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Статті в журналах з теми "Couche limite atmosphérique (ABL)":
Boucher, Olivier, and Marie Doutriaux-Boucher. "Cellules de Bénard dans la soupe miso et dans la couche limite atmosphérique." La Météorologie 8, no. 91 (2015): 15. http://dx.doi.org/10.4267/2042/57857.
Дисертації з теми "Couche limite atmosphérique (ABL)":
Nishio, Yoshiyuki. "Challenges in applying the PSPG/SUPG Finite element method to the atmosphéric boundary layer." Thesis, La Rochelle, 2021. http://www.theses.fr/2021LAROS017.
In the context of a Chemical, Biological, Radiological, and Nuclear (CBRN) application for the Belgian Defense, the original objective of the work was to simulate a realistic open-air CBRN case (e.g. dispersion after an explosion of particles in a city), by applying the Streamline-Upwind Petrov-Galerkin (SUPG) stabilization on a nite element method (FEM), together with a second phase (i.e. particles). This would be done through the code Cool uid 3, a Domain Speci c Language (DSL) written in C++.However, open-air applications requires to describe the atmospheric bound-ary layer (ABL) correctly. This has never been done using stabilized FEM. Consequently, the challenge of this work is to answer the simple question: How to model an ABL taking advantage of the SUPG stabilization method.To reduce the number of elements produced by a wall-resolved simulation, the ABL was implemented with a wall model and veri ed in 2D, while a few corrections (e.g. grid scalability, stable velocity pro le) could also be adressed.However, the 3D implementation revealed spurious oscillations, suggesting a numerical origin. Although SUPG does provide dissipation, it seemed not su cient enough for such a high Reynolds ow. Consequently, two directions were followed to add numerical dissipation: Firstly, the implementation of an extended version of the SUPG, the Variational MultiScale method (VMS), was initiated. The latter provides a combined framework for stabilization and turbulence modeling. Secondly, two LES formulations, known for their dissipative behavior, were integrated.Having solved the spurious oscillations, the velocity pro le was analyzed. Eventually, the viscous Reynolds number for the ABL domain was reduced to enable the comparison with an available DNS result. Fortunately, rela-tive to the standard no-slip wall condition and to the friction velocity condi-tion, the wall model implementation provided the best result, although not matching.In conclusion, we ascertained two methodologies (LES and SUPG / VMS) that have the potential to approach the ABL ow. The stabilized FEM using SUPG revealed that it is currently not su cient to avoid spurious oscillations in the case of an ABL ow. In contrast, LES provided encouraging results for reduced Reynolds number, supporting that some kind of turbulence model is indispensable. This emphasizes that the implementation of VMS should be promising, although challenging
Réchou, Anne. "Structure turbulente de la couche limite atmosphérique marine (expérience SOFIA)." Toulouse 3, 1995. http://www.theses.fr/1995TOU30058.
Rodier, Quentin. "Paramétrisation de la turbulence atmosphérique dans la couche limite stable." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30343/document.
The modeling of the stable atmospheric boundary layer is one of the current challenge faced by weather and climate models. The stable boundary layer is a key for the prediction of fog, surface frost, temperature inversion, low-level jet and pollution peaks. Furthermore, polar regions, where stable boundary layer predominates, are one of the region with the largest temperature rise : the stable boundary layer modeling is crucial for the reduction of the spread of climate predictions. Since more than 15 years, the GABLS models intercomparison exercices have shown that turbulent mixing in the stable boundary layer is overestimated by numerical weather prediction models. Numerous models artificially strengthen the activity of their turbulence scheme to avoid a laminarization of the flow at a critical value of the gradient Richardson number. The existence of this threshold is only a theoretical and a numerical issues. Numerous observations and high-resolution numerical simulations do not support this concept and show two different regimes : the weakly stable boundary layer that is continuously and strongly turbulent; and the very stable boundary layer globally intermittent with a highly anisotropic and very weak turbulence. This thesis aims at improving the turbulence scheme within the atmospheric research model Méso-NH developped by Météo-France and the Laboratoire d'Aérologie, and the operational weather forecast model AROME. We use a traditional methodology based on the comparison of high-resolution simulations that dynamically resolve the most energetic turbulent eddies (Large-Eddy Simulations) to single-column simulations. Several LES covering the weakly and the very stable boundary layer were performed with Méso-NH. The limits of applicability of LES in stratified conditions are documented. The first part of the study deals with the overmixing in the weakly stable boundary layer. We propose a new diagnostic formulation for the mixing length which is a key parameter for turbulence schemes based on a prognostic equation for the turbulent kinetic energy. The new formulation adds a local vertical wind shear term to a non-local buoyancy-based mixing length currently used in Méso-NH and in the French operational model AROME. The new scheme is evaluated first in single-column simulations with Méso-NH and compared to LES, and then in the AROME model with respect to observations collected from the operational network of Météo-France. The second part presents a theoretical and numerical evaluation of a turbulence scheme based on two prognostic equations for the turbulent kinetic and potentiel energies. In stratified conditions, the heat flux contributes to the production of turbulent potential energy. The laminarization of the flow is then limited by a reduction of the destruction of the turbulent kinetic energy by a better representation of the anisotropy and a counter-gradient term in the heat flux. On the simulated cases, this new formulation behaves similarly than the scheme with one equation for the turbulent kinetic energy because the self-preservation mechanism is not dominant compared to the dissipation term. Further research should improve the turbulent kinetic energy dissipation closure in the very stable regime
Frangi, Jean-Pierre. "Dynamique de la couche limite de surface sahélienne." Toulouse 3, 1988. http://www.theses.fr/1988TOU30247.
Arduini, Gabriele. "Processus de la couche limite atmosphérique stable hivernale en vallée alpine." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU006/document.
Alpine valleys are rarely closed systems, implying that the atmospheric boundary layer of a particular valley is influenced by the surrounding terrain and large-scale flows. A detailed characterisation and quantification of these effects is required in order to design appropriate parameterisation schemes for complex terrains. The focus of this work is to improve the understanding of the effects of surrounding terrain (plains, valleys or tributaries) on the heat and mass budgets of the stable boundary layer of a valley, under dry and weak large-scale wind conditions. Numerical simulations using idealised and real frameworks are performed to meet this goal. Several idealised terrains (configurations) were considered: an infinitely long valley (i.e. two-dimensional), and upstream valleys opening either on a plain (valley-plain), on a wider valley (draining) or on a narrower valley (pooling). In three-dimensional valleys, two main regimes can be identified for all configurations: a transient regime, before the down-valley flow develops, followed by a quasi-steady regime, when the down-valley flow is fully developed. The presence of a downstream valley reduces the along-valley temperature difference, therefore leading to weaker down-valley flows. As a result, the duration of the transient regime increases compared to the respective valley-plain configuration. Its duration is longest for pooling configuration. For strong pooling the along-valley temperature difference can reverse, forcing up-valley flows from the narrower towards the wider valley. In this regime, the volume-averaged cooling rate is found maximum and its magnitude dependent on the configuration considered. Therefore pooling and draining induce colder and deeper boundary layers than the respective valley-plain configurations. In the quasi-steady regime the cooling rate is smaller than in the transient regime, and almost independent of the configuration considered. Indeed, as the pooling character is more pronounced, the warming contribution from advection to the heat budget decreases because of weaker down-valley flows, and so does the cooling contribution from the surface sensible heat flux. The mass budget of the valley boundary layer was found to be controlled by a balance between the convergence of downslope flows at the boundary layer top and the divergence of down-valley flows along the valley axis, with negligible contributions of subsidence far from the slopes. The mass budget highlighted the importance of the return current above the down-valley flow, which may contribute significantly to the inflow of air at the top of the boundary layer. A case-study of a persistent cold-air pool event which occurred in February 2015 in the Arve River Valley during the intensive observation period 1 of the PASSY-2015 field campaign, allowed to quantify the effects of neighbouring valleys on the heat and mass budgets of a real valley atmosphere. The cold-air pool persisted because of warm air advection at the valley top, associated with the passage of an upper-level ridge over Europe. The contributions from each tributary valley to the mass and heat budgets of the valley atmosphere were found to vary from day to day within the persistent stage of the cold-air pool, depending on the large-scale flow. Tributary flows had significant impact on the height of the inversion layer and the strength of the cold-air pool, transporting a significant amount of mass within the valley atmosphere throughout the night. The strong stratification of the near-surface atmosphere prevented the tributary flows from penetrating down to the valley floor. The evolution of the large-scale flow during the episode had a profound impact on the near-surface circulation of the valley. The channelling of the large-scale flow at night, can lead to the decrease of the horizontal temperature difference driving the near-surface down-valley flow, favouring the stagnation of the air close to the ground
Branchet, Bérengère. "Analyse d'un modèle de couche limite atmosphérique bidimensionnel non-hydrostatique anélastique." Bordeaux 1, 1998. http://www.theses.fr/1998BOR10531.
Tignat-Perrier, Romie. "Facteurs de structuration des communautés microbiennes de la couche limite atmosphérique." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAU034.
Up to 106 microbial cells per cubic meter are found in suspension in the planetary boundary layer, the lowest part of the atmosphere. Direct influences of the planetary boundary layer on humans, crops and diverse ecosystems like soils and oceans make the full understanding of its composition, both chemical and microbiological, of utmost importance. While microbial communities of the planetary boundary layer vary significantly at different temporal and spatial scales, they remain largely unexplored. The main goal of this thesis was to understand how airborne microbial communities are structured in the troposphere with special emphasis on the planetary boundary layer and to identify their main controlling factors. We investigated both the taxonomic and functional composition of airborne microbial communities in the dry phase (i.e. not cloud-associated) over time at nine different geographical sites around the world using high throughput sequencing technologies.Our investigation that focused on microbial taxonomy showed that local landscapes were the main contributors to the global distribution of airborne microbial communities despite the potential occurrence of long-range transport of airborne microorganisms. We also observed that meteorology and the diversity of the surrounding landscapes played major roles in the temporal variation of the microbial community structure in the planetary boundary layer. We further explored the temporal variation of airborne microbial communities at a continental and mountainous site in France (1465 m above sea level) over a full-year. This study demonstrated the importance of the surface conditions (i.e. vegetation, snow cover etc.) of the surrounding landscapes on the taxonomic composition of airborne microorganisms. The seasonal changes in agricultural and vegetated areas, which represented a significant part of the site’s surrounding landscape, were correlated to the shifts in the taxonomic composition of airborne microbial communities during the year. Finally, we investigated the functional composition of microbial communities of the planetary boundary layer to identify whether the physical and chemical conditions of the atmosphere played a role in selection or microbial adaptation of airborne microorganisms. The comparative metagenomic analysis did not show a specific atmospheric signature in the functional potential of airborne microbial communities. To the contrary, their functional composition was mainly correlated to the underlying ecosystems. However, we also showed that fungi were more dominant relatively to bacteria in air as compared to other (planetary bound) ecosystems. This result suggested a selective process for fungi during aerosolization and/or aerial transport and that fungi might likely survive aerosolization and/or aerial transport better than bacteria due to their innate resistance to stressful physical conditions (i.e. UV radiation, desiccation etc.). Our results provide a clearer understanding of the factors (i.e. surrounding landscapes, distant sources, local meteorology, and stressful physical atmospheric conditions) that control the distribution of microbial communities in the atmospheric boundary layer. Our investigations provide a basis for further studies on the prediction and even control of airborne microbial communities that would be of interest for public health and agriculture
Zegadi, Rabah. "Contribution à l'étude de la couche de surface atmosphérique, en situation stable, simulée en soufflerie." Ecully, Ecole centrale de Lyon, 1991. http://www.theses.fr/1991ECDLA012.
Mathieu, Anne. "Analyse synoptique de la couche limite atmosphérique marine pendant la campagne sémaphore." Paris 6, 2000. http://www.theses.fr/2000PA066315.
Delboulbé, Eric. "Simulation numérique des écoulements de couche limite atmosphérique autour de structures bâties." Aix-Marseille 2, 1997. http://www.theses.fr/1997AIX22070.