Choice of an advection scheme for biogeochemical models

Lévy, Marina; Estublier, Audrey; Madec, Gurvan

doi:10.1029/2001gl012947

Cited by 129 publications

(105 citation statements)

References 11 publications

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“…Numerical analysis of the advection of atmospheric tracers is known to be challenging (Hourdin and Armengaud, 1999;Lévy et al, 2001). The accuracy of the numerical scheme may have a significant impact on the performance of the simulation.…”

Section: Transport Numerical Schemesmentioning

confidence: 99%

Parameter‐field estimation for atmospheric dispersion: application to the Chernobyl accident using 4D‐Var

Bocquet

2011

Quart J Royal Meteoro Soc

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Atmospheric chemistry and air-quality numerical models are driven by uncertain forcing fields: emissions, boundary conditions, wind fields, vertical turbulent diffusivity, kinetic chemical rates, etc. Data assimilation can help to assess these parameters or fields of parameters. Because such parameters are often much more uncertain than the fields diagnosed in meteorology and oceanography, data assimilation is much more of an inverse modelling challenge in this context. In this article these ideas are experimented with by revisiting the Chernobyl accident dispersion event over Europe. A fast four-dimensional variational scheme (4D-Var) is developed, which seems appropriate for the retrieval of large parameter fields from large observation sets and the retrieval of parameters that are nonlinearly related to concentrations. The 4D-Var, and especially an approximate adjoint of the transport model, is tested and validated using several advection schemes that are influential on the forward simulation as well as on the data-assimilation results. Firstly, the inverse modelling system is applied to the assessment of the dry and wet deposition parameters. It is then applied to the retrieval of the emission field alone, the joint optimization of removal-process parameters and source parameters and the optimization of larger parameter fields such as horizontal and vertical diffusivities or the dry-deposition velocity field. The physical parameters used so far in the literature for the Chernobyl dispersion simulation are partly supported by this study. The crucial question of deciding whether such an inversion is merely a tuning of parameters or a retrieval of physically meaningful quantities is discussed. Even though inversion of parameter fields may fail to determine physical values for the parameters, it achieves statistical adaptation that partially corrects for model errors and, using the inverted parameter fields, leads to considerable improvement in the simulation scores.

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Section: Transport Numerical Schemesmentioning

confidence: 99%

Parameter‐field estimation for atmospheric dispersion: application to the Chernobyl accident using 4D‐Var

Bocquet

2011

Quart J Royal Meteoro Soc

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“…1, and the model equations are given in Hemmings et al (2008). The state variables are all treated as oceanic tracers, and are advected using the Monotonic Upstream Scheme for Conservation Laws (MUSCL) scheme, which forms part of the NEMO code (Lévy et al, 2001). Chlorophyll, which is assimilated in this study, is not a state variable within the model, but is derived from phytoplankton using nitrogen to carbon and carbon to chlorophyll ratios.…”

Section: Model Descriptionmentioning

confidence: 99%

Assimilating GlobColour ocean colour data into a pre-operational physical-biogeochemical model

et al. 2012

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Abstract. As part of the GlobColour project, daily chlorophyll a observations, derived using remotely sensed ocean colour data from the MERIS, MODIS and SeaWiFS sensors, are produced. The ability of these products to be assimilated into a pre-operational global coupled physicalbiogeochemical model has been tested, on both a hindcast and near-real-time basis, and the impact on the system assessed. The assimilation was found to immediately and considerably improve the bias, root mean square error and correlation of modelled surface chlorophyll concentration compared to the GlobColour observations, an improvement which was sustained throughout the year and in every ocean basin. Errors against independent in situ chlorophyll observations were also reduced, both at and beneath the ocean surface. However, the model fit to in situ observations was not consistently better than that of climatology, due to errors in the underlying model. The assimilation scheme used is multivariate, updating all biogeochemical model state variables at all depths. The other variables were not degraded by the assimilation, with annual mean surface fields of nutrients, alkalinity and carbon variables remaining of similar quality compared to climatology. There was evidence of improved representation of zooplankton concentration, and reduced errors were seen against in situ observations of nitrate and pCO 2 , but too few observations were available to conclude about global model skill. The near-real-time GlobColour products were found to be sufficiently reliable for operational purposes, and of benefit to both operational-style systems and reanalyses.

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“…The simulations presented here use a Flux Corrected Transport (FCT) scheme (Lévy et al, 2001) for tracer advection. Climatological initial conditions for temperature and salinity are taken in January from PHC2.1 (Steele et al, 2001) at high latitudes, MEDATLAS (Jourdan et al, 1998) in the Mediterranean, and Levitus et al (1998) elsewhere.…”

Section: Model Configurations Experimentsmentioning

confidence: 99%

Influence of numerical schemes on current-topography interactions in 1/4° global ocean simulations

et al. 2007

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Abstract. The combined use of partial steps and of an energy-enstrophy conserving momentum advection scheme was shown by Barnier et al. (2006) to yield substantial improvements in the surface solution of the DRAKKAR 1 4• global sea-ice/ocean model. The present study extends this investigation below the surface with a special focus on the Atlantic and reveals many improvements there as well: e.g. more realistic path, structure and transports of major currents (Gulf Stream, North Atlantic Current, Confluence region, Zapiola anticyclone), behavior of shedded rings, narrower subsurface boundary currents, stronger mean and eddy flows (MKE and EKE) at depth, beneficial enhancement of cyclonic (anticyclonic) flows around topographic depressions (mountains). Interestingly, adding a no-slip boundary condition to this improved model setup cancels most of these improvements, bringing back the biases diagnosed without the improved momentum advection scheme and partial steps (these biases are typical of other models at comparable or higher resolutions). This shows that current-topography interactions and full-depth eddy-admitting model solutions can be seriously deteriorated by near-bottom sidewall friction, either explicit or inherent to inadequate numerical schemes.

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Choice of an advection scheme for biogeochemical models

Cited by 129 publications

References 11 publications

Parameter‐field estimation for atmospheric dispersion: application to the Chernobyl accident using 4D‐Var

Parameter‐field estimation for atmospheric dispersion: application to the Chernobyl accident using 4D‐Var

Assimilating GlobColour ocean colour data into a pre-operational physical-biogeochemical model

Influence of numerical schemes on current-topography interactions in 1/4° global ocean simulations

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