This dataset collects ACTRIS/EARLINET data collected during a special measurement campaign held in May 2020 as part of the ACTRIS initiative for studying the changes in the atmosphere during the COVID-19 lockdown. As an active contributor to ACTRIS, EARLINET run its lidars and intensified its regular measurements in the early relaxation period in May 2020.

An intensive observation campaign was organized in May 2020. Measurements were collected following a specific schedule (each day, two times per day: a) around noon; b) after sunset). Data was processed in a centralized way using the Single Calculus Chain (SCC), with specific configurations and settings, and was made publicly available in near-real time (NRT). Data was afterwards reprocessed to take into consideration the results of the quality assurance tests and the model reanalysis, in order to improve the quality of the final products. The same procedure was applied to all datasets included here.

Data is classified as Level 1 and Level 2 data. Level 2 data is compliant to all the QC procedures currently working on the ACTRIS/EARLINET database. Level 1 data is data of lower quality since they fail at least 1 of the advanced quality controls running on the ACTRIS/EARLINET database. Particular attention should be paid using Level 1 data.