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The influence of turbulence on the meandering phenomenon is investigated. The study, based on the three-dimensional Navier-Stokes equations, shows that when the turbulent fluxes can be neglected an asymptotic solution results. This solution reproduces a horizontal wind oscillation with an infinite relaxation time. When there is turbulent forcing, on the other hand, a transition occurs to a new order, characterized by a spatial reorganization, leading to a wind field with a well-defined direction. [ABSTRACT FROM AUTHOR]

The dispersion of trace gases in the atmosphere depends on the state of the atmospheric boundary layer (ABL) and one of the most important parameters characterizing it is the intensity of turbulence within the ABL. Hence, the reliability of the atmospheric dispersion models depends on the way turbulent parameters are calculated and related to the structure of the ABL. Similarity theories are the usual tool used to study the ABL structure, and it is able to describe not only the distributions of turbulent statistical variables, but also profiles of the mean variables and spectra. Different kinds of similarity have different similarity scales, similarity relations and application ranges. There is a long history of field experiments contributing to the continuing development of similarity theories (Businger et al., 1971; Niewstadt, 1984; Sorbjan 1986; Mahrt et al. 1998) and the results of such studies lead to a well known description of the structure of turbulence over flat, homogeneous surfaces and various atmospheric conditions. However only in recent years attention has been devoted to the structure of the atmospheric turbulence over complex terrain. Kaimal and Finnigan (1994) addressed the problem of heterogeneity surface on several scales. On the smallest scale the effects are confined to the surface layer and it is related to local advection in micrometeorology, i.e. how far downwind of a change we must go to find a flow in equilibrium with the local surface. Over very complex terrain, however, this equilibrium may never be attained. [ABSTRACT FROM AUTHOR]

The literature regarding the Convective Boundary Layer (CBL) at early morning transition is scarce. Most papers are focused on the growth after convection is fully established. Tennekes (1973) proposes a conceptual model for the time required to erode the nocturnal inversion, while Kaimal et al. (1976) show a ‘typical' diurnal cycle of surface heat flux and Convective Boundary Layer depth, but this begins after the surface heat flux is already positive. Wyngaard (1983) discusses the morning (‘neutral-convective') transition briefly, and makes the point that only a relatively small buoyancy flux is needed to cause the transition. In this work, starting from the spectral form of the turbulent energy equation, a model for the CBL growing is described. [ABSTRACT FROM AUTHOR]