The rotary multiple filter technique and its application in the analysis of ocean current data

The Multiple Filter Technique (MFT) is a filtering technique, which is used to investigate variations in the amplitude and phase of dispersive signals in the time (t), and frequency f) domain. The paper extends the MFT to process current vector time series. The rotary MFT is applied to investigate the evolution of nonlinear wave-wave interactions observed in the ocean. The purpose of the present paper is twofold, namely: I) to review the MFT method, and apply it to deal with rotary components of ocean vectors, and, II) to describe applications of the rotary MFT to examine the evolution of energies at different frequencies in the ocean current time series, especially the nonlinear interactions of internal waves in the ocean. The rotary MFT is demonstrated to be an effective tool for analyzing the current time series data.