Effect of relative humidity on the scattering properties of urban aerosol particles

Abstract

The effect of increase in relative humidity on the angular variation of scattered light intensity distribution function and on asymmetry factor has been studied theoretically for three sizes of particles which are representative of urban aerosols. The increase in relative humidity causes change in physical properties of the particles, like radius (r) and complex refractive index (n-ik). The study is based on these changes in physical characteristics. It has been found that there are almost negligible changes in the function i at low humidities (≤40%) for all the three aerosol sizes studied, which may be due to insignificant changes in the physical properties. At higher values, however, the physical parameters as well as the function i show significant changes. The changes in i are systematic for the particle very small compared to the wavelength of incident radiation but for the particles comparable or larger it is not so. The asymmetry factor changes with the increase in relative humidity, for smaller particle it increases and for two larger particles changes are of fluctuative nature. © 1984 Indian Academy of Sciences.