Turbulence parameterisation for PBL dispersion models in all stability conditions

Accounting for the current knowledge of the planetary boundary layer (PBL) structure and characteristics, a new set of turbulence parameterisations to be used in atmospheric dispersion models has been derived. That is, expressions for the vertical profiles of the Lagrangian length scale li and time scale Ti and diffusion coefficient Ki, i=u, v, w, are proposed. The classical statistical diffusion theory, the observed spectral properties and observed characteristics of energy containing eddies are used to estimate these parameters. The results of this new method are shown to agree with previously determined parameterisations. In addition, these parameterisations give continuous values for the PBL at all elevations (z0 z h, zi) and all stability conditions from unstable to stable, where h and zi are the turbulent heights in stable or neutral and convective PBL, respectively, and L is the Monin–Obukhov length. It is the aim of this work to present the general derivations of these expressions and to show how they compare to previous results. Finally, a validation of the present parameterisation applied in a Lagrangian particle model, will be shown. The Copenhagen data set is simulated. This data set is particularly suited for this validation, since most of the Copenhagen tracer experiments were performed in stability conditions that are the result of the relative combination of wind shear and buoyancy forces. As a consequence, a parameterisation scheme, able to deal contemporary with neutral and slightly convective condition, is to be preferred.