AEROSOL OPTICAL DEPTH FROM SPECTRAL DIRECT NORMAL IRRADIANCE MEASUREMENTS IN MONTEVIDEO, URUGUAY

This paper presents a novel technique to extract starlight signals from all-sky images and retrieve aerosol optical depth (AOD). It is validated against lunar photometry, showing a strong correlation between data series. This innovative approach will expand nocturnal AOD measurements to more locations, as all-sky cameras are a simpler and more cost-effective alternative to stellar and lunar photometers.

Several techniques retrieve of the aerosol size distribution. The Generalized Retrieval of Atmosphere and Surface Properties algorithm can retrieve aerosol size distribution parameters using only aerosol optical depth (AOD) as input that is continuously observed by sun photometers worldwide. In this study, we apply the algorithm to AOD measured by sun photometers and spectroradiometers to assess the performance and limitations of such retrievals and investigate the effect of the spectral range.

Large-scale retrievals of the ultraviolet index (UVI) in real time by exploiting the modern Earth observation data and techniques are capable of forming operational early warning systems that raise awareness among citizens of the health implications of high UVI doses. In this direction a novel UVI operating system, the so-called UVIOS, was introduced for massive outputs, while its performance was tested against ground-based measurements revealing a dependence on the input quality and resolution.