Aggregation-induced enhancements in aerosol absorption and scattering across the black-brown continuum

•Investigated the impact of aggregation on black-brown carbon optical properties.•Enhancement in optical properties is function of size parameter and imaginary refractive index.•Aggregation enhances absorption and scattering cross-sections up to 20% and 600%, respectively.•Asymmetry parameter is a strong function of the number of aggregate monomers.•Absorption Ångström Exponent decreases with aggregation.