Quantifying wave measurement differences in historical and present wave buoy systems

Robert Edward Jensen,Richard Harry Bouchard,Val Swail

doi:10.1007/s10236-021-01461-0

Abstract

An intra-measurement evaluation was undertaken, deploying a NOMAD buoy equipped with three National Data Buoy Center and two Environment and Climate Change Canada-AXYS sensor/payload packages off Monterey, California; a Datawell Directional Waverider buoy was deployed within 19 km of the NOMAD site. The six independent wave measurement systems reported hourly estimates of the frequency spectra, and when applicable, the four Fourier directional components. The integral wave parameters showed general agreement among the five sensors compared to the neighboring Datawell Directional Waverider, with the Inclinometer and the Watchman performing similarly to the more sophisticated 3DMG, HIPPY, and Triaxys sensor packages. As the Hm0 increased, all but the Inclinometer were biased low; however, even the Watchman reported reasonable wave measurements up to about 6–7 m, after which the Hm0 becomes negatively biased up to about a meter, comparable to previous studies. The parabolic fit peak spectral wave period, Tpp, results showed a large scatter, resulting from the complex nature of multiple swell wave systems compounded by local wind-sea development, exacerbated by a variable that can be considered as temporally unstable. The three directional sensors demonstrated that NOMAD buoys are capable of measuring directional wave properties along the western US coast, with biases of about 6 to 9 deg, and rms errors of approximately 30 deg. Frequency spectral evaluations found similarities in the shape, but a significant under estimation in the high frequency range. The results from slope analyses also revealed a positive bias in the rear face of the spectra, and a lack of invariance in frequency as suggested by theory.

Highlights

Wind-generated surface gravity waves have been measured by various systems for more than six decades (Cavaleri et al.This article is part of the Topical Collection on the 16th International Workshop on Wave Hindcasting and Forecasting in Melbourne, AU, November 10-15, 2019 Responsible Editor: Jose-Henrique Alves2018)
The second cause for the large number of deviations in the parabolic fit peak period (Tpp) results can be attributed to defining the peak energy in the spectrum for low wave height conditions
Given all of the subtleties in the collection procedure, the inherent unstable nature defining the peak wave period over time, results from FLOSSIE are relatively consistent with the Directional Waverider (DWR)

Summary

Introduction

Wind-generated surface gravity waves have been measured by various systems for more than six decades (Cavaleri et al.This article is part of the Topical Collection on the 16th International Workshop on Wave Hindcasting and Forecasting in Melbourne, AU, November 10-15, 2019 Responsible Editor: Jose-Henrique Alves2018). Small minidrifter buoys capable of returning non- and directional wave measurements (Thomson 2012; Collins III et al 2014; Centurioni et al 2017) have been incorporated into operations, adding to the spatial coverage of the world’s oceans. These assets complement the long-term use of satellite-based remote sensing systems (including aircraft) used to map estimates of the significant wave height, or estimate the directional wave properties (Synthetic Aperture Radars) spatially over the ocean surface (Ardhuin et al 2019)

Results

Discussion

Conclusion