Quality Controlling Surfzone Acoustic Doppler Velocimeter Observations to Estimate the Turbulent Dissipation Rate
Abstract
High-quality measurements of the turbulent dissipation rate are required to diagnose field surfzone turbulence budgets. Quality control (QC) methods are presented for estimating surfzone with Acoustic Doppler Velocimeter (ADV) data. Bad ADV velocity data points are diagnosed with both the ADV signal-strength (SS) and correlation (CORR). The fraction of bad SS data points (SS) depends inversely upon the wave-amplitude normalized transducer distance below the mean sea-surface. The fraction of bad CORR data points CORR can be elevated when SS is low. The CORR depends inversely upon the wave-amplitude normalized sensing volume distance below the mean sea-surface and also increases with increased wave-breaking, consistent with turbulence and bubble induced Doppler noise. Velocity spectra derived from both "patched" and "interpolated" time series is used to estimate. Two QC tests, based upon the properties of a turbulent inertial-subrange, are used to reject bad data runs. The first test checks that the vertical velocity spectrum's power-law exponent is near 5/3. The second test checks that a ratio R of horizontal and vertical velocity spectra is near one. Over all CORR, 70% of patched and interpolated data runs pass these tests. However, for larger CORR > 0.1 (locations higher in the water column) 50% more patched than interpolated data runs pass the QC tests. Previous QC methods designed for wave studies are not appropriate for QC. The results suggest that they can be consistently estimated over the lower 60% of the water column and > 0.1 m above the bed within a saturated surfzone.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 15, 2010
- Accession Number
- ADA516028
Entities
People
- Falk Feddersen
Organizations
- Scripps Institution of Oceanography