EFFECT OF ATMOSPHERIC RELATIVE-HUMIDITY ON AEROSOL-SIZE DISTRIBUTION

A method of accounting for the effect of variation in relative humidity on aerosol size distribution obtained from a low-pressure impactor (LPI) experiment is proposed. The size distribution of atmospheric aerosols under the prevailing relative humidities estimated by this method is compared with that obtained using a bistatic CW lidar. These results are used to study the effect of relative humidity on aerosol size distributions. At higher altitudes in the mixing region, increase in relative humidity causes a decrease in aerosol size index. The seasonal variation of aerosol number density near the surface is found to agree fairly well with the seasonal variation of the mixing region aerosol optical depth.