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Abstract. The present availability of 18+ years of GNSS data belonging to the EUREF Permanent Network (EPN, http://www.epncb.oma.be/) is a valuable database for the development of a climate data record of GNSS tropospheric products over Europe. This data record can be used as a reference for a variety of scientific applications (e.g. validation of regional numerical weather prediction reanalyses and climate model simulations) and has a high potential for monitoring trends and the variability in atmospheric water vapour. In the framework of the EPN-Repro2, the second reprocessing campaign of the EPN, five Analysis Centres homogenously reprocessed the EPN network for the period 1996-2014. A huge effort has been made to provide solutions that are the basis for deriving new coordinates, velocities and tropospheric parameters for the entire EPN. The individual contributions are then combined to provide the official EPN reprocessed products. This paper is focused on the EPN-Repro2 tropospheric product. The combined product is described along with its evaluation against radiosonde data and European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA-Interim) data.

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S U M M A R YTropospheric water vapour is the main limiting factor in using GPS to determine crustal deformation at highest accuracy. On the other hand, it is an important variable to monitor meteorological and climatic processes. This paper discusses both aspects: the modelling of tropospheric water vapour using meteorological data as well as the determination of the integrated amount of water vapour and its spatiotemporal variation using GPS data. Switzerland has been chosen as experiment area. The Swiss continuous GPS (CGPS) network AGNES is used as a reference network, which represents a realistic scenario for GPS-based water vapour determination. Data of the Swiss numerical weather model aLMo are used for systematic comparison and validation.For the first aspect, integrated tropospheric wet refractivity values are determined from meteorological measurements and compared with GPS path delays. An overall agreement of 1 cm of zenith wet path delay was achieved. For the second aspect a tomographic approach has been developed. A total of 6720 GPS-determined profiles are compared with data of the numerical weather model and radio soundings. The results are statistically evaluated and systematically compared with each other. A correlation between the accuracy and the weather situation was found. Overall, an agreement of 5-7 ppm (refractivity unit) was obtained compared to aLMo.The use of GPS-determined path delays from a permanent GPS network is the recommended method to correct GPS measurements. In all other cases, the two methods presented (COITROPA, COMEDIE) are a feasible alternative to determine path delays accurately. Furthermore, GPS is a convenient application to determine the amount of water vapour in the troposphere. It is demonstrated that the vertical distribution of water vapour can be deduced by applying the tomographic approach.