Stochastic Fields Method for Sub-Grid Scale Emission Heterogeneity in Mesoscale Atmospheric Dispersion Models

The Field Monte Carlo or Stochastic Fields method for turbulent reacting flows has been applied to the issue of sub-grid scale emission heterogeneity in a mesoscale model. This method is a solution technique for the probability density function (PDF) transport equation and can be seen as a straightforward extension of currently used mesoscale dispersion models. It has been implemented in an existing mesoscale model and the results compared with Large-Eddy Simulation data simulation devised to test specifically the effect of sub-grid scale heterogeneity on upper-air concentration fluctuations. The sub-grid scale emission heterogeneity is assimilated in the model as a PDF of the emissions. The results show an excellent agreement without the need of setting any model constant other than the ones already used in the mesoscale model. The stochastic Fields method solve for the PDF of concentration of dispersing scalars and therefore it posses the ability of handling chemistry of any complexity without any closure assumption. This study shows for the first time the feasibility to apply this method to mesoscale chemical transport models.

CASSIANI Massimo;  VINUESA Jean Francois;  GALMARINI Stefano;  DEMBY Bruce; 

2009-07-27

Copernicus Publications

JRC50708