Analysis of the Impact of Relative Humidity and Mineral Nuclei Mode Aerosols Particle Concentration on the Visibility of Desert Aerosols

This paper presents the results of the Analysis of the Impact of relative humidity and water-soluble aerosol particle concentrations on the visibility and particle size distribution of desert aerosols based on microphysical properties of desert aerosols. The microphysical properties (the extinction coefficients, volume mix ratios, dry mode radii and wet mode radii) were extracted from Optical Properties of Aerosols and Clouds (OPAC 4.0) at eight relative humidities (00 to 99%RH) and at the spectral range of 0.4-0.8 mm. the concentrations of mineral nuclie component (MINN) were varied to obtain five different models. The angstrom exponent ( a ), the turbidity ( b ), the curvature ( a 2 ), humidification factor ( g ), the mean exponent of aerosol growth curve ( µ ) and the mean exponent of aerosol size distributions ( n ) were determined from the regression analysis of some standard equations. It was observed that the values of ( a ) are less than 1 throughout the 5 models which signifies the dominance of coarse mode particles over fine mode particles. It was observed that the curvature ( a 2 ) has both monomodal and bimodal types of distributions all through the 5 models and this signifies the dominance of coarse mode particles with some traces of fine mode particles. The visibility was observed to decrease with the increase in RH and increased with wavelength. The analysis further found that there is an inverse power law relationship between humidification factor, the mean exponent of the aerosol size distribution with the mean exponent of the aerosol growth curve (as the magnitude of ( µ ) decreases across the five models, the magnitudes of ( g ) and ( n ) increase, but the magnitude of both ( g ) and ( n ) increases for a given ( µ ) across the individual models). The mean exponent of aerosol size distribution ( µ ) being less than 3 indicate hazy condition of the desert atmosphere.