Ground-based GNSS data processing for atmospheric water vapor retrieval at Wuhan University and some applications

Wuhan University has joined the E-GVAP program as one of the analysis centers (ACs) since 2019. Data at about 300 global GNSS stations are routinely processed in near-real-time at Wuhan University for tropospheric delay product. Both the single GPS solution and the recent multi-GNSS (GPS/GLONASS/Galileo/BDS) solution have been delivered to E-GVAP. Besides the near-real-time processing, we also work on the long-term historical data reprocessing for climate research and on the real-time processing for atmospheric monitoring. In the reprocessing work, by taking the recent ERA5 and homogenized radiosonde data as reference, we have made comprehensive investigations on the impacts of different models (e.g., the mapping function) and settings (e.g., the cut-off elevation angle) using global data of more than two decades. The long-term water vapor product was used for climate analysis and for inter-comparisons among different techniques (GNSS, radiosonde, reanalysis, MODIS, etc.). In the real-time processing work, we have carried out a four-month real-time water vapor retrieval campaign in three cities of China in 2021 by including the latest BeiDou-3 satellites and by using the high-accuracy satellite product transmitted by BeiDou-3 GEO satellites on the B2b signal. The data processing work in reprocessing, near-real-time and real-time modes at Wuhan University will be systematically introduced and some applications in climate research and atmospheric monitoring will be presented.