Investigation of Aerosol Single Scattering Albedo in the Ultraviolet Spectrum

Abstract

Single scattering albedo (ω), the ratio of scattering coefficient to total extinction coefficient, at UV wavelengths is an important aerosol radiative parameter in determining surface UV irradiance. Surface measurements of total and diffuse UV irradiance in the summer and fall of 1999 at the seven narrowband wavelength channels of an UV multifilter rotating shadowband radiometer (UVMFR-SR) at Black Mountain, NC were coupled with a tropospheric ultraviolet radiative transfer model to produce values of ω. Its value ranged from 0.53 – 0.94 at 300 nm to 0.55 – 1.00 at 368 nm. Error in this procedure decreases with increasing aerosol optical depth (AOD), from +/-0.19 at AOD = 0.05 to +/-0.02 at AOD=1.0. Values of ω were not found to be correlated with air mass origin. The current values of ω have a wider variation than values reported from a previous study at the same site, possibly attributable to changes in aerosol chemical composition over time. The value of ω was found to be quadratically correlated with wavelength. Little research has been conducted in the scattering and absorption properties of aerosols in the UV wavelengths, but what has been done suggests such a correlation is possible. More values of ω in the UV spectrum will allow for better estimation of this parameter for UV radiative transfer modeling and will lessen error in estimation of surface UV irradiances.