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Abstract

Permanent GNSS stations provide invaluable observations to remote sensing atmospheric water vapour. Studies show that it helps to improve the accuracy of weather forecast, including the prediction of severe weather events. Moreover, longer time series of GNSS tropospheric products can contribute to climate studies, too. One of these products is the zenit tropospheric delays (ZTDs), that are routinely estimated using GNSS observations. Zenith wet tropospheric delays well correlate with the atmospheric integrated water vapour.This paper focuses on the tomographic reconstruction of atmospheric water vapour leading to a three-dimensional model of the water vapour density over the study area. The slant wet delays are calculated using the estimated zenith delays, tropospheric gradients and the applied mapping function and the 3D wet refractivity model is calculated using an algebraic reconstruction technique. Recently, a near realtime GNSS tomography system has been developed for the territory of the Pannonian basin by the authors that provides not only ZTD estimates but also 3D refractivity models on an hourly basis using GPS, GLONASS and Galileo observations. This study focuses on the assimilation of these products in numerical weather models. One year of ZTD estimates and refractivity profiles are compared to ECMWF ERA5 reanalysis data to assess the quality of the products, and a seasonal model is derived to estimate their accuracy.Furthermore, both the ZTDs and the refractivity profiles are assimilated in a numerical weather model covering the Pannonian basin. The results are validated using ECMWF ERA5 reanalysis products and local meteorological observations.