Introduction -- The basic definition of the planetary boundary layer -- A few words about turbulence -- The structure and evolution of the PBL -- The transport problem and the turbulent dispersion -- Observations -- Numerical experiments and simulations -- Appendix -- References -- A summary of mathematics and physics for PBL -- Eulerian and Lagrangian description -- The equations for velocity and passive scalars -- Stochastic variables -- Reynolds averaged equations -- Universal features of shear-dominated turbulence -- Exercises -- References -- The basic paradigm: horizontal homogeneity over flat terrain -- The governing equations -- Inner and outer scaling from the wind profile -- Similarity, Obukhov length and beyond -- The surface layer in neutral and unstable conditions -- The outer region in neutral conditions -- Some features of the convective boundary layer -- Stable boundary layers -- Some remarks about the spectra -- Exercises -- References -- Horizontal heterogeneities -- Explicit treatment vs. parameterization -- Internal boundary layers -- The boundary layer over hills and valleys -- Subgrid effects of the heterogeneous surface features -- Low wind, small vertical fluxes -- Canopy flow and the urban PBL -- Exercises -- References -- Turbulent dispersion -- The transport problem for fluid parcels -- Absolute dispersion of tracer parcels -- Two-parcel dispersion -- Meandering -- Observations of dispersion -- The stochastic approach to the absolute dispersion of tracer parcels -- Dispersion of inertial particles -- Exercises -- References -- Numerical modeling of turbulence for PBL flows -- Introduction -- Closures for the Reynolds-averaged equations -- Large Eddy Simulations -- Numerical simulations of PBL problems -- Exercises -- References -- Solutions -- References -- Index.