# The HD(CP)\({}^{2}\) Data Archive for Atmospheric Measurement Data
## 1 Introduction  
To develop climate change strategies, it is essential to understand how the earth's climate system works, to notice climate changes as well as their causes. The understanding progress is based on observed and simulated climate data, whereby the data from climate simulation models is one of the fastest growing segments in the data world [1]. The process of cloud formation and regional precipitation is critical for simulating atmospheric dynamics, and therefore for climate prediction. Both clouds and precipitation are important elements of the climate system [2]. Almost every physical process in the earth system, from soil-moisture feedback to sea-ice interaction to biogeochemical interaction, depends critically on clouds and the hydrologic cycle. The project \"High definition clouds and precipitation for advancing climate prediction\" is a German-wide research initiative to improve our understanding of cloud and precipitation processes and their implication for climate prediction. The project is funded by the German Federal Ministry of Education and Research (BMBF) and started in October 2012. In the first project phase, the observation and simulation domain of HD(CP)\({}^{2}\) was concentrated on Germany and border regions. In the second phase, which has recently started, the domain has been enlarged by a tropical zone (Barbados). Whereas the model developers designed a climate model capable of high-resolution simulations, the observation component organizes ground, in situ and satellite-based observations in order to evaluate the model results. The measurements are concentrated on spatial structure and cloud particle composition, using existing measuring facilities all over Germany and the Netherlands. Along with the increasing volume and importance of climate data, the responsibility of data producers and data publishers has also grown [3]. Besides the establishing of reliable data archives,it is important to make them more easy to use. In HD(CP)2 the demand for easy usability was part of the project proposal. A brief data management plan was included, describing the requirements on data storage, data documentation, data policy and standard formatting for data producers, data publishers and data users. For example, all observation component partners were requested to deliver their collected data to the archive. The willingness to share the data with the scientific community was a prerequisite for participation in the project. The mandatory data archiving policy should remove barriers to effective data sharing. In general, data sharing allows other scientists to verify the data, and use it for reproducing model results, validating interpretations, and building upon the work of the project research [4]. A data archive is more than a collection of datasets; besides the data, the archive should include documentation, a physical store of the information and meta-information, and a user interface [5]. Within the project, the implementation of such a data management system (DMS) is mainly performed at the Regional Computing Centre of the University of Cologne (RRZK). The established DMS takes into consideration the practical recommendations given in the \"Handbuch Forschungsdatenmanagement\" which was designed to help face the general challenges in data management [6]. The RRZK is one project partner in HD(CP)2 responsible for technical infrastructure and support. A computing center is specialized to provide data management services and support storage infrastructure in order to ensure a high level of quality and a sustainable basis for further development in the post-project phase. Most scientists have neither the resources, with regard to time and cost, nor the technical support to maintain an archive. In fact, the lack of technical support and structural funding are the most often-named threats to common digital data preservation [7]. An important reason for the establishment of a new data archive was the lack of a common infrastructure for the detailed supersite observations in Germany.