Doppler Correction of Wave Frequency Spectra Measured by Underway Vessels
Abstract
“Sea State and Boundary Layer Physics of the Emerging Arctic Ocean” is an ongoing Departmental Research Initiative sponsored by the Office of Naval Research (http://www.apl.washington.edu/project/project.php?id=arctic_sea_state). The field component took place in the fall of 2015 within the Beaufort and Chukchi Seas and involved the deployment of a number of wave instruments, including a downward-looking Riegl laser rangefinder mounted on the foremast of the R/V Sikuliaq. Although time series measurements on a stationary vessel are thought to be accurate, an underway vessel introduces a Doppler shift to the observed wave spectrum. This Doppler shift is a function of the wavenumber vector and the velocity vector of the vessel. Of all the possible relative angles between wave direction and vessel heading, there are two main scenarios: 1) vessel steaming into waves and 2) vessel steaming with waves. Previous studies have considered only a subset of cases, and all were in scenario 1. This was likely to avoid ambiguities, which arise when the vessel is steaming with waves. This study addresses the ambiguities and analyzes arbitrary cases. In addition, a practical method is provided that is useful in situations when the vessel is changing speed or heading. These methods improved the laser rangefinder estimates of spectral shapes and peak parameters when compared to nearby buoys and a spectral wave model.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 01, 2017
- Source ID
- 10.1175/jtech-d-16-0138.1
Entities
People
- A. Kohout
- B. Blomquist
- Björn Lund
- C. Fairall
- C. O. Collins
- Dafu Wang
- Erick Erick Rogers
- H. C. Graber
- J. Thomson
- M Doble
- Mathew Smith
- O. Persson
- Peter Wadhams
Organizations
- American Society for Engineering Education
- National Institute of Water and Atmospheric Research
- National Oceanic and Atmospheric Administration
- Office of Naval Research
- United States Naval Research Laboratory
- University of Cambridge
- University of Miami
- University of Washington