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Throughout spring and summer 2020, ozone stations in the northern extratropics recorded unusually low ozone in the free troposphere. From April to August, and from 1 to 8 kilometers altitude, ozone was on average 7% (≈4 nmol/mol) below the 2000 to 2020 climatological mean. Such low ozone, over several months, and at so many stations, has not been observed in any previous year since at least 2000. Atmospheric composition analyses from the Copernicus Atmosphere Monitoring Service and simulations from the NASA GMI model indicate that the large 2020 springtime ozone depletion in the Arctic stratosphere contributed less than one quarter of the observed tropospheric anomaly. The observed anomaly is consistent with recent chemistry-climate model simulations, which assume emissions reductions similar to those caused by the COVID-19 crisis. COVID-19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020.

Throughout spring and summer 2020, ozone stations in the northern extratropics recorded unusually low ozone in the free troposphere. From April to August, and from 1 to 8 kilometers altitude, ozone was on average 7% (≈4 nmol/mol) below the 2000 to 2020 climatological mean. Such low ozone, over several months, and at so many stations, has not been observed in any previous year since at least 2000. Atmospheric composition analyses from the Copernicus Atmosphere Monitoring Service and simulations from the NASA GMI model indicate that the large 2020 springtime ozone depletion in the Arctic stratosphere contributed less than one quarter of the observed tropospheric anomaly. The observed anomaly is consistent with recent chemistry-climate model simulations, which assume emissions reductions similar to those caused by the COVID-19 crisis. COVID-19 related emissions reductions appear to be the major cause for the observed reduced free tropospheric ozone in 2020.

This paper discusses the multi-wavelength scanning Raman lidar being built at Lidar Division, CEILAP (CITEDEF-CONICET) in the frame of the Argentinean Cherenkov Telescope Array (CTA) collaboration to measure the spectral characteristics of the atmospheric aerosol extinction profiles to provide better transmission calculations at the future CTA site. This lidar emits short laser pulses of 7-9 ns at 355, 532 and 1064 nm at 50 Hz with nominal energy of 125 mJ at 1064 nm. This wavelengths are also used to retrieve the atmospheric (air, aerosol and clouds) backscattered radiation in the UV, VIS and IR ranges. Raman capabilities were added in the UV and VIS wavelengths to retrieve the spectral characteristics of the aerosol extinction and the water vapor profile. Due to the expected low aerosol optical depth of the future site, the short observation period as well as the extension of the observation, an enhanced collection area is required. This system uses six 40 cm f/2.5 newtonian telescopes to avoid dealing with bigger mirror deformation, aberration issues and higher costs that imply the use of a single mirror with the same collection surface. In addition, dismounting of single mirrors for replacement or recoating will affect slightly the performance but not the operation. The additional alignment procedure has been solved by an automatic mirror alignment to follow the line of sight of the observation during the acquisition period. The system was designed to operate in hard environmental conditions, as it is completely exposed to the outside weather conditions, when its shelter is fully opened to provide 360{\deg} observations., Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.2232

At CEILAP (CITEDEF-CONICET), a multiangle LIDAR is under development to monitor aerosol extinction coefficients in the frame of the CTA (Cherenkov Telescope Array) Project. This is an initiative to build the next generation of ground-based instruments to collect very high energy gamma-ray radiation (>10 GeV). The atmospheric conditions are very important for CTA observations, and LIDARs play an important role in the measurement of the aerosol optical depth at any direction. The LIDAR being developed at CEILAP was conceived to operate in harsh environmental conditions during the shifts, and these working conditions may produce misalignments. To minimize these effects, the telescopes comprising the reception unit are controlled by a self-alignment system. This paper describes the self-alignment method and hardware automation., Comment: In Proceedings of the "Atmospheric Monitoring for High EnergY Astroparticle Detectors" (AtmoHEAD 2013), Saclay (France)

At CEILAP (CITEDEF-CONICET), a multiangle LIDAR is under development to monitor aerosol extinction coefficients in the frame of the CTA (Cherenkov Telescope Array) Project. This is an initiative to build the next generation of ground-based instruments to collect very high energy gamma-ray radiation (>10 GeV). The atmospheric conditions are very important for CTA observations, and LIDARs play an important role in the measurement of the aerosol optical depth at any direction. The LIDAR being developed at CEILAP was conceived to operate in harsh environmental conditions during the shifts, and these working conditions may produce misalignments. To minimize these effects, the telescopes comprising the reception unit are controlled by a self-alignment system. This paper describes the self-alignment method and hardware automation., Comment: In Proceedings of the "Atmospheric Monitoring for High EnergY Astroparticle Detectors" (AtmoHEAD 2013), Saclay (France)

This paper discusses the multi-wavelength scanning Raman lidar being built at Lidar Division, CEILAP (CITEDEF-CONICET) in the frame of the Argentinean Cherenkov Telescope Array (CTA) collaboration to measure the spectral characteristics of the atmospheric aerosol extinction profiles to provide better transmission calculations at the future CTA site. This lidar emits short laser pulses of 7-9 ns at 355, 532 and 1064 nm at 50 Hz with nominal energy of 125 mJ at 1064 nm. This wavelengths are also used to retrieve the atmospheric (air, aerosol and clouds) backscattered radiation in the UV, VIS and IR ranges. Raman capabilities were added in the UV and VIS wavelengths to retrieve the spectral characteristics of the aerosol extinction and the water vapor profile. Due to the expected low aerosol optical depth of the future site, the short observation period as well as the extension of the observation, an enhanced collection area is required. This system uses six 40 cm f/2.5 newtonian telescopes to avoid dealing with bigger mirror deformation, aberration issues and higher costs that imply the use of a single mirror with the same collection surface. In addition, dismounting of single mirrors for replacement or recoating will affect slightly the performance but not the operation. The additional alignment procedure has been solved by an automatic mirror alignment to follow the line of sight of the observation during the acquisition period. The system was designed to operate in hard environmental conditions, as it is completely exposed to the outside weather conditions, when its shelter is fully opened to provide 360{\deg} observations., Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.2232