Geoscience Reference
In-Depth Information
Atmospheric Effects on Earth Rotation
Michael Schindelegger, Sigrid Böhm, Johannes Böhm and Harald Schuh
Abstract
One of the pivotal sources for fluctuations in all three components of the
Earth's rotation vector is the set of dynamical processes in the atmosphere, per-
ceptible as motion and mass redistribution effects on a multitude of temporal and
spatial scales. This review outlines the underlying theoretical framework for study-
ing the impact of such geophysical excitation mechanisms on nutation, polar motion,
and changes in length of day. It primarily addresses the so-called
angular momentum
approach
with regard to its physical meaning and the application of data from numer-
ical weather models. Emphasis is placed on the different transfer functions that are
required for the frequency-dependent intercomparison of Earth rotation values from
space geodetic techniques and the excitations from the output of atmospheric cir-
culation models. The geophysical discussion of the review assesses the deficiencies
of present excitation formalisms and acknowledges the oceans as other important
driving agents for observed Earth rotation variations. A comparison of the angular
momentum approach for the atmosphere to an alternative but equivalent modeling
method involving Earth-atmosphere interaction torques is provided as well.
