Dynamique de la Couche Limite Atmosphérique stable en relief complexe. Application aux épisodes de pollution particulaire des vallées alpines.

Abstract : The study is focusing on the dynamics of the stably-stratified Atmospheric Boundary Layer in wintertime in valleys, especially during situations leading to PM10 pollution peaks. The analysis is made by means of LES-like numerical simulations and local measurements. In a first part, we study the katabatic wind created over the slopes of a narrow valley. We show that they are intermittent and turbulent and that their turbulent diffusivity is proportionnal to the square of a Froude number, and decreases with the ambient stratification. We also study the internal wave field generated by these winds and find that this frequency depends only on the stratification and seems to be independent of the characteristics of its source. In a second part, we study the valley wind system and the thermal inversions which occur by winter conditions in the valleys of the Grenoble area. Meteorological conditions leading to pollution episodes in the Grenoble valleys are also studied and their link with the previous mechanisms are explained. We show that these episodes take place during anticyclonic conditions, are induced by thermal inversion and that their evolution is linked to that of the weather regimes. During these episodes, we show that the local winds system is always the same, independent of the synoptical regime and consists of thermally-driven winds, whose spatial organization is controled by the geometry of the site. These currents are confined into a thermal inversion, which persists during the whole episode, and is however not destroyed during the day if the solar energy is not sufficient. The corresponding energy treshold is highlighted.
Document type :
Theses
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00606115
Contributor : Yann Largeron <>
Submitted on : Tuesday, July 5, 2011 - 2:11:57 PM
Last modification on : Thursday, January 3, 2019 - 4:30:08 PM
Long-term archiving on : Thursday, October 6, 2011 - 2:23:31 AM

Identifiers

  • HAL Id : tel-00606115, version 1

Collections

LEGI | UGA | UJF

Citation

Yann Largeron. Dynamique de la Couche Limite Atmosphérique stable en relief complexe. Application aux épisodes de pollution particulaire des vallées alpines.. Océan, Atmosphère. Université de Grenoble, 2010. Français. ⟨tel-00606115⟩

Share

Metrics

Record views

725

Files downloads

363