GNSS data from the geodetic receivers of global and regional ground networks are operationally analysed at GFZ in near-real time. The atmospheric data products, like zenith total delay and converted integrated water vapour above the ground stations, are provided for the operational assimilation to the weather prediction models and for special scientific investigations. Currently more than 500 GNSS stations are in the operational near-real time analysis (status as of September 2017), around 300 of them are from the German SAPOS network, others are from the European EUREF network as well as from the globally distributed IGS stations.
GFZ also supports temporary atmospheric measuring campaigns with the installation and operation of GNSS ground stations and corresponding data analysis. Specific data, as, e.g., slant delays in parallel from up to 30 navigation satellites, are currently used for studies to improve the precipitation forecast of the German Weather Service DWD [3].
The GNSS data of the GRUAN network (GCOS Reference Upper Air Network, www.gruan.org) of the WMO (World Meteorological Organization) are also analysed at GFZ and contribute to the GCOS (Global Climate Observing System). GNSS receivers are an integrated part of the observation equipment of the currently more than 20 globally distributed GRUAN observatories to investigate climatological variations of the Earth’s atmosphere [5]. Such information can also be derived from the German network. More than 100 stations provide data for more than 10 years, which can be used to reveal regional variations of the water vapour trends and to improve climate models [6].
The main methodological focus of the GFZ activities in GNSS meteorology is the improvement of the observation technique. Currently, this includes investigations related to the real-time data analysis and to transition from the single GPS to Multi-GNSS complemented by Galileo, GLONASS and BeiDou [7]. Another current focus is the detailed investigation of ionospheric propagation errors [8].
The GFZ activities in GNSS atmosphere sounding is performed within the Helmholtz Research field "Earth and Environment" in the programme "Atmosphere and Climate" in close cooperation with KIT and FZ Jülich.
[1] Ning, T., Wickert, J., Deng, Z., Heise, S., Dick, G., Vey, S., Schöne, T. (2016): Homogenized time series of the atmospheric water vapor content obtained from the GNSS reprocessed data. - Journal of Climate, 29, 7, p. 2443-2456, doi: 0.1175/JCLI-D-15-0158.1, 2016.
[2] Lu, C., Li, X., Zus, F., Heinkelmann, R., Dick, G., Ge, M., Wickert, J., Schuh, H., Improving BeiDou real-time precise point positioning with numerical weather models. - Journal of Geodesy, 91, 9, p. 1019-1029. doi 10.1007/s00190-017-1005-2, 2017.
[3] Zus, F., Dick, G., Heise, S., Wickert, J.: A forward operator and its adjoint for GPS slant total delays. - Radio Science, 50, 5, p. 393-405, doi: 10.1002/2014RS005584, 2015.
[4] Kačmařík, M., Douša, J., Dick, G., Zus, F., Brenot, H., Möller, G., Pottiaux, E., Kapłon, J., Hordyniec, P., Václavovic, P., and Morel, L.: Inter-technique validation of tropospheric slant total delays, Atmos. Meas. Tech., 10, 2183-2208, doi: 10.5194/amt-10-2183-2017, 2017.
[5] Ning, T., Wang, J., Elgered, G., Dick, G., Wickert, J., Bradke, M., Sommer, M.: The uncertainty of the atmospheric integrated water vapour estimated from GNSS observations. - Atmospheric Measurement Techniques, 9, p. 79-92, doi: 10.5194/amt-9-79-2016, 2016.
[6] Alshawaf, F., Balidakis, K., Dick, G., Heise, S., and Wickert, J.: Estimating trends in atmospheric water vapor and temperature time series over Germany, Atmos. Meas. Tech., 10, 3117-3132, doi.org/10.5194/amt-10-3117-2017 [doi.org], 2017.
[7] Li, X., Ge, M., Dai, X., Ren, X., Fritsche, M., Wickert, J., Schuh, H.: Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo. - Journal of Geodesy, 89, 6, p. 607-635, 2015.
[8] Zus, F., Deng, Z., Heise, S., Wickert, J.: Ionospheric mapping functions based on electron density fields. - GPS Solutions, 21, 3, p. 873-885, doi: 10.1007/s10291-016-0574-5, 2017.
