Effect of Relative Humidity on Arctic Aerosols

Abstract

In this paper, the authors investigated some microphysical and optical properties of arctic aerosols extracted from the data base Optical Properties of Aerosols and Clouds(OPAC) to determine the effect of hygroscopic growth at the spectral range of 0.25?m to 2.5?m and eight relative humilities (RHs) (0, 50, 70, 80, 90, 95, 98, and 99%).The microphysical properties extracted were radii, volume mix ratio, number mix ratio and mass mix ratio as a function of RH while the optical properties are scattering and absorption coefficients and asymmetric parameters. Using the microphysical properties, effective growth factors of the mixtures were determined while using optical properties enhancement parameters were determined and then parameterized using some models. We observed that the data fitted the models very well. The angstrom coefficients which determined the type of particles size distribution increases with the increase in RHs except at the delinquent point where it decreases with the increase in RHs. The mixture was determined to have bimodal type of distribution with the dominance of fine mode particles but non-spherical.

Keywords: microphysical properties, optical properties, hygroscopic growth, enhancement parameters, models, parametrisation.