27th IUGG General Assembly July 8-18, 2019 Montreal, Canada Comparing atmospheric data and models at station Wettzell during CONT17 Daniel Landskron1, Johannes Böhm1, Thomas Klügel2, Torben Schüler2 1 Technische Universität Wien, Austria 2 Federal Agency for Cartography and Geodesy, Geodetic Observatory Wettzell, Germany

Overview (1) Comparison between a variety of atmospheric datasets over station WETTZELL, Germany between Nov 28 and Dec 12, 2017 In situ pressure data Radiosonde data Numerical weather model data GNSS estimates VLBI estimates Water vapor radiometer data 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Overview (2) zhd: zenith hydrostatic delay in situ, NWM, Radiosonde zwd: zenith wet delay Radiosonde, NWM, GNSS, VLBI, WVR shd + swd: slant delay hydrostatic + wet Radiosonde, NWM (VMF3+VMF1) 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Mapping function from radiosonde data? All TU Wien troposphere mapping functions (VMF3, VMF1, GPT3, GMF) are based on ray-tracing through NWM data Mapping functions can likewise be determined from radiosonde data NWM Radiosonde mfh + mfw globally mfh + mfw locally 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Mapping function from radiosonde data! Dense 2D model of atmosphere above the station Densified through interpolation 1D ray-tracing yields zhd, zwd, mfh and mfw b and c coefficients from VMF3 => a coefficients Local mapping function from radiosonde data 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Pre-comparison steps All data reduced to hell = 666 m dh = 8 m ≈ dp = 1 hPa ≈ dzhd = 2.5 mm Different temporal resolutions: In situ: every minute Radiosonde: twice daily at ~08:00 and ~14:00 NWM: six-hourly GNSS: hourly VLBI: hourly WVR: every minute Interpolation 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Results: Zenith Hydrostatic Delay Δzhd w.r.t. in situ [mm] Bias σ VMF3 -3.0 1.8 VMF1 -0.7 1.7 NCEP -0.4 0.9 RS => All solutions show very good agreement 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Results: Zenith Wet Delay (1) Δzwd w.r.t. Radiosonde [mm] Bias σ VMF3 -0.8 5.4 VMF1 0.5 5.5 NCEP -5.0 4.1 GNSS -1.6 4.2 WVR -6.2 12.2 VLBI 2.3 => Generally very good agreement, except for outliers in WVR data 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Results: Zenith Wet Delay (2) Δzwd w.r.t. Radiosonde [mm] Bias σ GNSSBKG -1.6 4.2 GNSSWETT -6.3 5.2 VLBI 2.3 4.1 => Estimations from GNSS and VLBI are very similar 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Results: Slant Hydrostatic Delay at 5° Δshd w.r.t. Radiosonde [mm] Bias σ VMF3 -27.5 18.5 VMF1 -3.3 18.1 Zenith delays from Radiosonde: [mm] Bias σ VMF3 -0.5 5.5 VMF1 0.2 4.8 => Again very good agreement, but VMF1 has smaller bias than VMF3 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

Results: Slant Wet Delay at 5° Δswd w.r.t. Radiosonde [mm] Bias σ VMF3 -9.0 58.3 VMF1 4.7 58.9 Zenith delays from Radiosonde: [mm] Bias σ VMF3 -0.3 4.7 VMF1 1.1 1.4 => Worse agreement, but not surprising for the slant wet delay 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

What limits the accuracy Radiosondes do not ascend vertically Radiosonde profiles only 2D Radiosondes ascend for up to 90 min before they burst, but integrated value valid for launch time Height reductions Temporal interpolations with few sample values Outliers in WVR data => Results are absolutely pleasant, sub-mm not necessary! 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)

And finally… Feel free to use this extensive meteorological dataset by the Geodetic Observatory WETTZELL: https://doi.pangaea.de/10.1594/PANGAEA.895518 2019/07/16 Comparing atmospheric data and models at station Wettzell during CONT17 (Landskron et al., 2019)