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Robert Heinkelmann
Type of contribution: oral

Atmospheric refractivity gradients from VLBI compared to those from GNSS, DORIS, WVR, and NWM

Robert Heinkelmann Galina Dick Tobias Nilsson Benedikt Soja Florian Zus Jens Wickert Harald Schuh

There is a long tradition of incorporating geodetic atmospheric parameters into meteorological and climatological models. A prominent example is the operational assimilation of GNSS based zenith delays into numerical weather models (NWM) to improve global and regional weather forecasts. GFZ is one of the leading institutions in atmosphere sounding using GNSS and has been contributing since more than 15 years within various meteorological and geodetic research projects to these developments. GFZ is also in charge of the IVS (International VLBI Service for Geodesy and Astrometry) troposphere products that currently include total and wet zenith delays. These are used for routine comparisons, e.g., by the IGS (IGS Troposphere Working Group) and by EUREF. Within the EU COST Action GNSS4SWEC (GNSS for monitoring Severe Weather Events and Climate) one focus lies on the provision of atmospheric refractivity gradients to add information on the horizontal distribution of the atmospheric parameters compared to the zenith delays. Data from the CONT14 campaign were used as a test case for the comparison of atmospheric gradients and their corresponding formal errors obtained by VLBI with the following techniques: GNSS, DORIS, water vapor radiometer (WVR), and three different solutions obtained from the weather models NCEP and ECMWF. We summarize initial results of our investigations to determine VLBI based atmospheric gradients and to provide estimations on their precision. Our investigations demonstrate that the VLBI technique shows great potential for obtaining accurate atmospheric gradients. In particular, w.r.t. the upcoming VGOS (VLBI Global Observing System) we expect to deliver atmospheric gradients from VLBI with very good accuracy and high temporal resolution.