Modification of the SAFE_AIR II dispersion code for urban applications

The paper focuses on simple Urban Boundary Layer (UBL) parameterisations and their implementation in the SAFE_AIR II code, developed at the University of Genoa. As a first step towards the model's use in an urban environment we implement the concept of local scaling in the roughness sublayer (RSL) while estimating the sigma functions in the dispersive part of the model. Preliminary results for the experiments of the Copenhagen data set are presented using both urban and non-urban options. The effect of RSL height - a main parameter in the local scaling approach, is discussed on the basis of comparison between measured and simulated maximum concentration values for the nearest arc to the source using two different sigma functions available in the present version of the code.