ABSTRACT
This chapter aims to present and discuss some general characteristics of a fully developed turbulence. It examines two phenomena associated to the turbulence and that frequently play a fundamental role in describing contaminants dispersion in a planetary boundary layer. One of these phenomena concerns the turbulence decaying in a convective boundary layer. This dynamical process, which occurs in the characteristic sunset transition time, is responsible for sustaining turbulence in the residual layer. The second phenomenon occurs in situations characterized by low wind speed (LWS). The study of LWS conditions is of interest, partly because the simulation of airborne pollutant dispersion in these conditions is rather difficult. The Eulerian velocity structure function must be distinguished from the Lagrangian velocity structure function that is described in terms of the variation in velocity of a fluid particle as it moves about in the turbulent flow.
