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On the Impact of Long Wind-Waves on Near-Surface Turbulence and Momentum Fluxes ArchiMer
Ayet, Alex; Chapron, Bertrand; Redelsperger, Jean-luc; Lapeyre, Guillaume; Marié, Louis.
We propose a new phenomenological model to represent the impact of wind-waves on the dissipation of turbulence kinetic energy near the sea surface. In this model, the momentum flux at a given height results from the averaged contribution of eddies attached to the sea surface whose sizes are related to the surface geometry. This yields a coupling between long wind-waves and turbulence at heights of about 10 m. This new wind-and-waves coupling is thus not exclusively confined to the short wave range and heights below 5 m, where most of the momentum transfer to the waves is known to occur. The proposed framework clarifies the impact of wind-waves on Monin–Obukhov similarity theory, and the role of long wind-waves on the observed wind-wave variability of...
Tipo: Text Palavras-chave: Air-sea fluxes; Wall-bounded turbulence; Wave boundary layer; Wind stress; Wind-waves.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00601/71285/69691.pdf
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Flux de quantité de mouvement à l'interface air-mer : approche théorique du couplage entre turbulence et vagues de vent ArchiMer
Ayet, Alex.
Despite numerous works, the causal link between wind and waves is still a controversial subject. This is due, among others, to the multi-scale nature of a realistic ocean surface and to wave breaking, which changes its topology. In this thesis, such problems are studied from a theoretical perspective, using a phenomenological model linking the spectral and averaged properties of wall-bounded turbulence through the geometry attached eddies.The first part of the thesis revisits this phenomenological model by questioning its underlying assumptions and, in particular, reveals inconsistencies in the models used for the energy redistribution between turbulence components (the Rotta model). The phenomenological model is then used to study the coupling between...
Tipo: Text Palavras-chave: Flux de quantité de mouvement; Turbulence proche de paroi; Budgets spectraux; Vagues de vent; Génération de vagues; Interactions air-mer; Momentum flux; Wall-bounded turbulence; Spectral budgets; Wind-waves; Wave generation; Airsea interactions.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00692/80427/83563.pdf
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An analytical study of the atmospheric boundary layer flow and divergence over a SST front ArchiMer
Ayet, Alex; Redelsperger, Jean-luc.
We present an analytical model reproducing literature‐based numerical simulations of the Marine Atmospheric Boundary Layer (MABL) over a SST front, with wind blowing from the cold to the warm side. Turbulence is parameterised through a varying diffusion coefficient with two critical features: it is parabolic on the vertical and its mean value is decoupled from the MABL height (unlike an Ekman layer model). These two novel features are found essential to recover the internal structure of the MABL from numerical simulations. Different dynamical regimes are obtained and interpreted in terms of non‐dimensional numbers characterising the relative importance of terms driving the momentum equation. A closed‐form expression of the vertically integrated wind...
Tipo: Text Palavras-chave: Air-sea interaction; Analytical model; Boundary-layer flow; SST front.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00501/61230/64808.pdf
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Scalewise Return‐to‐Isotropy in Stratified Boundary Layer Flows ArchiMer
Ayet, Alex; Katul, G. G.; Bragg, A. D.; Redelsperger, Jean-luc.
Anisotropic turbulence is ubiquitous in atmospheric and oceanic boundary layers due to differences in energy injection mechanisms. Unlike mechanical production that injects energy in the streamwise velocity component, buoyancy affects only the vertical velocity component. This anisotropy in energy sources, quantified by the flux Richardson number Ri f , is compensated by a `return to isotropy' (RTI) tendency of turbulent flows. Describing RTI in Reynolds‐averaged models and across scales continues to be a challenge in stratified turbulent flows. Using phenomenological models for spectral energy transfers, the necessary conditions for which the widely used Rotta model captures RTI across various Ri f and eddy sizes is discussed for the first time. This work...
Tipo: Text Palavras-chave: Boundary layer turbulence<; /AUTHOR_KEYWORD>; Rotta model<; /AUTHOR_KEYWORD>; Turbulence closure models<; /AUTHOR_KEYWORD>; Stratified turbulence<; /AUTHOR_KEYWORD>; Return to isotropy<; /AUTHOR_KEYWORD>.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00641/75294/75753.pdf
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Nowcasting solar irradiance using an analog method and geostationary satellite images ArchiMer
Ayet, Alex; Tandeo, P..
Accurate forecasting of Global Horizontal Irradiance (GHI) is essential for the integration of the solar resource in an electrical grid. We present a novel data-driven method aimed at delivering up to 6 h hourly probabilistic forecasts of GHI on top of a localized solar energy source. The method does not require calibration to adapt to regional differences in cloud dynamics, and uses only one type of data, covering Europe and Africa. It is thus suited for applications that require a GHI forecast for solar energy sources at different locations with few ground measurements. Cloud dynamics are emulated using an analog method based on 5 years of hourly images of geostationary satellite-derived irradiance, without using any numerical prediction model. This...
Tipo: Text Palavras-chave: Satellite-derived irradiance; Short term forecasting; Analog method; Geostationary satellite; PV.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00431/54229/56000.pdf
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Integrated Observations of Global Surface Winds, Currents, and Waves: Requirements and Challenges for the Next Decade ArchiMer
Villas Bôas, Ana B.; Ardhuin, Fabrice; Ayet, Alex; Bourassa, Mark A.; Brandt, Peter; Chapron, Bertrand; Cornuelle, Bruce D.; Farrar, J. T.; Fewings, Melanie R.; Fox-kemper, Baylor; Gille, Sarah T.; Gommenginger, Christine; Heimbach, Patrick; Hell, Momme C.; Li, Qing; Mazloff, Matthew R.; Merrifield, Sophia T.; Mouche, Alexis; Rio,; Rodriguez, Ernesto; Shutler, Jamie D.; Subramanian, Aneesh C.; Terrill, Eric J.; Tsamados, Michel; Ubelmann, Clement; Van Sebille, Erik.
Ocean surface winds, currents, and waves play a crucial role in exchanges of momentum, energy, heat, freshwater, gases, and other tracers between the ocean, atmosphere, and ice. Despite surface waves being strongly coupled to the upper ocean circulation and the overlying atmosphere, efforts to improve ocean, atmospheric, and wave observations and models have evolved somewhat independently. From an observational point of view, community efforts to bridge this gap have led to proposals for satellite Doppler oceanography mission concepts, which could provide unprecedented measurements of absolute surface velocity and directional wave spectrum at global scales. This paper reviews the present state of observations of surface winds, currents, and waves, and it...
Tipo: Text Palavras-chave: Air-sea interactions; Doppler oceanography from space; Surface waves; Absolute surface velocity; Ocean surface winds.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00509/62083/66271.pdf
Registros recuperados: 6
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