Atmospheric tides in variations of VLBI station positions

Transcription

1 / EGU7-89 / /9 in variations of VLBI station positions Anastasiia Girdiuk, Michael, Johannes Böhm TU Wien, Geodesy and Geoinformation, Vienna, Austria 4 April 7

2 in variations of VLBI station positions / EGU7-89 / / Very Long Baseline Interferometry (VLBI) analysis 4.

3 in variations of VLBI station positions / EGU7-89 / 3/9 : diurnal S and semidiurnal S Sun-locked have periods of 4 h and h : utilizes atmospheric in reductions; namely, station coordinates undergo small but regular deformations; retrieve atmospheric Petrov & Ma, 3, "Study of harmonic site position variations determined by very long baseline interferometry"; S and S in variations of station posistions?? Earth rotation

4 / EGU7-89 / 4/9 Station position reductions for tidal tidal loading (ATL): TU Wien: S & S tidal corrections S Radial component, mm: maximum for the frequently observing site: Katherine (Australia). mm

5 Station position reductions for tidal / EGU7-89 / 4/9 tidal loading (ATL): TU Wien: S Radial component, mm S and S tidal corrections to the station positions maximum for the frequently observing site: Katherine (Australia). mm Ocean tidal loading: Finite Element Solution: FES4 & FES (S ) Long term : Mf, Mm, Ssa; Major : Q, O, P, K, N, M, S, K

6 Station position reductions for tidal / EGU7-89 / 4/9 tidal loading (ATL): TU Wien: S Radial component, mm S and S tidal corrections to the station positions maximum for the frequently observing site: Katherine (Australia). mm Ocean tidal loading: Finite Element Solution: FES4 & FES (S ) max S : Fortaleza (South America). cm; max S : Katherine (Australia).4 mm

7 / EGU7-89 / 5/9 Tidal loading analysis in VLBI ATL maximum is achieved for Katherine (Australia); Observations in period of Jun, till Feb, 6 ( 365 gle observations); In contrast: ATL impact on Westford (North America) is considered as minimal

8 / EGU7-89 / 5/9 Tidal loading analysis in VLBI ATL maximum is achieved for Katherine (Australia); Observations in period of Jun, till Feb, 6 ( 365 gle observations); at least 5 stations per session: 3 %, 6 and more stations: 77 % In contrast: ATL impact on Westford (North America) is considered as minimal Observations in period of Jan, 995 till Sep, 4 ( 93 gle observations); at least 5 stations per session: 5 %, 6 and more stations: 84 %

9 : gle session solution / EGU7-89 / 6/9 the station of interest (Katherine or Westford) is excluded from the datum and the station coordinates are estimated hourly h stochastic parameters: hourly clock polynomials: h, tropospheric parameters: zenith wet delay: h 6 h, North & East gradients: 6 h, EOP, source and station coordinates per session (except Katherine or Westford) Standard approach ug Vienna Mapping Function, Ray-tracing (RT), Reducing correlations by fixing gradients

10 - RT gradients estimated; - Standard gradients estimated; σ; σ; - RT gradients fixed; - Standard gradients fixed; 3σ; tidal loading: S Radial, mm Ocean tidal loading: S radial, mm TUW Westford FES Westford Katherine TUW Katherine FES / EGU7-89 / 7/9

11 Amplitudes > by factor S > S tidal loading: S Radial, mm ocean estimates modeled A better agreement with FES Ocean tidal loading: S radial, mm TUW Westford FES Westford Katherine TUW Katherine FES / EGU7-89 / 7/9

12 Conclusion / EGU7-89 / 8/9 We derived empirical tidal loading model (S, S ) from VLBI observations for selected sites (Katherine, Westford); We find significant differences between VLBI observations and geophysical models. The origin is not quite clear; We find a better agreement of the major ocean (not shown); VLBI global solutions yield similar results.

13 Thank you for your attention! References: VLBI data: ivscc.gsfc.nasa.gov The recommended VLBI reductions are described by IERS Conventions iers.org FES station corrections: International Mass Loading Service massloading.net Hydrology loading: EOST Loading Service loading.u-strasbg.fr vievswiki.geo.tuwien.ac.at This study is supported by the Austrian Science Fund under project ASPIRE (I479). / EGU7-89 / 9/9