To study the Earth’s rotation and its variation, i.e. precession, nutation, polar motion (PM) and the length-of-day (LOD), based on modern space geodetic data and geodynamical theory. In these theoretical models, the solid Earth, the oceans, and the atmosphere are treated together as a dynamical system. Such models are able to follow the interaction of the motion of all sub-surface and surface geophysical fluids (the atmosphere, oceans, and hydrological cycle, amongst others); as well as the physical structure of the Earth’s interior and the processes at play within. Such models allow for the investigation of variations in the Earth’s rotation on various spatial and temporal scales. We also apply these models to other planets.

What we have done, and what we are studying:

The relationship between the Earth’s rotation, Solar activity, and natural disasters such as earthquakes have been investigated, and results used to make predictions. For example, a non-linear stochastic excitation model for the Chandler wobble has been proposed.

Other research topics include: the theory of non-rigid Earth rotation, especially nutation; geodynamics; and the physics of the Earth’s interior, including differential rotation, coupling between the electro-magnetic field, and nutation. A new nutation model for a non-rigid Earth has been derived, and generalized spherical harmonics (GSH) and their application to theoretical geophysics is also one of our interests. For example, a set of scalar equations of infinitesimal elastic-gravitational motion for the fluid outer core of a rotating, slightly elliptical planet such as the Earth has been derived. This model has also been applied to Mars.

An explicit analytic solution of Poincare’s equation for the motion of a rotating, spherical fluid body has been derived. In addition, a new analytic theory for the generation of zonal multiple-jet flows on the basis of the nonlinear interaction of slowly travelling and non-axisymmetric geostrophic waves in Jupiter’s atmosphere has been presented.

In order to study planetary dynamics and geodynamics, we have set up a numerical simulation laboratory, in which the most significant resource is a PC cluster. Through carrying out simulations on our cluster with a code written to run on parallel computers, our research continues to make significant strides in progress.

Leading Professor: Xinhao Liao