Moving Reference Systems

Abstract

In Chap. 2 it was assumed that balance equations were referred to an observer at rest in an inertial system. In this chapter our intention is not to concentrate on the issues like existence of such a reference system or on the ideas of constructing such a system, rather we presume that there exists such a reference system relative to which the quantities like momentum density, momentum supply and flux of momentum, as shown in Chap. 2, are uniquely defined. In the following, we shall demonstrate that the balance equations can also be formulated relative to an observer, which moves himself relative to a fixed observer, i.e., the observer performs a translatory and/or rotatory motion. In geophysical applications this situation arises quite frequently, because for a number of processes the Earth can not be identified with an inertial system. This implies that one must take the Earth’s motion in the respective equations into account and modify them accordingly. Theoretically, this can be done by introducing additional terms of the relative motion — Coriolis, centripetal and Euler accelerations. A change of the reference system, however, will also play an important role for the material equations as will be seen in Chap. 5.