Keywords: density function, Lagrangian stochastic model, model evaluation, probability, urban convective boundary-layer
Intercomparison of Lagrangian stochastic models based on two different PDFs
In this work, two different Lagrangian stochastic models for convective turbulence are compared and tested against the Indianapolis dataset. The two models are based on the generalised Langevin equation, whose coefficients are solutions of the Fokker-Planck equation. The first model uses the bi-Gaussian probability density function (PDF) following Luhar and Britter (1989) and the second one, proposed by us (Ferrero and Anfossi, 1998), is based on the Gram-Charlier PDF. Both models are able to take into account up to the third order moment of the wind velocity fluctuation vertical component and make use of the Gaussian assumption in the horizontal directions. Basically, the two models considered here are different versions of our stochastic dispersion model for flat terrain, LAMBDA. This means that plume rise is taken into account and that the correct boundary conditions are used. The results obtained are presented and their differences discussed.