Abstract
Global Navigation Satellite System (GNSS) meteorology, in which the zenith total delay (ZTD) and precipitable water vapor (PWV) are retrievable from GNSS signals, is a well-established tool for weather and climate monitoring. The real-time provision of ZTD/PWV products has always been challenging in GNSS meteorology, which is basically limited by the timely accessibility to precise satellite ephemerides. GNSS open service is based on the broadcast ephemerides. The accuracy of Galileo broadcast ephemerides has been improved to a high level, enabling real-time retrieval of ZTD/PWV using Galileo open service and being independent of network communication environments and devices. Moreover, building additional data processing systems and dense ground tracking networks is no longer necessary (excluding issues necessitating extremely accurate real-time ZTD/PWV retrievals, such as the PWV along coastal boundaries). We propose the real-time precise point positioning (PPP) technology with Galileo broadcast ephemerides to retrieve the high-accuracy ZTD/PWV. The data sets from 22 globally distributed stations spanning a year are used for analysis. Results indicate that the accuracy of real-time ZTD estimates derived from ambiguity-float solutions can reach to 2 cm after an average initialization time of 52.9 min. Taking international GNSS service (IGS) and radiosonde results as the reference, the mean bias of ZTD and PWV errors is usually less than 6 and 2 mm, respectively, while the standard deviation (STD) is 15.7 and 2.5 mm. The performance of ZTD/PWV estimates is nearly comparable to that of IGS real-time data streams, while it is worse than that of IGS post-processed precise products.
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Data availability
The datasets at selected MGEX stations, the broadcast ephemerides, the post-processed precise products from WHU, and the ZTD products provided by IGS can be obtained from ftp://igs.gnsswhu.cn. The real-time precise products from CNES can be obtained from http://www.ppp-wizard.net/products/REAL_TIME/. The NCEP GFS forecast products can be downloaded for free at the website https://rda.ucar.edu/datasets/ds084.1/. The IGRA radiosonde data are freely accessible via the link http://www1.ncdc.noaa.gov/pub/data/igra/.
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Acknowledgements
The authors would like to thank the IGS for providing GNSS data sets and the National Oceanic and Atmospheric Administration for providing the IGRA radiosonde data. We also thank the National Centers for Environmental Prediction/National Weather Service/NOAA/U.S. Department of Commerce for contributing the NCEP GFS data. This research was funded by the National Natural Science Foundation of China (Grant No. 41904030), and the Natural Science Foundation of Hunan Province, China (Grant No. 2020JJ5706).
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All authors contributed to the study and design. LP and MD performed material preparation, data collection, and analysis. LP and BC wrote the first draft of the manuscript, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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Pan, L., Deng, M. & Chen, B. Real-time GNSS meteorology: a promising alternative using real-time PPP technique based on broadcast ephemerides and the open service of Galileo. GPS Solut 28, 113 (2024). https://doi.org/10.1007/s10291-024-01659-x
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DOI: https://doi.org/10.1007/s10291-024-01659-x