Les résultats de Pyrex

Bougeault, Philippe; Benech, B.; Bessemoulin, P.; Carissimo, B.; Jansa, A.; Pelon, J.; Petitdidier, M.; Richard, E.

doi:10.4267/2042/47000

Cited by 5 publications

(4 citation statements)

References 18 publications

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“…These simulations are generally considered to be quite reliable. As demonstrated for instance during the Pyrenees Experiment (Bougeault et al 1996), numerical models are able to predict the drying and warming effects associated with the subsidence downstream of major mountain ranges, as well as many aspects of the surface wind field and mountain waves. In contrast to these meso-beta scale aspects, little is known about the processes occurring at the meso-gamma scale inside the valleys themselves.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valley

Jaubert

Bougeault

Berger

et al. 2005

Q. J. R. Meteorol. Soc.

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SUMMARYThis paper examines the impact of a mesoscale analysis (2.5 km grid distance) on the simulation of the mesogamma scale aspects of föhn in the Rhine Valley. The föhn event, documented during IOP15 (5 November 1999) of the Mesoscale Alpine Programme, was standard in terms of intensity and was characterized by an important temporal variability. Many instruments operating in the Rhine valley target area are used to validate the simulation, in particular the airborne nadir-pointing lidar LEANDRE 2 (flown over the lower Rhine valley) as well as a wind profiler and a radio accoustic sounding system collocated in Rankweil, Austria. The large observational dataset acquired during the IOP allowed documentation of the entire föhn life cycle. For most of the IOP, a cold pool remained near the ground in the lower northern part of the valley. The non-hydrostatic model Meso-NH, used in a grid-nesting configuration with two nested models and initialized with a mesoscale analysis, allowed us to simulate realistically the location and depth of the cold pool. The relationship between the föhn intensity and the large-scale environment is also examined. The flow regime is a 'flow around' the Alps. The variability of this flow at the western tip of the Alps could explain some of the temporal changes observed at low level in the Rhine valley.

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valley

Jaubert

Bougeault

Berger

et al. 2005

Q. J. R. Meteorol. Soc.

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“…However, the lack of data in mountainous regions limits the understanding and the validation of the numerical simulations of the föhn. The necessity of a eld experiment was recognized early on and the Alpine Experiment (ALPEX) (Kuettner 1982) began to document this phenomenon over the Alps (Seibert 1990) as the Pyrenees Experiment (PYREX) (Bougeault et al 1990) had done over the Pyrenees. The föhn study in an Alpine valley has been recognized as a major scienti c objective of the Mesoscale Alpine Programme (MAP) (Binder et al 1996;Bougeault et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Multiscale and unsteady aspects of a deep föhn event during MAP

Jaubert

Stein

2003

Quart J Royal Meteoro Soc

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SUMMARYA strong föhn event occurring during the Mesoscale Alpine Programme Intensive Observing Period 2b (19)(20) is simulated with the non-hydrostatic model Meso-NH. The grid-nesting techniques and a suitable turbulence scheme allow a coherent downscaling from the analysed scales to the movements inside the Rhine Valley. The ow regime around the Alps changes from a ow-around regime to a ow-partly-over regime, when the wind increases ahead of the cold front. Simpli ed simulations allow us to estimate a non-dimensional height for the Alps which controls the ow regime. The föhn characteristics and its temporal evolution are discussed using both measurements and simulation. Backward trajectories show that the föhn air comes from an altitude around 2 km above the Po Valley. Nonlinear phenomena, such as wave breaking near 5 km above sea level just behind some secondary crests, and hydraulic jumps in the foothills, are found in the highest-resolution simulation, using a mesh of 625 m. This mesh clearly improves the comparison of the numerical simulation with the observations collected in the Rhine Valley. Mass budgets detail the progressive building of the föhn jet in the Rhine Valley.

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“…Le programme MAP a été proposé initialement en 1994 par MétéoSuisse et l'École polytechnique de Zurich (Binder et Schär, 1996). Il fait suite au programme Alpex, qui a été mené en 1982 sous l'égide de l'Organisation météorologique mondiale et a conduit à de nombreux progrès en météorologie alpine, et au programme Pyrex, mené sur les Pyrénées en 1990 par Météo-France, le CNRS et l'Institut météorologique espagnol (Bougeault et al, 1996). Une forte communauté s'est mobilisée suite à la proposition suisse : tous les pays alpins ont été impliqués, à la fois au niveau des services météorologiques et des agences de science fondamentale.…”

Section: Quand La Pluie Devient Malédictionunclassified

L'expérience MAP sur les phénomènes de mésoéchelle dans les Alpes - Premier bilan

Bougeault¹,

Richard²,

Roux³

2001

Météorologie

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La campagne de terrain du programme MAP (Mesoscale AlpineProgramme) s'est déroulée du 7 septembre au 15 novembre 1999, avec une très forte participation française. Elle avait pour but d'améliorer nos connaissances de base sur la physique des principaux risques météorolo-giques en montagne : les fortes pluies, les forts vents de vallée et la turbulence d'altitude. Il s'agissait aussi d'éprouver les capacités de la dernière génération de modèles numériques à maille très fine. Grâce à la bonne coopé-ration des très nombreux chercheurs participants et grâce à des conditions météorologiques exceptionnellement favorables, la campagne a été un plein succès et la plupart des objectifs expérimentaux ont pu être atteints. Le but de cet article est de présenter un premier bilan « à chaud » de l'expérience. The Mesoscale Alpine Programme (MAP) field experiment: first assessmentThe MAP field experiment ran from 7 September to 15 November 1999 with a very strong French presence. The objectives were to improve knowledge of the basic physics of some processes that generate meteorological hazards in mountain, such as heavy rainfall, strong valley winds, and turbulent airflow. Another objective was to test the new generation of high resolution numerical models. The field campaign benefited from excellent cooperation between the numerous scientists involved from many nations, and also from exceptionally favourable weather conditions. Almost all the experimental objectives were attained. This paper gives the hot news of the preliminary findings.

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Les résultats de Pyrex

Cited by 5 publications

References 18 publications

Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valley

Numerical simulation of meso-gamma scale features of föhn at ground level in the Rhine valley

Multiscale and unsteady aspects of a deep föhn event during MAP

L'expérience MAP sur les phénomènes de mésoéchelle dans les Alpes - Premier bilan

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