NATIONAL REPORT OF THE FEDERAL REPUBLIC OF ... - IAG Office

Introduction
The determination of Earth rotation is one of the main tasks
of geodesy. Variations of Earth rotation due to the redistribution
of masses within the Earth system are closely
related to the deformation of the geometric shape of the
Earth and the temporal variations of its gravity field.
The report on the activities of German scientists in Earth
rotation and geodynamics research during the period 2003
to 2007 is subdivided in the following sections:
– Crustal deformation and Geodynamics,
– Earth Tides and Non-tidal Gravity Field Variations,
– Geophysical Fluids,
– Earth Rotation – Theory and Analysis,
– Sea Level and Ice Sheets,
– International Earth Rotation and Reference Systems
Service (IERS).
German scientists contributed in various ways to the
objectives of IAG commission 3, which is described in the
above mentioned sections. Here, only a few examples for
intensive research activities are given.
In Germany, geodesy has a long-standing tradition in
research and education. It serves as a bridging discipline
within the geosciences and has often been the driving factor
in organising larger research projects. This also holds for
Earth Rotation and Geodynamics.
Earth Rotation
The rotation of the Earth does not only relate the terrestrial
and the quasi-inertial reference systems to each other;
moreover, its variations contain essential features of global
dynamic processes. Correspondingly, Earth rotation
research is multi-disciplinary with a close interrelation
between modelling, observation, and analysis. The Earth
has to be considered as a complex system of interacting
dynamic components. The variations of Earth rotation are
global and integral indicators of ongoing changes in the
dynamics of the Earth, both for the redistribution of masses
inside and outside the Earth and for mass motions like wind
and oceans currents (see SCHUH et al. 2003).
The German Earth rotation community succeeded in 2006
to allocate funds for a so-called research unit “Earth rotation
and global dynamic processes” of the DFG (Deutsche
Forschungsgemeinschaft – German Research Foundation).
The main objective of this coordinated research unit is to
describe and explain the physical phenomena which
Overview and Highlights
J. MÜLLER 1
1 Jürgen Müller: Leibniz Universität Hannover (University of Hannover), Institut für Erdmessung (Institute of Geodesy), Schneiderberg 50,
D - 30167 Hannover, Germany, Tel. +49 - 511 - 762-3362, e-mail mueller@ife.uni-hannover.de
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contribute to variations of Earth rotation. Interactions and
couplings of the various sub-systems are taken into account
and dedicated analyses of the dynamic processes are carried
out.
The research unit is coordinated by J. MÜLLER (also
chairman), H. KUTTERER, both University of Hannover and
M. SOFFEL, Technical University of Dresden. It is composed
by scientists and institutions from geodesy, geophysics,
meteorology and oceanography. The unit is
organized in ten thematic projects which are
– Earth rotation and information system: Development of
a virtual Earth rotation system for geodetic and geoscience
applications (ERIS),
– Earth rotation and ocean circulation,
– Consistent post-Newtonian nutation series of a ‘rigid’
Earth model,
– Mass motions in the Earth’s core and mantle and their
influence on polar motion and the gravity field,
– Lunar Laser ranging: Consistent modeling for geodetic
and scientific applications,
– Integration of Earth rotation, gravity field and geometry
using space geodetic observations,
– Modelling of episodic-transient signals in measurements
of large ring lasers,
– Investigation of sub-daily and episodic variations of
Earth rotation,
– Usability of time-variable Earth orientation parameters
and gravity field coefficients from satellite missions for
mutual validation and combined analysis,
– Long-term ERP time series as indicator for global
climate variability and climate change.
More information on the DFG Research Unit FOR584 can
be obtained from http://www.erdrotation.de.
In a second research initiative, an earth system model for
the simulation of variations of earth rotation, deformation
and gravity field, which are induced by atmospheric,
oceanic and hydrological processes and their interaction,
has been developed (see THOMAS et al., in this report).
Geodynamics
A further joint research project, mainly motivated by the
successful performance of GRACE and its overwhelming
input for Earth system research was prepared by ILK et al.
(2005), which resulted in a so-called DFG priority programme
“Mass transport and mass distributions in the system