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Robert S. Arthur, Katherine A. Lundquist, David J. Wiersema, Jingyi Bao, and Fotini K. Chow

dynamics applications [see the review of Mittal and Iaccarino (2005) , and references therein]. When the IB method is used, the vertical coordinate is not required to conform to the terrain. Rather, the terrain is represented by an immersed surface that intersects the model grid arbitrarily. Boundary conditions are then applied along the immersed surface by modifying the governing equations in the boundary region. IB methods have recently been used to study environmental flows ( Tseng and Ferziger

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Ron McTaggart-Cowan, Claude Girard, André Plante, and Michel Desgagné

-step reduction required for reliable simulation of the stratospheric jets. Using a nesting technique similar to that employed at the lateral boundaries, this study shows that it is possible for LAM applications to benefit from the enhanced predictability associated with well-represented interactions between the stratosphere and troposphere, resulting in improved numerical guidance under certain flow conditions. The troposphere has long been treated as a wave generator for numerical studies of stratospheric

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Ruth Cerezo-Mota, Myles Allen, and Richard Jones

situation. However, owing to the lack of observations it is very difficult to determine the fidelity of such models or that of the boundary conditions from general circulation models (GCMs) used to drive the regional models. The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) recognized that current GCMs have systematic biases, especially in the simulation of regional features in areas with complex terrain such as the NAM region ( Cavazos and Marengo 2009

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Peter C. Chu, Chenwu Fan, and Laura L. Ehret

observations take place, the solutions are S 1 , S 2 , . . . , S m , which form a solution vector b. Optimization method for determining B Ocean model performance can be measured by the rms error The vector S depends on B. Change of the boundary vector B (boundary conditions) leads to a change of S (solutions). Inversely, we may determine B by minimizing I ; Substitution of (5) into (6) leads to a set of n equations implicitly solvable for b 1 , b 2 , . . . , b

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A. Colin de Verdière, M. Ben Jelloul, and F. Sévellec

-flop oscillations found by Welander with external parameters (such as the values of the variables in the reservoirs of Welander’s model) kept to a minimum. The simplest addition that comes to mind was to add two deep boxes to the Stommel model. Such a 2 × 2 model shows the collapse phase of the THC when the salinity forcing is strong enough but remains in that collapsed “haline mode” under constant boundary conditions. Whatever the initial and forcing conditions, no oscillatory states were ever found. The

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Roger Temam and Joseph Tribbia

equations consist of the laws of conservation of horizontal momentum with minor geometrical approximations, but assume that the vertical pressure gradient is in exact hydrostatic balance with the buoyancy force per unit mass. The analysis of Oliger and Sundström shows that the lateral boundary conditions that are not applied mode by mode must either overdetermine some modes or underdetermine the others. In most numerical models, the boundary conditions are applied pointwise in the vertical leading to

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Vasubandhu Misra

that complex topography and coastline features have a strong impact on the reproducibility of small-scale climate features that a RCM can resolve. But, with the growing use of RCMs it is also becoming apparent that the RCM integrations are limited by the errors in forcing from the lateral boundary conditions (LBCs; Risbey and Stone 1996 ; Noguer et al. 1998 ; Christensen et al. 1998 ; Menendez et al. 2001 ; Misra et al. 2003 ). Furthermore, Christensen et al. (1998) indicate that the

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Edwin K. Schneider and Meizhu Fan

used in section 4 . In particular, the atmospheric feedbacks to the surface evolution need to include the AGCM ensemble response to the evolution of the land surface and sea ice boundary conditions. Weather noise forcing in the interactive ensemble needs to be included over land and sea ice. Although the quantitative importance of these extensions on the determination of the weather noise over the oceans and the subsequent interactive ensemble SST reconstruction is not known, the land

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Giuseppe Zappa, Valerio Lucarini, and Antonio Navarra

their properties. A low-frequency wavenumber 5 had been previously observed by Hendon and Hartmann (1985 , hereafter HH ) in a two-level dry primitive equation model with zonally symmetric boundary conditions and forced by Newtonian relaxation. The constant presence of a dominant low-frequency wave 5 in a variety of models and for different boundary conditions suggests that there must be a fundamental atmospheric process leading to its formation. HH proposed a quasigeostrophic (QG) inverse

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Kamel Chikhar and Pierre Gauthier

) ( Gauthier et al. 2007 ; Laroche et al. 2007 ) and those of ERA-Interim ( Dee et al. 2011 ), with the objective of studying the sensitivity to initial and boundary conditions. They showed that the analyses have a significant impact on the model and can lead to the emergence of a bias. On the other hand, a bias in the model can be caused by the lateral driving, and Chikhar and Gauthier (2015) used physical and dynamical tendencies to detect a sensitivity of the CRCM5 to changes in the lateral boundary

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