An Evaluation of Aerosol Optical Depth Using Stellar Photometry.

Aerosols impact climate, weather, and astronomical measurements by scattering and absorbing stellar radiation. Daytime Aerosol Optical Depth (AOD) is commonly measured as part of the NASA AERONET network of robotic sun photometers, however, nighttime measurements are rare. Nighttime measurements of AOD are important for air quality monitoring, for correcting astronomical observations, for quantifying column average aerosol size distributions for use in radiative transfer calculation of night time infrared radiative impacts of aerosol, and possibly for studying noctilucent clouds. Stellar spectral photometer measurements from a CCD camera at Nevada’s Great Basin Observatory were utilized to observe five standard photometric stars to determine the total aerosol optical depth of the atmosphere at night. AOD measurements were obtained by subtracting light extinction caused by Rayleigh scattering and the absorption by gases in the atmosphere from the total measured spectral extinction. Multi spectral stellar AOD allows for retrieval of column average aerosol size distribution at night.