The Computation of Climatological Power Spectra

Abstract

A technique for computing climatological power spectra based on the concept of utilizing non-integer values in the sine and cosine waveforms (NI technique) is developed and applied to climatological rainfall data. This technique provides a powerful alternative to the more common techniques used in the computation of climatological power spectra. The major advantage of this technique is the greatly improved resolution of wavelengths in the 5–25 year region, often a critical region of interest for climatologists. The technique produces spectral density values which are not necessarily independent; however, methods of specifying and then testing the departure from independence (orthogonality) are given. Furthermore, it is shown that the usual equations for the Fourier coefficients are special cases of the more general condition in which the spectral estimates include some degree of non-independence (i.e., lack of orthogonality). It is anticipated that this technique will have wide applicability in climatology, meteorology, hydrology and the other geophysical sciences.