The Influence of Aerosol Chemistry on Spectral Aerosol Optical Properties During ARCTAS

Aerosols are noted to both absorb and scattering radiation at UV wavelengths with the degree of absorption/scattering largely dependent on aerosol chemistry. The interactions of aerosols with the UV radiation field were examined for several flights during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign in summer 2008. Aerosol single scattering albedo (ω) was retrieved at near-UV (300-400nm) wavelengths from spectral actinic flux data collected aboard the NASA DC-8 aircraft during ARCTAS using two CCD Actinic Flux Spectroradiometers. Retrievals were performed using the Tropospheric Ultraviolet Model versus 4.6 (TUV 4.6). TUV inputs of trace gas (e.g., NO2, SO2) concentrations, aerosol optical depth, location, time, pressure, etc. were determined from ancillary aircraft measurements made during ARCTAS. Values of ω were used to determine absorption optical depth (τabs) for each of the examined flights. Retrieval and calculation results were compared to aerosol optical properties in the visible and the spectral dependencies characterized. Additionally, comparisons of spectral ω and τabs with aerosol chemical data collected by an Aerosol Mass Spectrometer and teflon filters were performed and provide insight into the role of chemistry and enhanced absorption in the UV wavelength range.