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Habilitation à diriger des recherches

DYNAMIQUE DE LA COUCHE LIMITE ATMOSPHERIQUE:
DE LA TURBULENCE AUX SYSTEMES DE MESO-ECHELLE

Abstract : The planetary boundary layer (PBL), at the interface between the surface and the free troposphere, is the region of transfer of energy (momentum, sensible and latent heat), wator vapor and pollutants between the surface and the free troposphere, upon which depends the horizontal and vertical distribution of clouds, aerosols and chemical species. The global understanding of physical processes in the PBL and their impact on the largest scales is an open field of high priority research activity. Indeed, their account in numerical models (from large-eddy simulations (LES) to limited area models (LAM) and global circulation models (GCM)) is a major issue for the understanding of climate and its evolution in relation with human activity.

If the main atmospheric physical processes have been identified and analyzed for several decades, the improvement of numerical weather prediction (NWP) models require a re-examination of these processes to quantify more accurately their effects, to develop more accurate and reliable parameterizations and to evaluate the transport of chemical species in the atmosphere. I have thus focused my research effort on the PBL processes and their impact on regional scale, from turbulence to meso-scale systems. In detail, I have studied for the past years:
1. turbulence driven vertical exchanges between the surface and the PBL and particularly the structure and parameterization of near-surface turbulence;
2. the impact of orography and surface heterogeneity (sea/land or rural/urban contrasts, land use,..) on PBL flow.
Moreover, I have significantly contributed to the development of lidars dedicated to the experimental investigation of the PBL at the studied scale range.

My choices have been motivated by the lack of knowledge of numerous processes driving PBL flow dynamics at these scales, partly due to the inappropriate experimental and numerical tools at that time. The recent development of numerical models covering turbulence-scale to meso-scale and of remote sensors with high spatial and temporal resolution allowed me to re-visit dynamical processes which were assumed understood. Turbulence is the most striking example, since it has been studied for many decades with the universal theory of homogeneous and isotropic turbulence by Kolmogorov in 1941. This theory is the fundamental basis of our understanding of atmospheric turbulence and of the parameterization in NWP models. The new numerical and experimental tools allowed me to demonstrate the anisotropic nature of near-surface turbulence and its impact on energy transport and subgrid-scale parameterization.

Considering meso-scale systems, the impact of orography and surface heterogeneity have also been the subject of many studies, but most of them considered scales that could be documented by the existing sensors and/or numerical models at that time, that is scales larger than about 30 km typically in the late 80's early 90's. The striking example is for orographic flows. The PYREX experiment in 1990 allowed substantial progress in our understanding and modelling capability of mountain waves. However, this experiment allowed validate, or find the limits of theories that were suggested decades before (e.g. Queney, 1948). I thus focused my research effort on the understanding of PBL flow dynamics perturbed at various scales by the surface, using suited instruments and meso-scale models (Méso-NH and MM5) in the framework of MAP (Mesoscale Alpine Programme, fall 1999), which allowed a big step in our understanding of orographic flows and ESCOMPTE (Expérience sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d'Emissions, summer 2001) which aimed at studying thermal flows and their impact on pollutant transport.
Document type :
Habilitation à diriger des recherches
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https://tel.archives-ouvertes.fr/tel-00011118
Contributor : Philippe Drobinski <>
Submitted on : Friday, November 25, 2005 - 5:25:48 PM
Last modification on : Tuesday, December 8, 2020 - 3:43:50 AM
Long-term archiving on: : Friday, September 14, 2012 - 3:56:16 PM

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  • HAL Id : tel-00011118, version 1

Citation

Philippe Drobinski. DYNAMIQUE DE LA COUCHE LIMITE ATMOSPHERIQUE:
DE LA TURBULENCE AUX SYSTEMES DE MESO-ECHELLE. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI, 2005. ⟨tel-00011118⟩

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