the NEMO code has been developed. Horizontal resolution refinement is achieved by embedding “nests” covering the South Atlantic and the western Indian oceans at 1/10∘ (INALT10) and 1/20∘ (INALT20) within global hosts with coarser resolutions. Nests and hosts are connected through two-way interaction, allowing the nests not only to receive boundary conditions from their respective host but also to feed back the impact of regional dynamics onto the global ocean. A double-nested configuration at 1/60∘ resolution (INALT60) has been developed to gain insights into submesoscale processes within the Agulhas Current system. Large-scale measures such as the Drake Passage transport and the strength of the Atlantic meridional overturning circulation are rather robust among the different configurations, indicating the important role of the hosts in providing a consistent embedment of the regionally refined grids into the global circulation. The dynamics of the Agulhas Current system strongly depend on the representation of mesoscale processes. Both the southward-flowing Agulhas Current and the northward-flowing Agulhas Undercurrent increase in strength with increasing resolution towards more realistic values, which suggests the importance of improving mesoscale dynamics as well as bathymetric slopes along this narrow western boundary current regime. The exploration of numerical choices such as lateral boundary conditions and details of the implementation of surface wind stress forcing demonstrates the range of solutions within any given configuration.
    Materialart: Online-Ressource
    ISSN: 1991-9603
    Sprache: Englisch
    Verlag: Copernicus GmbH
    Publikationsdatum: 2019
    ZDB Id: 2456725-5
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Online-Ressource
    Online-Ressource
    American Meteorological Society ; 2019
    In:  Journal of Physical Oceanography Vol. 49, No. 8 ( 2019-08), p. 2075-2094
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 49, No. 8 ( 2019-08), p. 2075-2094
    Kurzfassung: Oceanic eddies are an important component in preconditioning the central Labrador Sea (LS) for deep convection and in restratifying the convected water. This study investigates the different sources and impacts of eddy kinetic energy (EKE) and its temporal variability in the LS with the help of a 52-yr-long hindcast simulation of a 1/20° ocean model. Irminger Rings (IR) are generated in the West Greenland Current (WGC) between 60° and 62°N, mainly affect preconditioning, and limit the northward extent of the convection area. The IR exhibit a seasonal cycle and decadal variations linked to the WGC strength, varying with the circulation of the subpolar gyre. The mean and temporal variations of IR generation can be attributed to changes in deep ocean baroclinic and upper-ocean barotropic instabilities at comparable magnitudes. The main source of EKE and restratification in the central LS are convective eddies (CE). They are generated by baroclinic instabilities near the bottom of the mixed layer during and after convection. The CE have a middepth core and reflect the hydrographic properties of the convected water mass with a distinct minimum in potential vorticity. Their seasonal to decadal variability is tightly connected to the local atmospheric forcing and the associated air–sea heat fluxes. A third class of eddies in the LS are the boundary current eddies shed from the Labrador Current (LC). Since they are mostly confined to the vicinity of the LC, these eddies appear to exert only minor influence on preconditioning and restratification.
    Materialart: Online-Ressource
    ISSN: 0022-3670 , 1520-0485
    Sprache: Unbekannt
    Verlag: American Meteorological Society
    Publikationsdatum: 2019
    ZDB Id: 2042184-9
    ZDB Id: 184162-2
    Standort Signatur Einschränkungen Verfügbarkeit
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