IGPP Seminar Series

New perspectives and methodologies for scaling research in hydro-geomorphology

by Dr. Efi-Foufoula-Georgiou
National Center for Earth-surface Dynamics and St. Anthony Falls Laboratory, Dept. of Civil Engineering, University of Minnesota


In this talk we will give an overview of new directions (both methodological and conceptual) in multiscale data analysis, illustrating our concepts with the recent results in scaling research in hydro-geomorphology. The presented methods and ideas though have a broader applicability for complex systems of different origin. We re-examine the scaling structure of temporal rainfall using wavelet-based methodologies which, as we demonstrate, offer important advantages compared to the more traditional multifractal approaches such as box counting and structure function techniques. In particular, we explore two methods based on the Continuous Wavelet Transform (CWT) and the Wavelet Transform Modulus Maxima (WTMM): the partition function method and the newer and more efficient magnitude cumulant analysis method. We also report the results of a two-point magnitude correlation analysis which is able to infer the presence or absence of multiplicativity as the underlying mechanism of scaling. The diagnostic power of these methodologies for small samples, signals with short ranges of scaling, and signals for which high frequency fluctuations are superimposed on a low-frequency component (all common attributes of geophysical signals) is carefully documented. Application of these methodologies to several midwestern convective storms sampled every 5 seconds over several hours provide new insights. Another application to be discussed is the analysis of the so-called ?width function? which summarizes the branching topology of river networks and which exhibits multifractal characteristics.
Tuesday, 14 March 2006
3845 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM