Improving Current Measurements from Wave Buoys: Results from a Successful Five-Year Collaborative Development Project

Abstract

Recognizing that detailed analyses of the accuracy of acoustic current profiles from instruments mounted on dynamic surface platforms (MetOcean or wave buoys) were lacking, the authors and colleagues began studying the issue in 2014. Initial testing with an ADCP mounted on a spherical wave buoy showed significant errors when compared with multiple bottom-mounted wave/current profilers. We initiated a repeated cycle of testing, analysis, reporting, and instrument improvement, with subsequent test deployments in 2015-2016, 2017-2018, and 2018-2019. Results from the first three of these have been reported in detail at previous OCEANS conferences and other technical workshops (IEEE CWTM, MTS Buoy Workshops) – see References [1]–[5] The process has led to evolutionary improvements to both the wave/current buoy design (AXYS TRIAXYS) and current profiler performance for buoy integration (NORTEK Signature AD2CP with AHRS). The resulting integrated platform was deployed under test conditions from December 2018 – March 2019. Preliminary comparisons show that the improvements have resulted in buoy-based current profiles that accurately match bottom-mounted profiles far better than previous versions (under the test conditions, 12-25 m depths, $0-2\ \boldsymbol{m\ H_{s}}, > 1\boldsymbol{m}/\boldsymbol{s}$ currents with significant vertical shear). Here we present results and analyses of the 2018-2019 deployments, which consisted of two TRIAXYS buoys (new design with central profiler mount and NORTEK Signature, an older offset profiler design with a NORTEK Aquadopp), and a nearby NORTEK AWAC current/wave profiler.