Journal of Geodesy

, Volume 90, Issue 2, pp 179–188 | Cite as

Elliptic polarisation of the polar motion excitation

  • Christian BizouardEmail author
Original Article


Because of its geophysical interpretation, Earth’s polar motion excitation is generally decomposed into prograde (counter-clockwise) and retrograde (clockwise) circular terms at fixed frequency. Yet, these later are commonly considered as specific to the frequency and to the underlying geophysical process, and no study has raised the possibility that they could share features independent from frequency. Complex Fourier Transform permits to determine retrograde and prograde circular terms of the observed excitation and of its atmospheric, oceanic and hydrological counterparts. The total prograde and retrograde parts of these excitations are reconstructed in time domain. Then, complex linear correlation between retrograde and conjugate prograde parts is observed for both the geodetic excitation and the matter term of the hydro-atmospheric excitation. In frequency domain, the ratio of the retrograde circular terms with their corresponding conjugate prograde terms favours specific values: the amplitude ratio follows a probabilistic gamma distribution centred around 1.5 (maximum for 1), and the argument ratio obeys a distribution close to a normal law centred around \(2 \alpha = 160^{\circ }\). These frequency and time domain characteristics mean an elliptical polarisation towards \(\alpha ={\sim } 80^{\circ }\) East with an ellipticity of 0.8, mostly resulting from the matter term of the hydro-atmospheric excitation. Whatsoever the frequency band above 0.4 cpd, the hydro-atmospheric matter term tends to be maximal in the geographic areas surrounding the great meridian circle of longitude \({\sim }80^{\circ }\) or \({\sim } 260^{\circ }\) East. The favoured retrograde/prograde amplitude ratio around 1.5 or equivalently the ellipticity of 0.8 can result from the amplification of pressure waves propagating towards the west by the normal atmospheric mode \(\Psi _3^1\) around 10 days.


Earth’s rotation Polar motion  Hydro-atmospheric excitation Elliptical polarisation 



We are grateful to our three reviewers for their careful analysis, which permitted to improve the quality of this study. We are especially indebted to Leonid Zotov for having carried out some computational check.


  1. Barnes RTH, Hide R, White AA, Wilson CA (1983) Atmospheric angular momentum fluctuations, length-of-day changes and polar motion. Proc R Soc Lond A 387:31–73CrossRefGoogle Scholar
  2. Bizouard C (2014) Le mouvement du pôle de l’heure au siècle. Presses Académiques Francophones, p 284Google Scholar
  3. Bizouard C, Gambis D (2008) The combined solution C04 for Earth Orientation Parameters, recent improvements. In: Drewes H (ed) Series International Association of Geodesy Symposia 134. Springer Verlag series, p 330. ISBN: 978-3-642-00859-7Google Scholar
  4. Brzeziński A (1994) Polar motion excitation by variations of the effective angular momentum function, II: extended model. Manuscr Geod 19:157–171Google Scholar
  5. Brzeziński A, Bizouard C, Petrov S (2002) Influence of the atmosphere on Earth rotation: what new can be learnt from the recent atmospheric angular momentum estimates? Surv Geophys 23:33–69CrossRefGoogle Scholar
  6. Lambeck K (1980) The Earth’s variable rotation : geophysical causes and consequences. Cambridge University PressGoogle Scholar
  7. Munk WH, Mac Donald G (1960) The rotation of the Earth. Cambridge University Press, CambridgeGoogle Scholar
  8. Nastula J, Salstein D, Kolaczek B (2009) Patterns of atmospheric excitation functions of polar motion from high resolution regional sectors. J Geophys Res 114:B04407. doi: 10.1029/2008JB005605 Google Scholar
  9. Nastula J, Salstein D, Gross R (2014) Regional Multi-fluid-based geophysical. excitation of polar motion. In: Rizos C, Willis P (eds) Earth on the edge: science for a sustainable planet. International Association of Geodesy Symposia 139. Springer-Verlag, Berlin, Heidelberg (2014). doi: 10.1007/978-3-642-37222-3-62
  10. SBA (2015) Website of the IERS Special bureau for the atmosphere.
  11. SBH (2015) WEB site of the IERS special bureau for hydrology.
  12. SBO (2015) WEB site of the IERS special bureau for the oceans.
  13. Sidorenkov N (2009) The interaction between Earth’s rotation and geophysical processes, Wiley-VCH Verlag GmbH&Co., Chapter 6, p 113–118. ISBN 978-3-527-40875-7Google Scholar
  14. Vondrák J (1977) Problem of smoothing observational data II. Bull Astron Inst Czech 28:84–89Google Scholar
  15. Wilson C (1985) Discrete polar motion equation. Geophys J R Astron Soc 80(2):551–554CrossRefGoogle Scholar
  16. Zotov L, Bizouard C (2012) On modulations of the Chandler wobble excitation. J Geodyn. doi: 10.1016/j.jog.2012.03.010
  17. Zotov L, Bizouard C (2014) Regional atmospheric influence on the Chandler wobble. Adv Space Res. Elsevier. doi: 10.1016/j.asr.2014.12.013

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Observatoire de Paris, SYRTE/UMR 8630ParisFrance

Personalised recommendations