Mathematical functions that cut up data into different frequency components, and then study each component with a resolution matched to its scale. Wavelet analysis is a statistical tool for analysing such localized variations of power within a time series. By decomposing a time series into time–frequency space, it is possible to determine the dominant modes of variability and how those modes vary in time. Torrence and Compo (1998) Bull. Amer. Meteor. Soc., 79, 61 provide a practical step-by-step guide to wavelet analysis, and Kumar (1997) Rev. Geophys. 35, 4 outlines the possibilities of wavelet analysis in physical geography (see Barrett and Houser (2012) Phys. Geog. 33, 1, 32).

paos.colorado.edu/research/wavelets Papers and some software outlining wavelet analysis.