Report on the EARLINET database versioning control system and data traceability

The European Aerosol Research Lidar Network, EARLINET, established in 2000 as a research project, has the goal of creating a quantitative, comprehensive, and statistically significant database for the horizontal, vertical, and temporal distribution of aerosols on a continental scale. Since then EARLINET has continued to provide the most extensive collection of ground-based data for the aerosol vertical distribution all over Europe (Pappalardo et al., 2014). At present, 31 stations distributed all over Europe are part of the network. A strong link with EARLINET data users has been established since the beginning of EARLINET in which EARLINET people acted as mentor and guide for users to assure a correct use and interpretation of the data. This was from one side a big effort for the EARLINET community as a whole,on the other side it was the opportunity to improve the knowledge about the user needs. In April 2010 a user web portal was made accessible to the public and since that date more than 3 and a half million products data files have been downloaded from the database. The number of registered external users has grown up year by year and nowadays this number is about 500. External users are spread all over the world, in particular, on 46 countries (16 out of Europe). EARLINET is a key component of the ACTRIS infrastructure (Aerosols, Clouds and Trace gases Research Infrastructure), which represents a big step towards a better coordination of the atmospheric observations in Europe towards the establishment of the European component of an Integrated Atmospheric Global System as part of GEOSS, the Global Earth Observation System of Systems (GEOSS, 2005). EARLINET is also a contributing network to the GAW Programme. The EARLINET database, also, takes advantage from the centralized data processing through the common standardized automatic analysis software developed within EARLINET, the Single Calculus Chain (SCC) (D'Amico et al., 2015). It is also possible the submission of data analyzed by using specific Quality Assured (QA) and documented software. The usage of the SCC assures the usage of QA retrieval algorithms and the full traceability of all EARLINET products. Currently the EARLINET database is the largest and most representative database of aerosol optical parameters obtained from LIDAR measurements on continental scale. It is freely available and it made possible several studies of atmospheric aerosols on European scale. In order to guarantee the highest possible quality of the final products, and at the same time to ensure the homogeneity of data from different types of lidar systems, EARLINET/ACTRIS network has implemented a rigorous quality assurance program that all affiliated stations are expected to meet (Freudenthaler et al., 2018; Matthais et al., 2004). The implementation of the quality assurance program has been, and still is, one of the main activities of EARLINET/ACTRIS network, and is a prerequisite to establish and monitor over time the performance of different Lidar systems that are part of the network. The quality control of EARLINET applies to both lidar instruments and analysis algorithms levels. Nowadays the EARLINET database is facing a complete reshaping to meet the wide request for more intuitive products and to face the even wider request related to the new initiatives such as Copernicus, the European Earth observation programme. The new design has been carried out in continuity with the past, to take advantage from long-term database. In this report we describe the EARLINET database Record Version Control system. Sometimes it can happen that a product already uploaded on the database is not fully optimized, moreover, products may need to be re-analysised if, for example, new retrieval algorithms are released. With the aid of a Record Version Control system it will be allowed (among others) to version a product, that is, allowing a product to exist in several versions at the same time.