Parametrisation of effective hygroscopic growths, kelvin effects and water activities of atmospheric aerosols

Abstract

In this paper the effective hygroscopic growths of atmospheric aerosols and effective radii using microphysical properties of atmospheric aerosols are extracted from Optical Properties of Aerosols and Cloud (OPAC) at seven relative humidity (50%,70%,80%,90%,95%,98% and 99%). The microphysical properties extracted were radii of the individual aerosols and the volume mix ratios as functions of relative humidity (RH). The effective hygroscopic growths and effective raii were parameterized and the modified Kholer equation was used to determine the hygroscopicity, water activities, kelvin effects, and humidification factors. It was observed that the data fitted the models very well. The highest valuefor Kelvin effect
at 50% RH (k_eff = 1.351) was found in maritime tropical and lowest value at 50% RH (k_eff=0.977) found in maritime clean also for Kelvin effect at 99% RH the highest value was found in maritime tropical (k_eff=1.201) and the lowest at 99% RH (k_eff=0.988) was found in maritime clean and for water activities at 50% RH the highest value was found in continental clean (α_w = 1.534) and the lowest value of water activity at 50% RH was found in maritime tropical (α_w = 0.354) and also the highest value of water activity at 99% RH (α_w = 2.098) was found in continental clean and the lowest water activity value at 99% was found in maritime tropical (α_w = 0.7049).