EFFECTS OF VARIATION IN WATER SOLUBLE AEROSOL CONCENTRATIONS AND RELATIVE HUMIDITY IMPACT ON THE POLARIZABILITY AND PHASE FUNCTION OF URBAN ATMOSPHERE

Abstract: This research investigates how changes in water-soluble aerosol concentrations and relative humidity (RH) affect the optical properties of irregularly-shaped urban aerosols. Using the Optical Properties of Aerosols and Clouds software (OPAC 4.0), urban aerosol optical properties at visible wavelengths (0.4-0.8 μm) were simulated across eight relative humidities (0%,50%,70%,80%,90%,95%,98%,99%). We applied Stokes parameters to calculate phase functions and combined Claussi-Massoti formulation with Maxwell and Lorentz-Lorentz relations were used for computation of effective polarizabilities. The results reveal new information on how RH and aerosol concentration impact urban aerosol optical properties. Notably, we determined effective polarizabilities, polarization, and phase function data using OPAC 4.0 and determined aerosol size growth curves’ mean exponent through effective hygroscopic growth. Effective polarizability exhibits a decrease with increasing wavelength and water-soluble aerosols concentration, whereas it increases with rising relative humidity. Phase function decreases with the increase in wavelength and also, decreases with the increase in scattering angle, satisfies power law. When all the plots were compared, phase functions increase with the increase in relative humidity, increases with the increase in the concentration of water-soluble aerosols.