Turbulent eddy diffusivities for a planetary boundary layer generated by thermal and mechanical effects

Abstract

To estimate the superficial concentration of contaminants an eulerian model of dispersion was used, where the main scheme is the diffusion-advection equation that employs turbulent eddy diffusivity. The aim of this work is a comparison between different eddy diffusivity derivations for a planetary boundary layer turbulence generated by thermal and mechanical effects. The accuracy of eddy diffusivity derivations was evaluated by comparing the data simulated in the eulerian dispersion model and the observed concentrations of the Copenhagen and Praire Grass experiments. Three convective eddy diffusivity derivations were compared among themselves: 1) proposed by Degrazia et al., 2) proposed Hostlag & Moeng and 3) the derivation gotten by the parameters of Hanna. Two neutral eddy diffusivity derivations were also compared: 1) proposed by Degrazia et al. and 2) gotten by the parameters of Hanna. In order to improve the comparisons some adjustments and increments were made in Hostlag & Moeng derivation and in that gotten by the parameters of Hanna. We can observe that despite the eddy diffusivities having been formulated by different ways, the results were similar and sufficiently satisfactory. In the convective case, the best simulations of each derivation showed a Normalized Mean Squared Error between 0.04 and 0.05 when compared with Copenhagen dataset. © 2013 Sociedade Brasileira de Geofísica.