Nonlinear processes, such as passive scalar fluctuations driven by the turbulent wind field, exhibit extreme variability over a wide range of space-time scales and intensifies. As a resuit, of the complexity of those fields, the theoretical treatment of turbulence is a long-standing challenge of fluid mechanics. An empirical study of stochastic fluctuations in atmospheric aerosol concentration using state of the art lidar data is the subject of this thesis. The statistics of the fluctuations in the scalar field are closely related to those of the turbulent Avind field. Initially, a detailed review of the treatments of such turbulent atmospheric fields that is commonly found in the littérature is given. The main strands of research relevant to a statistical understanding of atmospheric dynamics are (1) isotropic hydrodynamic turbulence in 2D and 3D (with extensions), (2) buoyancy driven flows (3) gravity wave theories, (4) closures, (5) direct numerical simulations. It is argued that all current approaches treat the anisotropy of the dynamics and the characteristic intermittency inappropriately. Already existing - albeit limited - empirical evidence is then used to motivate the relevance of Generalized Scale Invariance and the Unified Scaling Model (e.g. [Schertzer and Lovejoy, 1983, 1984, 1985]) Avhich models turbulent atmospheric fields as anisotropic multifractal cascade processes. This model implies the anisotropic multiscaling of the fields over the entire range of spatial scales and that variability increases algebraically downscale leading to a highly intermittent field.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.19727 |
| Date | January 2003 |
| Creators | Lilley, Marc |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physics) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002022810, Theses scanned by McGill Library. |
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