Geophysical loading effects on station positions and EOP from VLBI data analysis

Geodätische Woche – Session 1: Geodätische Bezugssysteme

Stuttgart, September 15th, 2015

Kyriakos Balidakis1, S. Glaser1, D.D. Wijaya2, B. Soja3,

M. Karbon3, T. Nilsson3, R. Heinkelmann3 and H. Schuh1,3

kyriakos.balidakis@tu-berlin.de

1Technische Universität Berlin, Institut für Geodäsie und Geoinformationstechnik, Berlin, Deutschland2Geodesy Research Group, Bandung Institute of Technology, Indonesia

3Geodäsie und Fernerkundung, Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Deutschland

. . . setting the stage

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Outline

Investigate the impact of applying: different atmospheric pressure loading (APL) models

the sum of all non-tidal loading constituents (atmospheric/non-tidal ocean/hydrological loading) from different providers

in VLBI data analysis for site position and Earth orientation parameters

Investigate the calculation of displacements induced by APL Surface pressure fields

Green’s functions

Ocean response to pressure forcing

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Services for

Predicted elastic mass loading displacements

provider APL NTOL CWS

GFZ Sektion 1.3 - -LSDM(24h)

VLBI group at NASA/GSFC NCEP/NCAR Reanalysis (6h)

ECCO kf080(12h)

GLDAS/Noah (monthly)

IMLS MERRA/NASA (6h)

OMCT (6h)MERRA/NASA

(3h)

Université du Luxembourg NCEP Reanalysis(6h)

ECCO kf080(12h)

GLDAS(monthly)

Université de Strasbourg ERA-Interim Reanalysis (6h)

ECCO kf080(12h)

GLDAS/Noah (6h)

Technische Universität Wien ECMWF operational (6h)

- -

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

Gravitational consistency and mass conservation on surface loads are beyond the intended scope of this talk. Hence, we simply add . . .

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Predicted elastic mass loading displacements

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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VLBI data analysis

Vienna VLBI Software, VieVS@GFZ (Gauß-Markov model)

Interferometric group delay data from IVS-R1 and IVS-R4 from 2002 until 2015 (1324 sessions) featuring a 32 station network

All displacement models are applied at observation level

10 solutions produced: Reference solution (abides to IERS conventions 2010)

5 solutions for different APL models

4 solutions for the sum of all non-tidal loading constituents

All solutions determined w.r.t. ITRF2008and IERS EOP 08 C04 series

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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VLBI analysis (position)

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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VLBI analysis (position)

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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VLBI analysis (baselines)

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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VLBI analysis (EOPs)

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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VLBI analysis (EOPs)

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Calculation of deformations due to atmospheric pressure loading

We assume: Purely elastic deformations alone

The elastic properties of the Earth do not differ laterally

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

ΔP: surface pressure anomaly

𝐺𝑟 and 𝐺ℎ: radial and lateral Green’s function

𝜑 and 𝜆: geodetic latitude and longitude of the site

𝜓: spherical distance between the point mass load and the site

𝛼: azimuth angle between the point mass load and the site

𝑢𝑟 𝒓, 𝑡 = 𝛥𝑃 𝒓′, 𝑡 𝐺𝑟 𝜓 cos 𝜑′ 𝑑𝜆′𝑑𝜑′

𝑢𝐸𝑊 𝒓, 𝑡 = 𝛥𝑃 𝒓′, 𝑡 𝐺ℎ 𝜓 sin 𝑎𝒓𝒓′ cos 𝜑′ 𝑑𝜆′𝑑𝜑′

𝑢𝑁𝑆 𝒓, 𝑡 = 𝛥𝑃 𝒓′, 𝑡 𝐺ℎ 𝜓 cos 𝑎𝒓𝒓′ cos 𝜑′ 𝑑𝜆′𝑑𝜑′

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Numerical Weather Model data sets

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Barometric adjustment

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Geoid undulation and Orography

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Load Love Numbers and Green’s functions

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Load Love Numbers and Green’s functions

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Load Love Numbers and Green’s functions

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Load Love Numbers and Green’s functions

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Load Love Numbers and Green’s functions

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Ocean response to pressure forcing

Non-inverted barometer

Inverse barometer

Modified inverse barometer

Dynamic sea level

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Ocean response to pressure (and wind) forcing

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

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Recapitulation Applying geophysical loading models at the observation level is beneficial for

VLBI in terms of WRMS reduction of position and baseline length series, as well as variance of EOP series.

Best models for APL: from the University of Strasbourg

Green’s functions choice not negligible

Barotropic ocean models improve the performance of APL models

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

Outlook Establish online service

Investigate different Numerical Weather Models (e.g. MERRA)

Consider the gravitational consistency and mass conservation

More investigations concerning Green’s functions (e.g. local from Dill et al., 2015)

Perform tests to other space geodetic techniques (GNSS & SLR)

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Selected references

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

Böhm, J., S. Böhm, T. Nilsson, A. Pany, L. Plank, H. Spicakova, K. Teke and H. Schuh. The new Vienna VLBI Software VieVS, in Proceedings of IAG Scientific Assembly 2009, International Association of Geodesy Symposia Series Vol. 136, edited by S. Kenyon,M. C. Pacino, and U. Marti, pp. 1007-1011, 2012, doi: 10.1007/978-3-642-20338-1_126

Carrère L. and F. Lyard (2003) Modeling the barotropic response of the global ocean to atmospheric wind and pressure forcing –comparisons with observations. Geophys Res Lett 30(6):1275.doi: 10.1029/2002GL016473

Claessens S.J. and C. Hirt (2013) Ellipsoidal topographic potential: New solutions for spectral forward gravity modeling of topography with respect to a reference ellipsoid, Journal of Geophysical Research - Solid Earth, Vol. 118(11), 5991-6002, doi: 10.1002/2013JB010457

Dee, D.P. and 40 others (2011) The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q.J.R. Meteorol. Soc., 137: 553–597. doi: 10.1002/qj.828

Förste, C., S.L. Bruinsma, O. Abrikosov, J.-M. Lemoine, J.-C. Marty, F. Flechtner, G. Balmino, F. Barthelmes and R. Biancale (2015) EIGEN-6C4 The latest combined global gravity field model including GOCE data up to degree and order 2190 of GFZ Potsdam and GRGS Toulouse. GFZ German Research Center for Geosciences. http://dx.doi.org/10.5880/icgem.2015.1

Schuh, H. and D. Behrend (2012) VLBI: A fascinating technique for geodesy and astrometry, Journal of Geodynamics, Vol. 61, pp. 68–80, October 2012. doi: 10.1016/j.jog.2012.07.007

Petrov, L. and J.-P. Boy (2004), Study of the atmospheric pressure loading signal in very long baseline interferometry observations, J. Geophys. Res., 109, B03405, doi: 10.1029/2003JB002500

van Dam, T., Z. Altamimi, X. Collilieux and J. Ray (2010) Topographically induced height errors in predicted atmospheric loading effects, J. Geophys. Res., 115, B07415, doi: 10.1029/2009JB006810

Wang, H., L. Xiang, L. Jia, L. Jiang, Z. Wang, B. Hu and P. Gao (2012) Load Love numbers and Green's functions for elastic Earth models PREM, iasp91, ak135, and modified models with refined crustal structure from Crust 2.0, Computers & Geosciences, Volume 49, December 2012, Pages 190-199, ISSN 0098-3004, http://dx.doi.org/10.1016/j.cageo.2012.06.022

Wijaya, D.D, J. Böhm, M. Karbon, H. Krásná and H. Schuh (2013) Atmospheric pressure loading, in J. Böhm and H. Schuh (eds): Atmospheric Effects in Space Geodesy, Springer Verlag, pp. 137-157, doi: 10.1007/978-3-642-36932-2_4, 2013

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kyriakos.balidakis tu-berlin.de

AcknowledgementsIVS for coordinating the VLBI experiments used in this work

ECMWF for making publicly available the ERA-Interim reanalysis data setsGFZ, GSFC, Université du Luxembourg, Université de Strasbourg, Technische Universität Wien and IMLS for

making publicly available displacement time seriesKB is supported by DVW-AK7 and by the DFG project ECORAS (HE 5937/2-1)

Balidakis et al.: Geophysical loading effects on station positions and EOP from VLBI data analysis

Thank you for your attention!

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