Extracting wind sea and swell from directional wave spectra derived from a bottom-mounted ADCP

Abstract

Recent advances in processing velocity data from bottom-mounted Acoustic Doppler Current Profilers (ADCPs) offer the capability of partitioning directional wave specctra of surface wave height in order to separate locally generated wind waves from swell. In the study described here, we have partitioned directional wavee spectra, derived from bottom-mounted ADCP measurements at the Martha’s Vineyard Coastal Observatory (MVCO) south of Martha’s Vineyard, MA, into dominant swell and locally generated wind-wave components. The partitioning was carried out following the method of Hanson and Phillips (2001) using an exploratory approach. As part of tthis approach, we assessed the validity of the ADCP-derived wave spectra by comparing them with one-dimensional wavee spectra derived from laser altimeter measurements. This comparison identified a frequency range over which the ADCP-derived wave field may be suspeect. We also carried out a series of sensitivity tests in which we evaluated how the results of wave partitioning according to the Hanson and Phillips (2001) method is influenced by varying the parameters required to implement the method. In this report, we describe and assess the data sources used in our study, outline the methods employed for wave spectra partitioning and describe partitioning results.