Advances in Physics Theories and Applications www.iiste.org ISSN 2224-719X (Paper) ISSN 2225-0638 (Online) DOI: 10.7176/APTA Vol.79, 2019 21 The Effect of Varying Water Soluble Components on the Radiative Forcing of Continental Average Aerosols Bello Idrith Tijjani 1 , Bello 2 M,A. U.Muhammad,M.G Ahmad, R.S Said 1 1.Department of Physics,Bayero University, Kano, Nigeria 2.Department of Physics , Federal University, Gusau, Nigeria Abstract This work embodies the results of the effect of the water soluble components on the radiative forcing of continental average aerosols, from aerosol data extracted from optical properties of aerosols and cloud (OPAC) 4.0 software package using FORTRAN program to model the effect of water soluble on optical depth, asymmetric parameter, scattering and absorption coefficients at the spectral range of (0.25-0.80µm) and at eight relative humidities (0%,50%,70%,80%,90%,95%,98% & 99%). The concentration of water soluble was varied while concentrations of water insoluble and soot were kept constant. The optical parameters were used to compute numerically the radiative forcing using the concept of chylek and wong, the Angstrom exponent (α), turbidity (β) and Curvature (2) using regression analysis with SPSS 20.0 IBM. From the results obtained it was observed that α which determined the particle size distribution is greater than 1.0 at (0%-95%) RHs and it signifies that fine accumulation mode is the most dominant but at deliquescence points (98%-99%) RHs α is less than 1.0 and this show the present of coarse mode. The curvature 2 which gives additional information of particle mode distributions was negative at all RHs indicating the dominance of fine mode particles. The optical depth of the atmospheric aerosols were determined for each model and analyzed graphically, the results have shown the clear decrease in size with increase in wavelength, but increases with increase in RHs. The turbidity β increase with increases in concentration number of water soluble signifies the increases in aerosol loading which show decrease in visibility of the atmosphere. The analysis further shows that these aerosols have monomodal type of particle distributions. Keywords: Angstrom exponent, Curvature, Optical depth, Radiative forcing, Turbidity. DOI: 10.7176/APTA/79-04 Publication date:September 30 th 2019 1. Introduction Atmospheric aerosols, which are defined as liquid or solid particles suspended in a gas (Seinfeld and Pandis, 2006), are tiny and usually invisible to our eyes. Nevertheless, they have an immense impact on our health and on our global climate. Aerosol particles in the atmosphere which comprised both water soluble and insoluble aerosols, affect the earth’s radiation balance in both direct and indirect ways. The direct effect is influenced by the hygroscopicity of the aerosol particles, while the indirect is the tendency for cloud formation and resulting cloud properties all due to changes in Relative humidity (Solomon, S.et al., 2007; Tijjani et al., 2014). Aerosols scatter and absorb solar radiation, and, by doing so, they directly influence the Earth’s radiation budget. In addition, anthropogenic aerosol particles modify cloud properties, causing, e.g., brighter clouds with longer lifetimes and changed precipitation behavior (Lohmann and Leck, 2005; Ramaswamy et al., 2001; Twomey, 1977).. The net effect of anthropogenic aerosols on the Earth’s climate is cooling, in contrast to greenhouse gases, which have a warming effect (P.zieger et al.,2013). However, the Intergovernmental Panel on Climate Change (IPCC, 2007) concludes that the high uncertainty in the net radiative forcing of all main climate agents is mainly dominated by the large uncertainty in the aerosol radiative forcing. This is mainly caused by the high temporal, spatial, and compositional variability of the aerosol and the poorly understood and quantified aerosol effects. The water-soluble part of aerosol particles originates from gas to particle conversion and consist of various kinds of sulphate, nitrates and others also organic, water soluble substances. Thus, it contains more than only the sulphate aerosol that is often used to describe anthropogenic aerosol (Hess et al.,1998). Most of the earliest investigations on direct aerosol forcing focused on sulphate aerosol because of their importance as an anthropogenic aerosol component (Charlson et al.,1992, Kiehl and Briegleb, 1993). Sulphate particle is an important component of atmospheric aerosols. Sulphate aerosols are capable of modifying the climate not only by scattering incoming sunlight back to space (direct effect) but also by altering the properties of clouds (indirect effect) (Verma et al.,2012). The aim of this paper is to determine the effect of varying water soluble component on radiative forcing of continental average aerosols on three components of aerosols extracted from OPAC 4.0 software data set at the spectral range of 0.25-0.80µm and at eight relative humidity of (0%, 50%,70%,80%,90%, 95%,98% and 99%).