Multifractal analysis of the earth oblateness and Length-Of-Day fluctuations

Abstract

Geodynamic processes acting on the Earth’s system continuously modify the redistribution of the Earth’s mass. As a result, various inherent global physical parameters, including the gravitational field of the Earth and its variability, as well as the Earth’s rotation rate and variations often observed in Length-Of-Day (LOD), are affected. The Earth’s gravity field is described by a set of spherical harmonic functions derived from a combination of various satellite data as well as terrestrial observations. These functions act as proxy parameters that contribute towards our understanding of the dynamics of the Earth’s system. One of the most important spherical harmonic coefficients of the gravity field of the Earth is the even zonal harmonic coefficient J 2 . This coefficient is used to describe the Earth’s flattening due to mass distribution between the Earth’s Equator and the polar regions, and is therefore a measure of the Earth oblateness. The J 2 coefficient exhibits spatial-temporal variations which are often correlated with LOD variations. The aim of this contribution is to use the fractal nature of J 2 and LOD to demonstrate that their variability is not characterized by well-defined scales (of time) that play dominant roles, but rather involve all scales equally. Characterizing the variability of J 2 and LOD using the fractal paradigm will enhance our understanding of the complex geophysical processes of the Earth system.