Day- and night-time aerosol optical depth implementation in CÆLIS

• Main Authors: González, Ramiro, Toledano, Carlos, Román, Roberto, Fuertes, David, Berjón, Alberto, Mateos, David, Guirado-Fuentes, Carmen, Velasco-Merino, Cristian, Antuña-Sanchez, Juan Carlos, Calle, Abel, Cachorro, Victoria E., Frutos, Ángel M.
• Format: Text
• Language: English
• Published: 2020
• Subjects: Aerosol Robotic Network
• Online Access: https://doi.org/10.5194/gi-2020-19; https://gi.copernicus.org/preprints/gi-2020-19/

The University of Valladolid (UVa, Spain) manages since 2006 a calibration center of the AErosol RObotic NETwork (AERONET). The CÆLIS software tool, developed by UVa, was created to manage the data generated by the AERONET photometers, for calibration, quality control and data processing purposes. This paper exploits the potential of this tool in order to obtain products like the aerosol optical depth (AOD) and Angstrom exponent (AE), which are of high interest for atmospheric and climate studies, as well as to enhance the quality control of the instruments and data managed by CÆLIS. The AOD and cloud screening algorithms implemented in CÆLIS, both based on AERONET version 3, are described in detail. The obtained products are compared with the AERONET database. In general, the differences in daytime AOD between CÆLIS and AERONET are far below the expected uncertainty of the instrument, ranging the mean differences between −1.3×10 −4 at 870 nm and 6.2×10 −4 at 380 nm. The standard deviations of the differences range from 2.8×10 −4 at 675 nm to 8.1×10 −4 at 340 nm. The AOD and AE at night-time calculated by CÆLIS from Moon observations are also presented, showing good continuity between day and night-time for different locations, aerosol loads and moon phase angles. Regarding cloud screening, around 99.9 % of the observations classified as cloud-free by CÆLIS are also assumed cloud-free by AERONET; this percentage is similar for the cases considered as cloud-contaminated by both databases. The obtained results point out the capability of CÆLIS as processing system. The AOD algorithm provides the opportunity to use this tool with other instrument types and to retrieve other aerosol products in the future.