Simulation of Historic and Future Atmospheric Angular Momentum Effects on Length-of-day Variations with GCMs

  • Timo Winkelnkemper
  • Florian Seitz
  • Seung-Ki Min
  • Andreas Hense
Part of the International Association of Geodesy Symposia book series (IAG SYMPOSIA, volume 133)


This paper focuses on atmospheric wind-driven effects on changes in length-of-day (δLOD). A 20th century simulation has been carried out using the ECHAM5 standalone atmosphere general circulation model (GCM). The spectrum of the resulting time series for δLOD shows typical structure patterns which resemble geodetic observations

Furthermore a future scenario run for the period 2000–2100 driven by SRES A1B forcing scenario shows a strong increase in the axial atmospheric angular momentum (AAM) which implies a lengthening of the LOD. For the scenario runs the coupled atmosphere ocean GCM ECHO-G has been used. The extent of the simulated changes in axial AAM exceeds results from former studies. By 2100 the model shows an increase in axial AAM of about 10 percent compared to present day conditions. The strongest trends in zonal windspeed are detected in the Southern Hemisphere for mid and higher latitudes in the upper troposphere. The reason for this trend can be found in the thermal wind equation. The westerly winds in high levels are directly related to the magnitude of the horizontal, north-south, gradient in temperature averaged from the Earth’s surface to the height of the level. The future scenario runs show significant strengthening in this gradient at higher levels


Atmospheric angular momentum (AAM) Earth rotation Length-of-day (LOD) Atmospheric excitation Climate change GCM ECHAM5 ECHO-G 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Timo Winkelnkemper
    • 1
  • Florian Seitz
    • 2
  • Seung-Ki Min
    • 3
  • Andreas Hense
    • 1
  1. 1.Meteorological Institute University of BonnGermany
  2. 2.Earth Oriented Space Science and Technology (ESPACE)Technische Universität MünchenGermany
  3. 3.Climate Research Division Environment CanadaTorontoCanada

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