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Dynamic Characteristics of Regional Flows around the Pyrénées in View of the PYREX Experiment. Part II: Solution of a Linear Model Compared to Field Measurements

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  • a Laboratoire d’Aerologie, Universite Paul Sabatier, Toulouse, France
  • | b Centre National de Recherches Meteorologiques, Meteo-France, Toulouse, France
  • | c Department of Environmental Researches, Nuclear Research Centre, Negev, Israel
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Abstract

This paper considers a linear hydrostatic model of a stable, uniform, constant rotational airflow over three- dimensional, elliptic, cross-sectional families of mountains in a z system. The surface pressure and the winds that are induced around the mountain chain are deduced using Fourier representation in both horizontal directions. The surface pressure perturbations and the induced wind intensities are linked to 1) the incoming airmass thermodynamic properties through Froude and Rossby numbers, 2) the geometrical aspect ratio of the mountain, 3) the direction of incidence of the incoming flow relative to the mountain orientation, and 4) the Coriolis effect through the Rossby number. The balance between the different factors that contribute to the morphology of the pressure and wind fields was established for northerly and southerly incoming flows that were blocked by an elliptical barrier resembling the Pyrénées mountain chain. Fair agreement was found between the results of the model and the experimental data collected during PYREX (Pyrénées experiment) intensive operational periods, with special regard to the asymmetry of the lateral flow for northerly incoming air masses.

Corresponding author address: Dr. B. Benech, Centre de Recherches Atmospheriques, 65300 Lannemezan, France.

benb@aero.obs-mip.fr

Abstract

This paper considers a linear hydrostatic model of a stable, uniform, constant rotational airflow over three- dimensional, elliptic, cross-sectional families of mountains in a z system. The surface pressure and the winds that are induced around the mountain chain are deduced using Fourier representation in both horizontal directions. The surface pressure perturbations and the induced wind intensities are linked to 1) the incoming airmass thermodynamic properties through Froude and Rossby numbers, 2) the geometrical aspect ratio of the mountain, 3) the direction of incidence of the incoming flow relative to the mountain orientation, and 4) the Coriolis effect through the Rossby number. The balance between the different factors that contribute to the morphology of the pressure and wind fields was established for northerly and southerly incoming flows that were blocked by an elliptical barrier resembling the Pyrénées mountain chain. Fair agreement was found between the results of the model and the experimental data collected during PYREX (Pyrénées experiment) intensive operational periods, with special regard to the asymmetry of the lateral flow for northerly incoming air masses.

Corresponding author address: Dr. B. Benech, Centre de Recherches Atmospheriques, 65300 Lannemezan, France.

benb@aero.obs-mip.fr

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