Turbulent viscosity optimized by data assimilation
As an alternative approach to classical turbulence modelling using a first or second order closure, the data assimilation method of optimal control is applied to estimate a time and space-dependent turbulent viscosity in a three-dimensional oceanic circulation model. The optimal control method,...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1999-11-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/17/1463/1999/angeo-17-1463-1999.pdf |
| Summary: | As an alternative approach to classical
turbulence modelling using a first or second order closure, the data
assimilation method of optimal control is applied to estimate a time and
space-dependent turbulent viscosity in a three-dimensional oceanic circulation
model. The optimal control method, described for a 3-D primitive equation model,
involves the minimization of a cost function that quantifies the discrepancies
between the simulations and the observations. An iterative algorithm is obtained
via the adjoint model resolution. In a first experiment, a <i>k</i> + <i>L</i>
model is used to simulate the one-dimensional development of inertial
oscillations resulting from a wind stress at the sea surface and with the
presence of a halocline. These results are used as synthetic observations to be
assimilated. The turbulent viscosity is then recovered without the <i>k</i> + <i>L</i>
closure, even with sparse and noisy observations. The problems of
controllability and of the dimensions of the control are then discussed. A
second experiment consists of a two-dimensional schematic simulation. A 2-D
turbulent viscosity field is estimated from data on the initial and final states
of a coastal upwelling event.<br><br><b>Key words.</b> Oceanography: general (numerical modelling)
· Oceanography: physical (turbulence · diffusion · and mixing processes) |
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| ISSN: | 0992-7689 1432-0576 |