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

This study validates two ceilometer aerosol retrieval methods (backward and forward methods) using GRASP and COBALD balloon measurements across three European sites under different aerosol regimes. The forward method systematically outperforms the backward approach, reducing AOD uncertainties by ~50 % under high aerosol loads. Results demonstrate that forward retrievals with independent calibration significantly improve operational ceilometer network performance for aerosol monitoring.

We perform Photovoltaic (PV) power simulations with the Global Solar Energy Estimator and assess the uncertainty linked to the use of a diffuse fraction model. Validation is conducted under diverse atmospheric conditions, including cloudiness and aerosols, using input data from ground-based measurements and the Copernicus Atmosphere Monitoring Service (CAMS). Results indicate that simulations are reliable under most conditions, with overestimations occurring during intense dust events.

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.

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.

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.