The Effect of Soot And Water Solubles in Radiative Forcing of Urban Aerosols

In this paper the optical depths, asymmetry parameters and single scattering albedos of urban aerosols were modeled using OPAC by altering the number densities of soot and water soluble at the spectral range of 0.25 μm to 1.0μm  at relative humidities (RHs) 0, 50, 70, 80, 90, 95, 98 and 99%. The data was used to calculate the radiative forcings(RF) and Angstom parameters. For the RF it was observed that as the RH increases there is a small increase in warming from 0 to 70% but as from 80 to 99% RH there is an increase in cooling as we moved from the first to the second and then to the third model. The spectral distributions of AOD have been used to derive Angstom parameters and this help us to determine the nature of the aerosols size distribution and increase in RH shows increase in mode size distributions. Using regression analysis, the Angstrom exponents were determined along with α1 and α2, the coefficients of a second order polynomial fit. The analysis further shows that these aerosols have bimodal type of particle distributions with Junge type as dominant.