Effective real refractive index of dry aerosols in the Antarctic boundary layer

The real refractive index (nr) of dry aerosols measured at an Antarctic site was calculated using two methods. Number size distributions were applied in a Mie model where nr was varied until the measured and modeled scattering coefficients matched. Ion concentrations analyzed from impactor samples were used for calculating size‐dependent nr. Generally the two methods were consistent with each other. The average iteration‐derived nr varied mainly between ∼1.4 and ∼1.5 but also unreasonably low values, nr < 1.3, were obtained in air masses from the ocean. Possible explanations, such as inaccuracies in the method, water in the particles, non‐analyzed biogenic particles, or non‐spherical particles being responsible for the low values are discussed.