Development of an online radiative module for the computation of aerosol optical properties in 3-D atmospheric models: validation during the EUCAARI campaign

Obtaining a good description of aerosol optical properties for a physically and chemically complex evolving aerosol is computationally very expensive at present. The goal of this work is to propose a new numerical module computing the optical properties for complex aerosol particles at low numerical cost so that it can be implemented in atmospheric models. This method aims to compute the optical properties online as a function of a given complex refractive index deduced from the aerosol chemical composition and the size parameters corresponding to the particles. The construction of look-up tables from the imaginary and the real part of the complex refractive index and size parameters will also be explained. This approach is validated for observations acquired during the EUCAARI (European integrated project on aerosol cloud climate air quality interactions) campaign on the Cabauw tower during May 2008 and its computing cost is also estimated. These comparisons show that the module manages to reproduce the scattering and absorbing behaviour of the aerosol during most of the fifteen-day period of observation with a very cheap computationally cost.