4,172 research outputs found
Optimal boundary conditions at the staircase-shaped coastlines
A 4D-Var data assimilation technique is applied to the rectangular-box
configuration of the NEMO in order to identify the optimal parametrization of
boundary conditions at lateral boundaries. The case of the staircase-shaped
coastlines is studied by rotating the model grid around the center of the box.
It is shown that, in some cases, the formulation of the boundary conditions at
the exact boundary leads to appearance of exponentially growing modes while
optimal boundary conditions allow to correct the errors induced by the
staircase-like appriximation of the coastline.Comment: Submitted to Ocean Dynamics. (27/02/2014
Sensitivity of a Barotropic Ocean Model to Perturbations of the Bottom Topography
In this paper, we look for an operator that describes the relationship
between small errors in representation of the bottom topography in a barotropic
ocean model and the model's solution. The study shows that the model's solution
is very sensitive to topography perturbations in regions where the flow is
turbulent. On the other hand, the flow exhibits low sensitivity in laminar
regions. The quantitative measure of sensitivity is influenced essentially by
the error growing time. At short time scales, the sensitivity exhibits the
polynomial dependence on the error growing time. And in the long time limit,
the dependence becomes exponential
Boundary conditions control for a Shallow-Water model
A variational data assimilation technique was used to estimate optimal
discretization of interpolation operators and derivatives in the nodes adjacent
to the rigid boundary. Assimilation of artificially generated observational
data in the shallow-water model in a square box and assimilation of real
observations in the model of the Black sea are discussed. It is shown in both
experiments that controlling the discretization of operators near a rigid
boundary can bring the model solution closer to observations as in the
assimilation window and beyond the window. This type of control allows also to
improve climatic variability of the model.Comment: arXiv admin note: substantial text overlap with arXiv:1112.4293,
arXiv:1112.3503, arXiv:0905.470
Singular value decomposition for the 2D fan-beam Radon transform of tensor fields
In this article we study the fan-beam Radon transform of
symmetrical solenoidal 2D tensor fields of arbitrary rank in a unit disc
as the operator, acting from the object space to the data space
The orthogonal polynomial basis of solenoidal tensor
fields on the disc was built with the help of Zernike polynomials
and then a singular value decomposition (SVD) for the operator
was obtained. The inversion formula for the fan-beam tensor transform follows from this decomposition. Thus obtained inversion formula can be
used as a tomographic filter for splitting a known tensor field into potential
and solenoidal parts. Numerical results are presented.Comment: LaTeX, 37 pages with 5 figure
- …