This work presents the characterization of atmospheric aerosols performed over the Iberian Peninsula in the framework of EARLINET for a special episode on 20th August 2007. The assessment of aerosol radiative impact requires an accurate determination of their optical and microphysical properties, which are presented here for a variety of instrumentation including passive remote sensors, as sun-photometers, and active systems both ground-based and on board CALIPSO satellite. Measurements highlight the presence of a multilayered structure with a well-defined planetary boundary layer and biomass-particles in elevated layers, extending up to 7 km asl over the central Iberian Peninsula, and even higher, up to 9 km asl, at the southeastern part of the peninsula. Lidar computations reveal a contribution to the aerosol optical depth around 10-40% for these biomass-burning particles, with backscatter-related Angströ