Wave Measurement Intercomparison and Platform Evaluation during the ITOP (2010) Experiment

Abstract

Spectral wave parameters from 11 platforms, measured during the recent Impact of Typhoons on the Ocean in the Pacific (ITOP) experiment, are intercompared. Two moorings, separated by ;180 km, were deployed in a section of ''typhoon alley'' off the coast of Taiwan for 4 months. Each mooring consisted of an Air-Sea Interaction Spar (ASIS) buoy that was tethered to a moored Extreme Air-Sea Interaction (EASI) buoy. EASI, the design of which is based on the hull of a 6-m Navy Oceanographic Meteorological Automatic Device (NOMAD) buoy, is validated as a 1D wave sensor against the established ASIS. Also, during this time three drifting miniature wave buoys, a wave-measuring marine radar on the Research Vessel Roger Revelle, and several overpasses of Jason-1 (C and Ku bands) and Jason-2 (Ku band) satellite altimeters were within 100 km of either the northern or southern mooring site. These additional measurements were compared against both EASI buoys. Findings are in-line with previous wave parameter intercomparisons. A corroborated measurement of mean wave direction and direction at the peak of the spectrum from the EASI buoy is presented. Consequently, this study is the first published account of directional wave information that has been successfully gathered from a buoy with a 6-m NOMAD-type hull. This result may be applied to improve operational coverage of wave direction. A high level of confidence is established in the ITOP wave data. Advantages and disadvantages of the different sensor types are discussed, which may be useful for the design of future field experiments.

Observations of Surface Wave Dispersion in the Marginal Ice Zone

“…Although the exact amount of icing was not measured, Figure shows a relatively thin layer of ice surrounding the buoy that represents a modest increase in total volume of the buoy. The increase in diameter is unlikely to alter size‐filtering effect of the buoy, where the highest frequency measured is limited to that of twice the buoy length (e.g., Collins et al, ). The heave response frequency was 3.80 Hz, so the mass or draft would have to increase by more than 50X for it to approach the highest frequency measured.…”

Directional Wave Spectra Observed During Intense Tropical Cyclones

“…Cross correlating the slope and heave signals recorded by the buoy gives the cospectra and quadrature spectra. EASI‐S had an error in one component of the compass signal requiring a slightly different method for determining the cospectra and quadrature spectra (see Collins et al, , Appendix )). The cospectra and quadrature spectra are directly related to the first two directional moments (also known as the first five directional coefficients: [ A 0 ( f ), A 1 ( f ), B 1 ( f ), A 2 ( f ), B 2 ( f )]; Kuik et al, ; Longuet‐Higgins et al, ).…”

Calibrating a Viscoelastic Sea Ice Model for Wave Propagation in the Arctic Fall Marginal Ice Zone

“…The real part of the wavenumber is determined by two independent methods. One applies the ‘slope method’ based on the cross‐correlation of the heave‐pitch‐roll signal to estimate the low‐order directional moments and an estimate of the root‐mean‐square wavenumber (Longuet‐Higgins et al, ; Appendix of Kuik et al, ; Collins et al, ). This method is applied to the WB buoy datasets only, with formula given in the Appendix , equation .…”