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Determination of Remaining Service Life of Reinforced Concrete Bridge Structures in Corrosive Environments after Load Testing
Published in Eva O.L. Lantsoght, Load Testing of Bridges, 2019
Dimitri V. Val, Mark G. Stewart
Atmosphere-ocean general circulation models (GCMs) are currently the main tool for climate change studies. AOGCMs are numerical models based on differential equations, which describe physical processes in the atmosphere and ocean (and usually land-surface and sea ice as well) and interactions between them. Uncertainties associated with future emission scenarios are usually not quantified and future climate projections are produced separately for individual scenarios (Stewart et al., 2014). Selecting a GCM to be used in an impact assessment is not a trivial task, given the variety of models. The effect of these uncertainties on climate projections can be considerable.Figure 10.7 shows that RCP 4.5 climate projections for temperature and relative humidity vary considerably when six climate models are compared for Sydney in Australia: CSIRO-Mk3.6.0, ACCESS model (Australia), IPSL CM5A-LR (France), MICRO5 (Japan), bcc-csm1–1 (China) and CNRM-CM5 (European Center).
Ocean Hydrodynamics
Published in Victor Raizer, Optical Remote Sensing of Ocean Hydrodynamics, 2019
Mathematical models of the general circulation in oceans (also known as the primitive equations) follow from the classic nonlinear hydrodynamical equations of a rotating fluid with the use of Boussinesq, hydrostatic, incompressibility, turbulent viscosity, and diffusivity approximations; books (Marchuk and Sarkisyan 1988; Kantha and Clayson 2000; Miller 2007) provides detailed analysis of numerical methods and models. Ocean general circulation models (OGCMs) are a particular version of general circulation model (GCM) and a GCM is a type of climate model. The OGCM describes physical and thermodynamical processes in oceans. Namely, OGCM predicts the evolution of ocean horizontal and vertical velocity, temperature, and salinity fields globally over the full depth of the ocean. In physical oceanography, there is a number of OGCMs which are constantly updated and improved. Comprehensive and practical information about currents and circulation in the oceans can be found in the books (Neumann 1968; Pond and Pickard 1983; Teramoto 1993; Griffies 2004; van Aken 2007; Steele et al. 2009; Huang 2010; Samelson 2011; Siedler et al. 2013; Joseph 2014). List of available OGCMs is in the website: https://en.wikipedia.org/wiki/List_of_ocean_circulation_models.
Basic prediction methods in marine sciences
Published in David R. Green, Jeffrey L. Payne, Marine and Coastal Resource Management, 2017
The OGCM is based on physical background and aims at forecasting various oceanic parameters – such as for instance temperature, salinity or sea level – with a given spatial resolution, time perspective and at all depths. Thus, the OGCM performs numerical modelling of spatial and temporal dynamics of oceanic general circulation, at least covering mesoscale motions. Apart from short- and medium-term operational performance of such models, they can be used to simulate long-term scenarios for the oceans, including those that anticipate how global warming impacts various marine parameters. The early development of OGCMs dates back to the 1960s and 1970s, but in fact progress in their formulation and analysis was initiated earlier by Atmospheric General Circulation Models (AGCMs). In the context of ocean modelling, however, it is worth mentioning a seminal paper by Bryan (1969) who formulated key paradigms and discussed algorithmic issues to be used in OGCMs. Following a didactic overview of OGCMs by McWilliams (1996), fundamentals of OGCMs are based on the Navier-Stokes equations on the rotating Earth applied for seawater. Numerous approximations and simplifications are needed for modelling oceanic general circulation, and they are described in detail in the above-mentioned paper as a resulting boundary-value problem is. Key problems in OGCMs are: parameterization, specifying initial and boundary conditions, knowledge about seafloor topography, resolution in time as well as in horizontal and vertical space. Traditionally, equations are solved using the finite-difference approach, with discrete versions of the governing analytical equations. It has been shown in many papers that OGCMs, when properly constrained, reveal a considerable ability to mimic key elements of the global ocean circulation.
Surface currents in operational oceanography: Key applications, mechanisms, and methods
Published in Journal of Operational Oceanography, 2023
Johannes Röhrs, Graig Sutherland, Gus Jeans, Michael Bedington, Ann Kristin Sperrevik, Knut-Frode Dagestad, Yvonne Gusdal, Cecilie Mauritzen, Andrew Dale, Joseph H. LaCasce
Ocean general circulation models (OGCMs) provide continuous fields of ocean currents, temperature and salinity through discretisation of physical laws. These are conservation of momentum, conservation of mass, and the laws of thermodynamics (Griffies 2004; Roed 2018). Discretisation occurs horizontally on a scale of metres to kilometres, and vertically on a scale of centimetres to metres. Figure 6 shows an example of surface currents from an OGCM with 2.4 km horizontal resolution. This resolution permits the existence of baroclinc eddies, though their generation processes are not fully resolved.